Item Reduction and Psychometric Validation of the Oily Skin Self Assessment Scale (OSSAS) and the Oily Skin Impact Scale (OSIS)vhe_

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1 Volume 12 Number VALUE IN HEALTH Item Reductio ad Psychometric Validatio of the Oily Ski Self Assessmet Scale (OSSAS) ad the Oily Ski Impact Scale (OSIS)vhe_ Robert Arbuckle, MA, 1 Marci Clark, PharmD, 2 Jae Haress, MSc, 3 Nicola Boer, BSc, 1 Jae Scott, PhD, 1 Zoe Draelos, MD, 4 Roald Rizer, PhD, 5 Yatig Yeh, PhD, MA, 6 Kati Copley-Merrima, MS, MBA 2 1 Mapi Values, Bolligto, UK; 2 RTI-HS, Research Triagle Park, NC, USA; 3 Pfizer Ic, New Lodo, CT, USA; 4 Cliical Dermatology Ceter, High Poit, NC, USA; 5 Stephes & Associates, Colorado Sprigs, CO, USA; 6 Mapi Values, Bosto, MA, USA ABSTRACT Itroductio: Developed usig focus groups, the Oily Ski Self Assessmet Scale (OSSAS) ad Oily Ski Impact Scale (OSIS) are patietreported outcome measures of oily facial ski. Objective: The aim of this study was to fialize the item-scale structure of the istrumets ad perform psychometric validatio i adults with selfreported oily facial ski. Methods: The OSSAS ad OSIS were admiistered to 202 adult subjects with oily facial ski i the Uited States. A subgroup of 152 subjects retured, 4 to 10 days later, for test retest reliability evaluatio. Results: Of the 202 participats, 72.8% were female; 64.4% had selfreported osevere ace. Item reductio resulted i a 14-item OSSAS with Sesatio (five items), Tactile (four items) ad Visual (four items) domais, a sigle blottig item, ad a overall oiliess item. The OSIS was reduced to two three-item domais assessig Aoyace ad Self-Image. Cofirmatory factor aalysis supported the costruct validity of the fial item-scale structures. The OSSAS ad OSIS scales had acceptable item coverget validity (item-scale correlatios >0.40) ad floor ad ceilig effects (<20%). Crobach s alpha coefficiets raged from 0.83 to 0.89 for the OSSAS ad 0.82 to 0.87 for the OSIS, demostratig excellet iteral cosistecy. The a priori test retest reliability criterio (itraclass correlatio [ICC] 0.7) was met for oe of the three OSSAS domais ad oe of the two OSIS domais. OSSAS ad OSIS domais distiguished amog groups that differed i patiet-reported facial oily ski severity (P < ), ad bother associated with oily ski (P < ). Coclusios: The OSSAS ad OSIS versios tested i this study have bee foud to have strog psychometric properties i this patiet sample (adults with self-reported oily facial ski), as assessmets of self-reported oily facial ski severity ad its emotioal impact, respectively. Keywords: item reductio, oily ski, patiet-reported outcome, psychometric validatio, self-reported ace. Itroductio Oily ski or seborrhea (ICD-9 code 706.3), is characterized by excessive sebum productio which leads to a perso s ski appearig shiy ad greasy or oily [1 4]. Sebum overproductio is a importat causative factor i a variety of dermatologic diseases ad may be related to seborrheic dermatitis ad ace, thus oil cotrol is a importat part of the therapeutic regime for these coditios [5 7]. Oily facial ski, with ad without ace, ca have adverse psychological ad social cosequeces. Body image ca be affected ad may idividuals feel embarrassed ad aoyed because of the appearace of their oily ski [8,9]. Oily ski ca be difficult to treat as sebum mixes with topical medicatios ad cosmetics to destroy the film-formig properties ecessary for product fuctioig. I order to evaluate the efficacy of treatmets of oily facial ski i cliical trials, it is ecessary to have measures of oily facial ski severity that are valid, reliable, ad resposive to chages i oily ski. Few such measures curretly exist. I terms of cliical measures, the sebumeter ad sebutape are both widely used. However, the validity of both measures has ot yet bee uiversally stadardized ad there are o published guidelies for iterpretig the meaig of scores or the meaig of chages i scores. Address correspodece to: Robert Arbuckle, Patiet Reported Outcomes, Mapi Values Ltd., Adelphi Mill, Grimshaw Lae, Bolligto, Cheshire SK10 5JB, UK. rob.arbuckle@mapivalues.com /j x A patiet-reported outcome (PRO) istrumet developmet program was embarked upo with the aim of developig ad validatig PRO measures of oily facial ski that would meet curret stadards recommeded for PROs as outlied by regulatory authorities [10 12]. Two oily ski-specific questioaires have bee developed based o face to face ad iteret focus groups (IFGs) coducted i adults with oily ski i the Uited States ad Germay. The Oily Ski Self Assessmet Scale (OSSAS) is a measure of facial oily ski severity ad the Oily Ski Impact Scale (OSIS) assesses the emotioal impact of oily facial ski. The items were developed i both Germa ad Eglish because future trial ad istrumet validatio work was plaed for Germay. Coceptual frameworks were developed for both questioaires, guided by the qualitative focus group results. The draft questioaires were reviewed by dermatologists with expertise i quatitative ad qualitative oily ski assessmet measures (icludig the sixth ad seveth authors of the preset article), ad cogitive debriefig was coducted usig Iteret ad faceto-face methods. Revisios were the made to the items ad istructios. Details of the questioaire developmet process are provided elsewhere [8,13]. The qualitative research described above was coducted i adults aged 18 or older. However, followig these adult focus groups, further focus groups i adolescets were coducted for the purpose of assessig the face ad cotet validity of the OSSAS i the adolescet populatio. The study beig reported here ivolved admiisterig the OSSAS ad OSIS to 202 subjects i the Uited States, to perform item reductio ad evaluate the validity ad reliability of the fial istrumets , Pfizer, Ic /09/

2 Validatio of the OSSAS ad OSIS 829 Objective The objective of this study was to fialize the item-scale structures of the OSSAS ad OSIS ad evaluate the psychometric properties (validity ad reliability) of both questioaires. Methods Cross-Sectioal Validatio Study Desig This was a oradomized, cross-sectioal, validatio study, coducted at seve locatios across the Uited States ad ivolvig o study treatmet. Subjects with oily facial ski were recruited through advertisemets or if they were beig treated by oe of the recruitig cliicias. Subjects at two of the sites were asked to retur for a follow-up visit for the purpose of assessig test retest reliability. Subjects were erolled if they met the selectio criteria of the study, detailed below. Iclusio criteria. Subjects all cofirmed by self-assessmet that they had bothersome ( somewhat bothered ) oily facial ski ad had a desire to improve their oily ski. Subjects had to be willig to ot wear facial products at the time of a cliic visit ad willig ot to have started a ew treatmet for oily ski or ace withi 30 days precedig the first cliic visit. Subjects with o ace or mild to moderate ace were icluded i the sample. Presece ad severity of ace was determied by a ace lesio cout performed by the recruitig cliicia. All cliicias were traied i makig ace lesio couts by oe of the authors (R. Rizer) at the start of the study. Mild ace was defied as 2 to 10 iflammatory lesios ad o odules o the face: umber of o-iflammatory lesios ot limited. Moderate ace was defied as 11 to 40 iflammatory lesios ad o more tha oe small ( cm) odule o the face: umber of oiflammatory lesios ot limited. Noiflammatory lesios iclude ope ad closed comedoes, although iflammatory lesios iclude papules (elevatios of the ski ceterig o a sebaceous follicle), pustules (elevatios of the ski topped by pus), ad odules (larger elevatios of the ski). Exclusio criteria. Subjects were excluded if they had severe facial ace or ace such that it might iterfere with either the cliicia s or subject s assessmet of the oily ski. Subjects were excluded if they had facial hair, subur, or deep taig of the face (as assessed from visual ispectio by the cliicia). Subjects were also excluded if they were uwillig or uable to comply with the lifestyle guidelies. I additio to the iclusio ad exclusio criteria, the followig protocol-specific lifestyle guidelie activity restrictios applied to all study subjects. For 3 to 4 hours precedig the cliic visit, subjects were istructed ot to: 1. Make ay chages to their treatmet or daily ski care routie; 2. Expose their face to itese sulight or to itese UV rays as well as ay facial taig; 3. Wear ay facial products such as powders, moisturizers, or cosmetics; 4. Wash, clea, shave, blot, touch, or wipe their face; 5. Do ay exercise or aythig that might make their ski feel hot. The aim of these lifestyle guidelies was to reduce the variability of subjects oily ski because of exteral factors, ad to reduce the likelihood that perceived oily ski levels might be biased by factors other tha uderlyig sebum levels, e.g., because of sweat or cosmetic creams. At the baselie visit, the site ivestigator obtaied the subject s iformed coset ad completed a subject medical history. The ivestigator the esured that the subject met all of the iclusio ad exclusio criteria, icludig beig willig to comply with specific lifestyle guidelies. Next, the study ivestigator performed a ace lesio cout ad completed the Cliical Global Impressio of Severity (CGI-S); for subjects i the follow-up substudy, a sebumeter [14,15] assessmet was also performed. The subjects the completed the study PRO questioaires. I additio, the subjects also completed the Skidex-29 [16 18] ad the Ace-Specific Quality-of-Life (Ace-QoL) [19 21], two oily ski ad ace-specific quality of life measures, respectively, i order to validate the OSSAS ad OSIS agaist existig measures. At the ed of their first visit, subjects i the follow-up substudy were istructed to follow lifestyle guidelies withi 3 hours prior to their secod ad fial visit; this was to esure stadardized measuremets at both visits. The subset of subjects icluded i the follow-up substudy retured for a secod visit 7 days (+/- 3 days) after the baselie visit where they uderwet the same study procedures (sebumeter readig ad ace lesio cout) ad completed the PRO questioaires a secod time to allow assessmet of the test retest reliability of the istrumets. The ivestigator at each site esured that each subject was give full ad adequate oral ad writte iformatio about the ature, purpose, possible risks, ad beefits of the study. The study was coducted accordig to the priciples of the 1996 amedmet of the Declaratio of Helsiki ad approved by Copericus (a cetralized ethics committee i the Uited States). PRO Measures OSSAS. The OSSAS is a self-completed PRO measure of facial ski oiliess. The versio of the OSSAS icluded i this validatio study cosisted of a pool of 37 items [8]. OSIS. The versio of the OSIS i this validatio study icluded 14 self-completed items that assessed the impact of oily ski o emotioal well-beig [8]. Skidex-29. A assessmet of oily ski-specific symptoms, emotios, ad fuctioig were made usig the 7-day recall Skidex-29 [16 18]. The recall period of the Skidex-29 was adapted to 1 week after cosultatio with the developer, so that it was cosistet with the other istrumets icluded i the study. The item respose scales rage from ever to all the time o a five-poit Likert scale. Ace-QoL Questioaire. For subjects with ace, a assessmet of ace-specific symptoms, impact o self-perceptio, ad emotioal ad social fuctioig was made usig the Ace-QoL [19 21]. The Ace-QoL cotais 19 items ad asks subjects to recall over the past week. Resposes rage from ot at all to extremely or extesive to oe o a seve-poit Likert scale. Sigle-item self-assessmet questios. Subjects also completed three sigle-item self-assessmet questios, icluded i order to stratify subjects for kow group validity aalyses. The three items assessed subjects level of bother from their oily ski ( Overall, how bothered are you by your oily ski? ); the importace of improvig their oily ski appearace ( How importat

3 830 Arbuckle et al. is it to improve the appearace of your ski, specifically, the areas that are the most oily? ; ad their ratig of the level of ski oiliess ( How do you rate the level of your ski oiliess? ). Bother ad importace respose scales raged from ot at all to extremely o a five-poit Likert scale, ad levels of ski oiliess were categorized as oe, mild, moderate, ad severe. Subjects also completed a short, 16-item questioaire providig details about demographic ad cliical characteristics. Patiet Global Impressio (PGI). Subjects were asked to assess their facial oily ski severity o the most bothersome oily area of their face (as idetified by the OSSAS) usig a PGI of Severity (PGI-S) item developed for use i this study. Respose optios raged from 1 ( ot at all oily ) to 5 ( very severely oily ). At the secod visit, subjects i the follow-up substudy assessed the chage i the oily ski o the most bothersome area of their face sice the start of the study, usig a PGI of Chage (PGI-C) item, which was agai developed for use i this study. Possible respose optios were o a rage from 1 ( very much improved ) to 7 ( very much worse ). Cliical Measures Sebumeter. The Sebumeter SM815 (Courage-Khazaka Co., Cologe, Germay) [14,15] provides a direct measuremet of ski surface sebum i mg/cm 2. For subjects erolled i the follow-up substudy, the sebumeter was used to take measuremets of forehead sebum at both study visits. Ace lesio cout. For those subjects with ace, the study ivestigators performed a facial ace lesio cout to assess subjects facial ace severity [22]. All ivestigators received traiig i makig ace lesios couts prior to commecig the study. CGI. The ivestigators made a assessmet of the overall severity of the subject s facial oily ski usig the CGI-S. The CGI-S rated the severity of four areas of the face (forehead, ose, cheeks, ad chi) o a scale ragig from 1 ( ot at all oily ) to 5 ( very severely oily ). For subjects erolled i the follow-up substudy, at the secod visit, the study ivestigators assessed the chage i the subject s oily ski i the area of the face that was most bothersome to the subject sice the start of the study usig the CGI of Chage (CGI-C), with possible respose optios ragig from 1 ( very much improved ) to 7 ( very much worse ). The study ivestigators were also required to respod to a sigle questio askig about the overall health status of the subject, ratig the health of the subject as poor, fair, good, very good, or excellet. Item Reductio, Psychometric Validatio, ad Statistics A statistical aalysis pla for the study was writte ad fialized prior to commecemet of the study. Maximum likelihood factor aalysis was performed i order to assess the uderlyig structure of the OSSAS ad OSIS ad to idetify potetial items for item reductio. Factor aalysis was coducted separately for the OSSAS ad OSIS. Items were cosidered for deletio o the basis of a combiatio of face validity ad psychometric characteristics icludig: Failure to load o ay factor or loaded o more tha oe factor; a item-scale correlatio of <0.40; correlatig at a higher level with a scale other tha the item s hypothesized scale; >30% scorig at floor or ceilig; commets relatig to face validity give by participats i the adolescet focus groups; ad the importace ratigs give to the items by the participats i the IFGs [8]. Followig item reductio, the validity ad reliability of the fial item scale structures of the OSSAS ad OSIS were tested through further factor aalysis ad psychometric validatio aalyses. Costruct validity was evaluated through assessmet of item coverget validity (item-scale correlatio 0.40 were cosidered acceptable), item discrimiat validity (items should correlate more highly with the scale i which they are icluded tha ay other scale i the istrumet), ad floor ceilig effects (low percetages scorig at floor ad ceilig are recommeded) [23]. Both iteral cosistecy reliability (Crobach s alpha coefficiet should be >0.70) [24,25] ad test retest reliability (itraclass correlatio coefficiets for the total score ad each item >0.70 [26] for subjects who self-reported that their oily ski was uchaged betwee baselie ad visit 2 o the PGI-C at visit 2) were assessed. Cocurret validity assessmet ivolves examiig correlatios betwee the measure beig validated ad other wellvalidated measures of similar costructs [26]. Domais measurig similar costructs are expected to correlate highly whereas domais measurig very differet costructs should ot correlate. Here, correlatios of OSSAS ad OSIS domais with the domais of the Skidex-29 ad Ace-QoL were examied. Kow groups or discrimiative validity is the ability of a measure to distiguish amog groups that was expected to differ [27]. OSSAS ad OSIS scores were compared accordig to PGI-S categories, CGI-S categories, ad sigle-item self-assessmet questios bother categories, oiliess categories, ad the area of the face selected as the most bothersome. OSSAS ad OSIS groups scores were expected to differ at a statistically sigificat level amog the groups compared. For the OSSAS scores the primary aalysis was the compariso by the PGI-S categories. For the OSIS, the primary aalysis was the compariso by self-reported bother categories. The item reductio ad validatio aalyses were coducted usig data for the total cross-sectioal sample for all of the aalyses with the exceptio of the test retest aalyses which were coducted usig data oly from those subjects i the follow-up substudy. The Type-1 error was Pearso s correlatio coefficiet was used to evaluate the correlatio betwee the subscales. Group comparisos were performed usig aalysis of variace (three or more groups) or t test (two groups). Most of the aalyses were performed usig SAS versio (SAS Istitute, Ic., Cary, NC) for Widows; multitrait aalysis was performed usig Multitrait Multi-item Aalyses Program-Revised ruig o top of SAS versio 6.12 for Widows. Results The item reductio ad cross-sectioal psychometric validatio aalyses were performed o data from 196 subjects. A total of 152 subjects took part i the follow-up substudy for the purposes of assessig test retest reliability. A summary of the demographic ad cliical characteristics of this sample is preseted i Table 1. I the sample of 196 subjects icluded i the cross sectioal aalyses, 72% ( = 142) were female. Subjects were either experiecig mild ( = 19, 9.8%), moderate ( = 124, 63.9%) or severe oily ski ( = 45, 23.2%), i their ow opiio. There was missig data o this questio for eight (4%) subjects. Approximately two-thirds of subjects had ace (125, 64.4%) accordig to their ow self report. Sixty-five subjects self-rated their ace as mild, 55 self-rated their ace as moderate, ad 15 self-rated their

4 Validatio of the OSSAS ad OSIS 831 Table 1 Cross-sectioal validatio study baselie demographic ad cliical characteristics Characteristic Total sample (N = 196) Geder (%) Male 53 (27.2) Female 142 (72.8) Missig data 1 Age Mea (SD) 36.7 (12.14) Rage Ethicity White/Caucasia 119 (58.91) Africa America 24 (11.88) Hispaic/Spaish America 9 (4.46) Asia/Orietal or Pacific Islader 3 (1.49) Other 3 (1.49) Missig data 38 (19.38) Which is the most bothersome oily area of your face? (%) Forehead 81 (42.40) Nose area 80 (41.88) Chi 16 (8.38) Cheeks 14 (7.33) Missig data 5 O average, would you say that the oiliess of your ski is: (%) Mild 19 (9.8) Moderate 124 (63.9) Severe 45 (23.2) Missig data 8 (4) Do you have ace? (%) Yes 125 (64.4) No 56 (28.9) Missig data 15 (7.7) Curretly is your ace (%) Mild 65 (33.2) Moderate 55 (28.1) Severe 15 (8.7) Extreme 0 (0.0) Missig data 61 (31.1) ace as beig severe; oe of the subjects thought they had severe ace. Item Reductio of the OSSAS Followig the iitial data aalysis, a umber of items were deleted. Items were deleted because of: 1. beig itroductory items that became iappropriate because of a chage i the focus of the questioaire; the revised questioaire assesses the face as a whole rather tha oe selected area as i the origial versio; 2. havig poor face ad cotet validity, based o feedback from the adolescet focus groups; 3. havig poor psychometric properties; 4. ot beig relevat or importat for the measuremet of the cocept of oily ski. Followig item reductio, the coceptual framework for the OSSAS was revised. The fial OSSAS item-scale structure cosists of three multiitem domais that assess subjects oily facial ski through Visual (three items), Tactile (four items), ad Sesory (five items) methods (Fig. 1). A sigle blottig item was retaied but ot icluded as part of a domai score. I additio, based o the adolescet focus groups, it is recommeded that two additioal items be added: How greasy does your face feel? ad How oily is the ski o your face? It is aticipated that the greasy item will likely be icluded i the Sesatio scale ad that the item How oily is the ski o your face? will be scored as a sigle item as a measure of overall facial ski oiliess. Revisio of the respose optios to rate the ski o a scale of Not at all to Extremely o a0to10scale is also recommeded based o fidigs from the adolescet focus groups, which suggested that the origial respose optios were hard to uderstad. OSSAS Psychometric Validatio Costruct validity. Maximum likelihood factor aalysis was performed o the fial OSSAS items with the umber of factors fixed at four to reflect the four domais as hypothesized i the coceptual framework. Four items askig subjects to rate the sesatio of their oily facial ski (without lookig at or touchig their face) loaded o the first factor (factor loadigs ) ad were icluded i the Sesatio scale. The blottig item ad three items that ask about the feelig of oily ski to touch loaded o the secod factor (factor loadigs ), ad with the exceptio of the blottig item were icluded i the Tactile scale. The Blottig item was scored o its ow because it was felt to be measurig a distict cocept from a face validity perspective. Three items that pertai to the look of oily ski loaded o the third factor (factor loadigs ). A sigle item ( Overall, how oily does your ski look? ) loaded o the fourth factor o its ow (factor loadig 0.65) but was icluded i the Visual scale for reasos of face validity. The results demostrate that the OSSAS shows excellet scalig properties i this sample (Table 2). All of the items i each domai met the criteria for item coverget validity, correlatig with the other items i that domai (adjusted for overlap) at a level of >0.40. All items met the criteria for item discrimiat validity correlatig at a higher level with their ow domai tha ay other OSSAS domai. All correlatios amog the OSSAS domai scores were moderate (rage ), idicatig that the scales are measurig related but ot redudat cocepts (Table 2). There were o sigificat floor or ceilig effects ad, oe of the scales had overly skewed respose distributios. Reliability. The Sesatio, Visual, ad Tactile scales had Crobach s alpha coefficiets of 0.86, 0.83 ad 0.89, respectively (Table 2), idicatig excellet iteral cosistecy reliability. The threshold for acceptable test retest reliability (ICC 0.70) [24] was met by the OSSAS Sesatio scale (ICC = 0.71) but ot by the Visual (ICC = 0.64) ad Tactile (ICC = 0.63) scales or the Blottig item (ICC = 0.62) (Table 2). Cocurret validity. The cocurret validity of the OSSAS was assessed by examiig correlatios of its domais with those of the Skidex-29 ad Ace-QoL. All correlatios betwee the OSSAS ad Skidex-29 domais could be cosidered small, ragig from 0.20 to However, this is usurprisig as the OSSAS is focused o oily ski symptoms whereas the Skidex-29 assesses symptoms, emotios, ad fuctioig related to ski coditios. Correlatios betwee the OSSAS ad Ace-QoL domais were all small or egligible, ragig from to Agai, this fits with expectatios give that the two istrumets are measurig very differet cocepts. Kow groups validity. The primary test of kow group validity was the compariso of OSSAS scores by subject report of oily ski severity as rated by the PGI-S. Because of small sample sizes,

5 832 Arbuckle et al. 16. How shiy is your ski? 19. How moist does the ski surface look? 24. Overall, how oily does your ski look? Visual 35. How oily is the blottig paper? Blottig 26. How slippery is your ski whe stroked? 31. How sticky is your ski whe touched? 28. How oily do your figers feel after strokig your ski? 33. Overall, how oily does your ski seem whe stroked? Tactile Facial Oily Ski Severity How oily is the ski o your face?* 13. Overall how ucomfortable does your ski feel? 11. How heavy does your ski feel? 8. How uclea does your ski feel? 14. Overall, without touchig or lookig at your ski, how oily does your ski feel? How greasy does your face feel?* Sesatios * New items added to the OSSAS durig the item reductio process Figure 1 OSSAS coceptual framework. some of the PGI-S levels were collapsed together i the aalysis, thus comparisos were made amog the three groups: Not at all/mildly oily ( = 18), Moderately oily ( = 104), ad Severely/ Very Severely oily ( = 61). For all of the OSSAS scales, there were statistically sigificat differeces amog the three collapsed oily ski severity groups (P < ) (Table 3). I additio, for all of the OSSAS scales (Sesatio, Visual, ad Tactile) ad the Blottig item, subjects who reported havig Severely/very severely oily ski had higher (i.e., worse) OSSAS scores tha subjects who reported havig moderate, mild, or o oily ski (Table 3). However, cotrary to expectatios, subjects who reported havig Not at all/mildly oily ski also had slightly worse (higher) OSSAS scores tha subjects i the Moderately oily group. These results should be iterpreted with cautio because of the small sample size of the Not at all/ Mildly group ( = 18). For the comparisos of OSSAS scale scores by cliicia-rated oiliess ad subject-rated bother, the expected patters of higher (worse) OSSAS scores for worse cliicia-rated oily ski ad worse subject rated-bother were obtaied with statistically sigificat differeces amog the groups (P < ; Table 3). Fially, Pearso s correlatios betwee OSSAS scores ad their averaged sebumeter scores were examied at visit 1. The sebumeter scores ad the Sesatio scale scores failed to correlate (r = 0.01), although the correlatios betwee the sebumeter ad the OSSAS Visual, Tactile, ad Blottig scores were all i the low rage (r = 0.22, r = 0.32, ad r = 0.34, respectively), suggestig there is oly a limited relatioship. Item Reductio of the OSIS Eight items were deleted from the OSIS. Items were deleted because of redudacy with other items (five items), poor face validity (oe item), because of askig about more tha oe cocept i the same item (two items), or presece of a sigificat floor effect (oe item). Based o the adolescet focus group feedback, the OSIS respose cotiuum was revised from a five-poit scale ragig from Never to Very ofte to a 10-poit scale ragig from Not at all to Extremely. Followig item reductio, the coceptual framework of the OSIS was revised; the fial OSIS coceptual framework is provided i Figure 2. OSIS Psychometric Validatio Costruct validity. Table 4 outlies the results of the maximum likelihood factor aalysis, which was performed o the fial

6 Validatio of the OSSAS ad OSIS 833 Table 2 OSSAS costruct validity, floor ad ceilig, ad reliability results Costruct validity Floor ad ceilig effects* Reliability Item coverget validity Item discrimiat validity Iteral cosistecy reliability Test retest reliability (Itraclass correlatios) Correlatio rage Success rate (%) Success rate (%) % at floor % at ceilig Crobach s alpha PGI-C CGI-C # Scale No. of items Factor loadigs Sesatio Visual Tactile Blottig ** N/A N/A N/A N/A *<20% scorig at floor or ceilig was cosidered acceptable. ICC computed usig Shrout Fleiss reliability: sigle score statistic. Dataset icludes Visit 1 ad Follow-up Visit 4 visits. Item-dimesio correlatios Percetage of item-dimesio correlatios that were higher with the item s ow dimesio tha with the other dimesios. Acceptable if Crobach s alpha was Stable subject defied as those subjects who report No chage o the Patiet Global Impressio of Chage (PGI-C) item. # Stable subject defied as havig No chage i their coditio o Cliical Global Impressio of Chage (CGI-C) item. **Actor loadig with the Tactile scale. N/A, ot applicable. OSIS items to establish the scorig of the istrumet. All items performed well, loadig at a level of >0.30 with oe factor. Three items askig about the aoyace/irritability of oily ski loaded most highly o the first factor (factor coefficiets of 0.77, 0.73 ad 0.57, respectively) ad were icluded o the Aoyace scale. The three remaiig items loaded most highly o the secod factor (coefficiets of 0.84, 0.75 ad 0.52, respectively) ad were icluded i the Self-Image scale. All items met the criterio for item coverget validity (itemscale correlatios >0.40), with item scale correlatios ragig from 0.60 to 0.78 (Table 4). All items were foud to correlate more highly with their ow scale tha with the other OSIS scale thus the criterio for item discrimiat validity was satisfied. The correlatio betwee the two scales of the OSIS was moderate (r = 0.75), suggestig that the scales are measurig cocepts that are related but ot redudat (Table 4). The percetages of subjects scorig at floor (lowest possible score) ad ceilig (highest possible score) were low for both of the scales ad so were acceptable. Reliability. The iteral cosistecy reliability results for the OSIS were excellet, with Crobach s alpha coefficiets of 0.87 for the Self-Image scale ad 0.82 for the Aoyace scale (Table 4). Defiig stable subjects as those who reported o chage o the PGI, the stadard for acceptable test retest reliability (ICC 0.70) [24] was surpassed by the Aoyace scale (ICC = 0.74) but the result for the Self-Image scale fell just below the a priori threshold (ICC = 0.69). Cocurret validity. Correlatios betwee OSIS scores ad Skidex-29 scores raged from r = 0.37 to r = Both the OSIS Self-Image ad Aoyace scales correlatig most highly with the Skidex-29 Emotios scale (r = 0.69 ad r = 0.73). Correlatios with the Ace-QoL raged from r =-0.48 to r =-0.73, with the OSIS Self-Image scale correlatig most highly with the Self-Perceptio scale (r =-0.67) ad the OSIS Aoyace scale correlatig at the highest level with the Role-emotioal scale (r =-0.73). These results make sese whe cosiderig the cotet of the scales. Kow groups validity. Kow group validity results for the OSIS are preseted i Table 5. For both scales, there was a clear patter of higher OSIS scores (idicated greater emotioal impact of oily ski) for subjects who reported beig more bothered by their oily ski (P < ). OSIS scores were also compared accordig to subjects selfreported oily ski severity o the PGI-S (Table 5). Subjects who rated their facial ski as more oily o the PGI-S scored worse o the OSIS Aoyace scale (P < 0.001). For the Self-Image scale, although there were statistically sigificat differeces amog the three groups (P < 0.001), the expected patter of results was ot foud subjects who rated their ski as Moderately oily scored better o the Self-Image scale tha subjects who rated their ski as Not at all/mildly oily. However, the results should be iterpreted with cautio because of the small sample size ( = 18) of the Mildly/Not at all oily group. Discussio Whe patiets preset to dermatologists with a complait of oily ski, the cliicia geerally relies o the patiet s report regardig the severity ad impact of the coditio. The use of PRO measures such as the OSSAS ad OSIS is oe way to attempt to

7 834 Arbuckle et al. Table 3 OSSAS kow groups aalyses OSSAS domai score Sesatio Visual Tactile Blottig Mea (SD) Mea (SD) Mea (SD) Mea (SD) Patiet Global Impressio of Severity (PGI-S)* Not at all/mildly 58.1 (19.94) 61.9 (16.62) 64.1 (17.88) 3.4 (1.38) Moderately 56.3 (14.14) 60.3 (11.14) 60.5 (12.58) 3.2 (0.83) Severely/Very severely 69.8 (14.96) 71.2 (15.98) 74.8 (15.01) 4.1 (0.83) P value (ANOVA) < < < < Subject self-assessmet of ski oiliess Mild 50.7 (11.24) 57.2 (8.82) 56.1 (10.77) 3.0 (0.96) Moderate 61.2 (15.55) 63.4 (14.03) 65.4 (14.23) 3.4 (0.96) Severe 73.8 (17.41) 72.9 (14.84) 79.3 (2.88) 4.3 (0.75) P value (ANOVA) < < < < Subject self-assessmet of bother Somewhat bothered 53.5 (14.12) 58.9 (11.29) 59.1 (13.79) 3.0 (0.92) Very bothered 65.8 (14.31) 66.6 (13.24) 69.7 (13.04) 3.8 (0.88) Extremely bothered 72.1 (21.49) 70.2 (21.59) 76.1 (19.54) 4.1 (1.03) P value (ANOVA) < < < < CGI-S ose area Mildly 53.3 (10.33) 57.8 (13.11) 56.7 (13.82) 3.0 (1.67) Moderately 58.5 (14.91) 60.7 (11.72) 61.5 (13.95) 3.4 (0.85) Severely 65.7 (16.22) 71.0 (15.93) 73.0 (14.98) 3.7 (0.90) P value (ANOVA) CGI-S forehead area Mildly 60.5 (14.91) 55.2 (10.37) 58.2 (13.36) 3.0 (1.00) Moderately 59.7 (16.80) 65.0 (11.24) 65.3 (12.92) 3.5 (0.85) Severely 62.9 (16.93) 65.6 (17.98) 69.7 (16.68) 4.0 (1.14) Very severely 74.5 (17.10) 73.9 (18.96) 80.6 (15.62) 4.1 (0.94) P value (ANOVA) Correlatio with sebumeter assessmet *As defied by the PGI-S assessmet (subjects rate their ow level of ski oiliess o a 5-poit scale ragig from Not at all oily to Very Severely Oily ). Subject rates level of ski oiliess o a scale of mild, moderate, ad severe. No defiitios for the categories were provided; this was left to patiet iterpretatio. Subjects rate how bothered they are by their oily ski o a 5-poit scale ragig from Not at all bothered to Extremely bothered. Cliicia ratig of the severity of ski oiliess i a particular area o a 5-poit scale from Not at all oily to Extremely oily. ANOVA, aalysis of variace; CGI-S, Cliical Global Impressio of Severity. stadardize patiets reports of their coditio, allowig for valid ad reliable measuremet i large studies such as cliical trials. The study reported here provides iitial evidece of strog validity ad iteral cosistecy for the OSSAS ad OSIS i this sample of adults with oily facial ski. Followig item reductio, psychometric validatio of the OSSAS suggests that the three hypothesized multiitem scales ad the sigle blottig item have strog costruct validity. Factor aalysis results were strog with almost all items loadig o factors correspodig to the domais i which they were icluded, ad oe of the items loaded o more tha oe factor. Multitrait aalysis showed that all items also correlated with the domais i which they were icluded ad all three multiitem scales showed high iteral cosistecy. Of some cocer, the a priori threshold for test retest reliability was oly met by the Sesatio scale although the Tactile ad Visual domais ad Blottig item were all approachig this threshold ad should ot be cosidered poor. The reasos for these test retest reliability results are uclear oe possibility is that the subjects oily ski was more variable tha predicted, ad results could possibly be improved by shorteig the timeframe betwee first ad secod visits for this assessmet. It is hoped that proposed chages to the istructios ad format of the OSSAS may lead to improvemets i test retest reliability; further testig of test retest reliability is required to verify this. Correlatios of the OSSAS domais with those of the Skidex-29 ad Ace-QoL were all small, but this makes sese give that these measures are all assessig quite differet cocepts. Other similar measures to the OSSAS which might have provided better results for cocurret validity were ot available at the time of this study [9]. I geeral, the discrimiative or kow groups validity results suggest the OSSAS is able to discrimiate amog kow groups. The expected patter of results was achieved for four of the five discrimiative validity criteria evaluated. Oly the compariso of scores for subject ratig of severity did ot yield the expected patter, but this may

8 Validatio of the OSSAS ad OSIS 835 Over the past week, how much did the oiliess of your face make you feel: 3. Frustrated 4. Aoyed 5. Irritated Aoyace Impact of Oily Ski Symptoms Over the past week, how much did the oiliess of your face make you feel : 1. Uattractive 2.Embarrassed 6. Self-coscious Self image/self cocept Figure 2 OSIS coceptual framework. be because of collapsig the groups or the small sample size of the Not at all/mildly oily group ( = 18). Further testig of discrimiative validity i a larger sample is recommeded i future studies. All of the OSSAS scales had low correlatios with the sebumeter. As the validity of the sebumeter has ot bee demostrated, it is difficult to iterpret this result. It may idicate that the PRO ratig is partly affected by psychological issues as well as the objective level of oiliess. Arguably, the low correlatios idicate that it is importat to iclude both cliical ad patietreported measures of facial oiliess as ed poits i ay study. Aalyses suggested that both OSIS domai scores have strog psychometric properties. All OSIS items performed well i the factor aalysis with oly oe item askig about Selfcosciousess loadig o two factors. However, the item loaded most highly o the Self-Image factor, o which it was ultimately placed; therefore, this result is ot of cocer. All items met the criterio for both item coverget validity ad item discrimiat validity ad results for iteral cosistecy reliability were excellet, with Crobach s alpha coefficiets well above the recommeded threshold (0.70) for both scales. A result of slight cocer for the OSIS was the test retest reliability of the Self- Image scale, which fell margially below the threshold of 0.70 for acceptability. The correlatios of the OSIS domais with the Skidex-29 ad Ace-QoL made sese i terms of the face validity of the scales (scales measurig similar cocepts correlated highly, correlatios amog other scales were small), thus providig evidece of satisfactory cocurret validity. The OSIS also showed the ability to discrimiate betwee groups that would be expected to differ. Whe the OSIS scale scores were compared by self assessmet of ski oiliess, CGI-S scores ad subject report of bothersomeess of their oily ski, the expected patter of results was see for the Aoyace scale i all cases, ad for three out of the five assessmets for the Self-Image scale. I both cases where the expected patter of results was ot see (PGI-S ratig ad CGI-S forehead), there were very small sample sizes, ad so the results should be iterpreted with cautio. The low correlatios betwee the OSIS ad sebumeter are usurprisig, give that the sebumeter measuremet is take at the poit of the cliic visit, where the OSIS asks the subject to thik back over the past week. Psychometric validatio was performed o data collected from male ad female adult participats who had a rage of oiliess severity levels from mild to severe ad some of who had ace i additio to their oily ski. Thus, evidece has bee preseted to suggest that the istrumets are appropriate for use i adults with differig levels of oily ski severity ad with or without ace. I recet moths, the Oily Ski Self-Image Questioaire (OSSIQ), developed i Frech for use i wome with oily ski, has bee published [9]. Although also beig specific to oily ski, the OSSIQ has quite a differet focus compared to both the OSSAS ad OSIS. It icludes cotet most closely related to the cocepts measured by the OSIS (Self-Image ad Aoyace), but focuses o more depressive ad axious feeligs arisig from oily ski (e.g., my ski makes me feel depressed ad my ski problem is stressful ), with oly a few items askig about Self- Image, ad oe askig about Aoyace related to oily ski. I additio, it should be oted that the OSSIQ is cocered with oily ski i geeral, whereas the OSSAS ad OSIS are focused o oly oily facial ski. Thus, the istrumets could be cosidered to be complemetary rather tha redudat: Where a measure of the experiece ad severity of oily facial ski is required, the OSSAS might be the most appropriate istrumet; if a assessmet of the psychosocial impact of oily ski i geeral is required, use of the OSSIQ might be appropriate; if a measure of self image ad aoyace related to facial oily ski is of iterest, the the OSIS might be preferred. Limitatios ad Further Research This study was performed i a sample of ative Eglish speakers i the Uited States; it would be ecessary for further validatio to be performed i other laguages ad cultures to cofirm the cross-cultural validity of the istrumet. A further limitatio was the absece of a well-validated cliical measure agaist which the PRO scores could be compared for cliical validity. Thus far, the sebumeter, agaist which the measures were assessed, has oly limited evidece of validity [28] ad therefore results should be iterpreted with cautio. I this study, subjects were asked to follow a umber of lifestyle guidelies, i order to reduce variability i their oily ski ratig because of covariates such as sweatig as a result of

9 836 Arbuckle et al. Table 4 OSIS costruct validity Costruct validity Floor ad ceilig effects* Reliability Item coverget validity Item Discrimiat validity Iteral cosistecy reliability Test retest reliability (itraclass correlatios) Correlatio rage Success rate (%) Success rate (%) % at floor % at ceilig Crobach s alpha PGI-C CGI-C # Scale No. of Items Factor loadigs Self-Image Aoyace *<20% scorig at floor or ceilig was cosidered acceptable. ICC computed usig Shrout Fleiss reliability: sigle score statistic. Dataset icludes Visit 1 ad Follow-up Visit 4 visits. Item-dimesio correlatios Percetage of item-dimesio correlatios that were higher with the item s ow dimesio tha with the other dimesios. Acceptable if Crobach s alpha was Stable subject defied as those subjects who report No chage o the Patiet Global Impressio of Chage item. # Stable subject defied as havig No chage i their coditio o Cliical Global Impressio of Chage item. Table 5 physical exertio or variatios i lightig coditios. It is aticipated that similar guidelies would be followed i ay cliical trials that might use the istrumets as ed poits, i order to esure ay chages i scores are because of true chages i oily ski severity, rather tha chages i evirometal coditios or other covariates. However, the validity fidigs reported here might ot geeralize to situatios i which it is ot feasible to cotrol these covariates, such as geeral cliical practice. I such istaces, further validatio might be recommeded through a study that employs a more aturalistic study desig i which these variables are ot cotrolled. Resposiveess ad miimal importat differeces have ot yet bee examied for the OSSAS ad OSIS. These properties could ot be assessed i this validatio study as subjects received o treatmet ad therefore were ot expected to experiece a chage i their oily ski. Followig commets give by the adolescet subjects ad discussios durig item reductio, the focus of the OSSAS was chaged from assessig the most bothersome area of the face to the assessmet of the whole face. Additioally, the respose optios of both measures were chaged from five-poit Likert scales to achored, 0 to 10 umerical ratig scales. Further cogitive debriefig to test face ad cotet validity of the istrumets with these revisios is recommeded to esure items are still comprehesible ad acceptable to both adults ad adolescets. Coclusios OSIS kow groups aalyses OSIS domai scores Self-Image Aoyace Mea (SD) Mea (SD) Subject self-assessmet of bother* Somewhat bothered 50.3 (17.48) 44.1 (16.93) Very bothered 66.9 (17.96) 61.2 (17.41) Extremely bothered 77.9 (23.31) 78.9 (16.22) P value (ANOVA) < < Patiet Global Impressio Severity (PGI-S) Not at all/mildly oily 59.6 (25.31) 51.5 (22.50) Moderately Oily 57.6 (19.04) 52.1 (18.95) Severely/Very severely oily 71.3 (18.32) 67.6 (17.99) P value (ANOVA) < < Subject self-assessmet of ski oiliess Mild 51.0 (19.05) 46.4 (18.81) Moderate 61.0 (20.12) 55.4 (18.81) Severe 73.6 (18.64) 68.6 (17.86) P value (ANOVA) < < *Subjects rate how bothered they are by their oily ski o a 5-poit scale ragig from Not at all bothered to Extremely bothered. As defied by the PGI-S assessmet (subjects rate their ow level of ski oiliess o a 5-poit scale ragig from Not at all oily to Very Severely Oily ). Subject rates level of ski oiliess o a scale of mild, moderate, ad severe. No defiitios for the categories were provided; this was left to patiet iterpretatio. ANOVA, aalysis of variace. The versios of the OSSAS ad OSIS tested i this study have bee show to have strog psychometric properties i this

10 Validatio of the OSSAS ad OSIS 837 sample of adults with self-reported oily facial ski. Results suggest they provide valid measures of self-reported oily facial ski severity ad its emotioal impact, respectively. Further testig is required to defie miimal importat differeces for the istrumets ad esure they have the ability to detect chage i facial oil over time. The authors would like to ackowledge the sigificat cotributio of Kathlee Rosa i writig the statistical aalysis pla. Lida Abetz helped with iterpretatio of results. Richard McLai ad Cathie Spio were also ivolved i the item reductio meetig ad the iterpretatio of the statistical aalysis results. The authors would also like to thak Dr. Da Clarke, Dr. Gregario Tamboe, Dr. Barbara Goldstei, Dr. K. Neea Chima, ad Dr. Elea Kadel for recruitig the subjects, performig ace lesio couts, ad admiisterig the questioaires. Fially, they would like to thak the subjects who participated i the study. RA, MC, JH, JS, ad KC coceived of ad desiged the study. For the psychometric validatio study, RA, MC, JH, JS, KC, ad NB wrote the protocol ad reviewed ad provided iput o the statistical aalysis pla. RR traied the other ivestigators i performig the ace lesio couts. RR ad ZD reviewed the protocol, recruited the subjects for the substudy, ad performed the sebumeter readigs ad ace lesio couts for the majority of subjects. RA ad NB maaged the collectio of the data. YY performed the statistical aalysis. RA, MC, JH, JS, KC, NB, ad YY participated i the item reductio meetig ad the iterpretatio of the results. RA ad NB wrote up all of the results ad wrote the first draft of the article. All authors reviewed the mauscript ad provided iput. Source of fiacial support: This study was supported by Pfizer. Marci Clark, Kati Copley-Merrima, ad Jae Haress were employees of Pfizer whe the project was performed. All other authors were cotracted by Pfizer as cosultats to work o this project. Supportig iformatio for this article ca be foud at: Refereces 1 Eblig FJ, Rook A. The sebaceous glad. I: Rook A, Wilkiso DS, Eblig FJ, eds. Textbook of Dermatology (3rd ed.). Oxford: Blackwell Scietific, Burto JL, Pye PJ. Seborrhoea is ot a feature of seborrhoeic dermatitis. Br Med J 1983;286: Seborrhea. I: Igeix, Hopkis CA, eds. ICD-9-CM Professioal for Physicias 2005, Vol 1& 2. New York: Thomso Delmar Learig, 2004: Thiboutot D. Regulatio of huma sebaceous glads. J Ivest Dermatol 2004;123: Nguye QH, Kim YA, Schwartz RA. Maagemet of ace vulgaris. Am Fam Physicia 2004;50: Draelos ZD, Matsubara A, Smiles K. The effect of 2% iaciamide o facial sebum productio. J Cosmet Laser Ther 2006;8: Draelos ZD. The effect of a daily facial cleaser for ormal to oily ski o the ski barrier of subjects with ace. Cutis 2006;78: Arbuckle R, Atkiso MJ, Clark M, et al. Patiet experieces with oily ski: the qualitative developmet of cotet for two ew patiet reported outcomes questioaires. 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Psychometric cosideratios i evaluatig health-related quality of life measures. Qual Life Res 1993;2: Hays RD, Aderso R, Revicki D. Assessig Reliability ad Validity of Measuremet i Cliical Trials. Quality of Life Assessmet i Cliical Trials: Methods ad Practice. Oxford, UK: Oxford Uiversity Press, Bertolio AP, Burey K, Haress J. A methodology study to evaluate ski oiliess, ski shie ad fuctioal parameters of Meibomia ad Adreal Glads Mar 8. Report No.: Pfizer Cliical Study Report A