Validation of Self-testing as a Method to Estimate the Prevalence of Nickel Allergy

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1 Vlidtion of Self-testing s Method to Estimte the Prevlence of Nickel Allergy Josefson, Ann; Svensson, Ake; Frm, Gunill; Engfeldt, Mlin; Meding, Birgitt Published in: Act Dermto-Venereologic DOI: / Published: Link to publiction Cittion for published version (APA): Josefson, A., Svensson, A., Frm, G., Engfeldt, M., & Meding, B. (2011). Vlidtion of Self-testing s Method to Estimte the Prevlence of Nickel Allergy. Act Dermto-Venereologic, 91(5), DOI: / Generl rights Copyright nd morl rights for the publictions mde ccessible in the public portl re retined by the uthors nd/or other copyright owners nd it is condition of ccessing publictions tht users recognise nd bide by the legl requirements ssocited with these rights. Users my downlod nd print one copy of ny publiction from the public portl for the purpose of privte study or reserch. You my not further distribute the mteril or use it for ny profit-mking ctivity or commercil gin You my freely distribute the URL identifying the publiction in the public portl Tke down policy If you believe tht this document breches copyright plese contct us providing detils, nd we will remove ccess to the work immeditely nd investigte your clim. L UNDUNI VERS I TY PO Box L und Downlod dte: 17. Oct. 2018

2 Act Derm Venereol 2011; 91: INVESTIGATIVE REPORT Vlidtion of Self-testing s Method to Estimte the Prevlence of Nickel Allergy Ann Josefson 1, Åke Svensson 2, Gunill Färm 3, Mlin Engfeldt 4 nd Birgitt Meding 5 Deprtments of Dermtology, 1 Örebro University Hospitl, School of Helth nd Medicine, Örebro University, 2 Skåne University Hospitl, Mlmö, Lund University, 3 Krolinsk University Hospitl, Stockholm, 4 Deprtment of Occuptionl nd Environmentl Dermtology, Skåne University Hospitl, Lund University, Mlmö, nd 5 Institute of Environmentl Medicine, Krolinsk Institutet, Stockholm, Sweden The im of this study ws to investigte the vlidity of self-ptch testing for nickel llergy, in order to determine cost-effective method for surveillnce of the prevlence of nickel llergy. Popultion-bsed study including ptch testing is the most relible method to study the prevlence of llergy, but it is expensive nd hs logisticl problems. A totl of 191 dermtology ptients referred to ptch testing were provided with self-test pckge with written instructions. The self-test ws pplied on the rm by the ptient, on the sme dy tht the regulr ptch test ws pplied on the bck. The ptient evluted the self-test before ptch test reding t the clinic. Ptch test t the dermtology clinic detected 46/191 (24%) nickel-positive individuls. The sensitivity of the self-test ws 72% (95% confidence intervl (CI) 57 84), the specificity 91% (95% CI 85 95), nd the proportion of greement 86% (95% CI 81 91). Thus, in the popultion studied, the vlidity of self-testing for nickel llergy ws dequte. Key words: contct llergy; epidemiology; ptch test; self-test; sensitivity; specificity. (Accepted Jnury 24, 2011.) Act Derm Venereol 2011; 91: Ann Josefson, Deprtment of Dermtology, Örebro University Hospitl, SE Örebro, Sweden. E-mil: nn.josefson@orebroll.se Contct llergy is common. Popultion-bsed studies show tht the prevlence of contct llergy is pproximtely 20% mong dult Scndinvins (1 4). Among dolescents in Denmrk, Mortz et l. (5) found tht the prevlence of contct llergy ws 15%. The most prevlent llergens re nickel, frgrnces nd preservtives. Nickel llergy is more common in women thn in menin ll previous studies. Most studies on nickel llergy re mde in western Europe nd in Scndinvi. The prevlences mentioned (1) re from rewiew of popultion-bsed dt pst decdes. Allergic contct dermtitis is recognized s public helth problem nd prevention is of importnce (6). Legisltion my be effective in preventing contct llergy, nd the Europen Nickel Directive (7) cme into full force in The directive limits permissible nickel relese from items in prolonged contct with the skin, e.g. jewellery, wtches, buttons nd zips (8). Continuous epidemiologicl surveillnce is necessry to determine the prevlence of contct llergy nd to evlute interventions. Thus, relible nd inexpensive epidemiologicl tools re required. Genuine popultion studies including ptch tests re difficult to perform for logisticl resons. Dt from ptch tests t the clinic re sometimes used to estimte the prevlence of contct llergy. However, such dt comprise selected mteril nd re not representtive of the generl popultion. Regrding nickel llergy in the generl popultion, it ws found in previous study tht 56% of subjects with nickel llergy hd no self-reported symptoms of dermtitis (9). For epidemiologicl surveillnce of common skin diseses in the generl popultion, questionnires my be useful, provided tht the questions re vlidted. Questions bout self-reported nickel llergy hve been vlidted in few studies (9 12). The vlidity of selfreported nickel llergy ws low in ll the studies, hving positive predictive vlue of 31 58%. Consequently, the questions overestimte the true prevlence. To investigte the prevlence of nickel llergy other methods re necessry. A self-test kit, Nixem (Mekos Lbortories ApS, Hillerød, Denmrk), hs recently been introduced on the Swedish mrket for detection of contct llergy to nickel nd frgrnce llergy. Self-testing might be useful method to investigte the prevlence of contct llergy in the generl popultion, but the method hs to be vlidted nd evluted. The im of the present study ws to compre results from self-ptch testing, performed nd red by the ptient, with results from ptch testing using n estblished method, performed nd red by the dermtologist. METHODS Study popultion The study ws performed t three dermtology deprtments, Örebro University Hospitl, Krolinsk University Hospitl Soln nd Skåne University Hospitl. Ptients were included consecutively from the clinics when referred to ptch testing s prt of the clinicl investigtion. Inclusion criteri were: 2011 The Authors. doi: / Journl Compiltion 2011 Act Dermto-Venereologic. ISSN

3 Vlidtion of self-testing for nickel llergy prevlence 527 Tble I. Chrcteristics of the prticipnts (n = 191) Chrcteristics Örebro/Soln/Skåne, n 94/27/70 Women, n (%) 132/191 (69) Men ge, yers (rnge) 44 (18 65) History of topic dermtitis, n (%) 82/185 (44) Resons for ptch test, n (%) Hnd eczem 76/191 (40) Fcil eczem 39/191 (20) Eczem on lower legs 9/191 (5) Other eczem 60/191 (31) Other reson 28/191 (15) Multiple lterntives possible. ge yers; nd ble to red nd understnd Swedish. Exclusion criteri were: previous ptch test; systemic tretment with corticosteroids; ntihistmine or other immunosuppressive tretment; exposure to ultrviolet (UV) light or topicl tretment with corticosteroids on the test re during the pst 14 dys; pregnncy; nd dermtitis on the test re. In totl, 191 ptients prticipted, 69% women, nd the men ge ws 44 yers (Tble I). Ptient s history of topic dermtitis ws obtined from their medicl records. Ptch testing The ptients were referred to ptch testing s prt of n investigtion of eczem. They were tested with nickel sulphte 5% pet. nd frgrnce mix 8% pet. (cinnmic lcohol, cinnmic ldehyde, hydroxycitronelll, mylcinnmldehyde, gerniol, eugenol, isoeugenol, nd okmoss bsolute, ll 1%) included in the Swedish bseline series provided by Chemotechnique Dignostics, Vellinge, Sweden. Allergens were pplied on Finn chmbers on Scnpor tpe (Epitest Ltd Oy, Tuusul, Finlnd) or on IQ Ultr Chmbers (Chemotechnique Dignostics) nd fixed to the ptient s bck with dhesive tpe, Fixomull or Scnpor. Ptch tests were pplied for 2 dys on the bck, nd redings were performed on dy (D)3 4 nd D7. The redings were performed by different dermtologists s prt of routine clinicl investigtions. Morphologicl evlution ws performed ccording to interntionl stndrd, Interntionl Contct Dermtitis Reserch Group (ICDRG) (13). For the nlysis of dt, +, ++, nd +++ redings were pooled s positive ptch tests. Positive ptch testing to nickel sulphte D3 nd/or positive ptch testing on D7 re referred to s positive by the gold stndrd. Self-testing Ptients included in the present study received self-test pckge on the sme dy s the ptch test ws pplied on the bck. The self-test used in the study, Nixem (Mekos Lbortories ApS, Hillerød, Denmrk), ws purchsed t the hospitl phrmcy. The self-test is medicl plster tht incorportes two llergen ptches with nickel sulphte, 0.16 mg/ptch, nd frgrnce mix, 0.35 mg/ptch, respectively. The frgrnce mix contins the sme substnces s the ptch test used on the bck. The technique nd test substnces in Nixem self-test re identicl to those used in Mekostest (former TRUE test) (Mekos Lbortories ApS, Hillerød, Denmrk) (14, 15). The Nixem test pckge contined detiled written stndrd instructions from the supplier s to how to pply the test on the upper rm nd how to evlute the result. The ptients pplied the self-test on the upper rm on the sme dy s the ptch test ws pplied on the bck. The self-reding ws crried out by the ptient on D3 4, before the ppointment t the clinic. The ptient evluted by scoring positive or negtive on recording sheet, which ws delivered to the investigtor in seled envelope tht ws not opened until nlysis. The dermtologist then red the ptch test on both the bck nd the rm. Sttisticl nlysis The dt were nlysed using SPSS version 15 (SPSS Inc., Chicgo, IL, USA). Sensitivity, specificity, negtive/positive predictive vlues nd proportion of greement were clculted using the ptch test results on the bck, red by the dermtologist s gold stndrd. These proportions were supplemented with 95% confidence intervls (95% CI) using binominl distribution nd clculted with STATA version 10 softwre (College Sttion, TX, USA). A χ 2 test ws used for comprison of proportions. The study ws pproved by the ethics committee of Uppsl, Sweden (2009/059). RESULTS Nickel llergy Ptch test s gold stndrd detected 24% nickelpositive individuls (Örebro 24%, Soln 19%, Skåne 26%). Forty-one women nd five men were positive to nickel in the ptch test. In ddition, three doubtful (IR or +?) rections were found. Self-test results red by the ptients compred with the estblished ptch test method red by dermtologists re shown in Tble II. Forty-six individuls evluted the self-test s positive for nickel nd 33 of those were regrded s positive by the gold stndrd. Another 13 individuls evluted the self-test s negtive for nickel, even though it ws positive by the gold stndrd. Ptch test results red by the dermtologist t D3 4, t D7, nd the conclusion from both occsions ( gold stndrd ) re presented in Tble II. The result fter one reding t D3 4 on the Tble II. Self-test results red by the ptient in reltion to ptch test results red by the dermtologist Nickel ptch test (dermtologist s reding, bck), n Reding D3 4 Reding D7 Gold stndrd Totl, n Positive b Negtive Positive b Negtive Positive b Negtive Self-test (ptient s reding, rm) Positive Negtive Gold stndrd is the conclusion from ptch test reding by dermtologist on dys 3 or 4 (D3 4) nd dy 7 (D7) combined. b Rections clssed s +, ++, or +++ re ll regrded s positive.

4 528 A. Josefson et l. Tble III. Clculted vlidity of the self-test in reltion to dermtologist s reding D 3 4 nd gold stndrd bck gve 39 nickel-positive individuls. Consequently, 15% of the rections would hve been missed with reding only t D3 4. The clculted sensitivity, specificity, nd positive nd negtive predictive vlues for the self-test re shown in Tble III. The sensitivity for the self-test ws 72%, when compred with gold stndrd ptch test method. The proportion of greement ws 86%. However, the vlidity of the self-test ws higher when compred with ptch test reding t D3 4 only, yielding sensitivity of 77%. When compring the ptients reding of the self-test with the dermtologists reding of the self-test on the rm on the sme dy (D3 4), somewht better greement ws found (Tble IV). The sensitivity ws 89% nd the positive predictive vlue ws 76%. However, the highest greement ws found when compring the dermtologists reding of the self-test on the rm with the reding of ptch test on the bck on the sme dy (D3 4). Both the sensitivity nd the positive predictive vlue were then 84% nd the proportion of greement ws 94% (Tble V). Thirteen individuls reported nickel llergy from self-test, but were nickel negtive ccording to the gold stndrd ptch test. Among the flse-positives, 54% hd history of topic dermtitis vs. 43% mong the totls. Frgrnce llergy Reding D3 4 Gold stndrd % (95% CI) n % (95% CI) n Sensitivity 77 (61 89) 30/39 72 (57 84) 33/46 Specificity 89 (83 94) 136/ (85 95) 132/145 Positive predictive vlue 65 (50 79) 30/46 72 (57 84) 33/46 Negtive predictive vlue 94 (89 97) 136/ (85 95) 132/145 Proportion of greement 87 (81 91) 166/ (81 91) 165/191 Gold stndrd is the conclusion from ptch test reding by dermtologist on D3 4 nd D7. CI: confidence intervl. The self-test for frgrnce llergy gve 7 positive individuls, wheres the gold stndrd ptch test gve 9 positive rections. Due to the low number of frgrnce-positive individuls, we did not perform ny further nlysis on frgrnce llergy. Tble IV. Self-test result regrding nickel llergy red by the ptient in reltion to the dermtologist s reding of the sme test (on the rm) D3 4 Self-test, ptient s reding, rm Dermtologist s reding D3 4, rm, n Positive Negtive Totl Positive Negtive Rections clssed s +, ++, or +++ re ll regrded s positive. Tble V. Nickel ptch test results red by the dermtologist. Comprison between ptch test (self-test pplied by the ptient) on the rm nd stndrdized ptch test on the bck Dermtologist s reding D3 4, rm Drop-outs In totl, 243 ptients were included, 52 (21%) of the ptients did not complete the study. Seventeen of those did not successfully pply the self-test, six chnged their minds, five did not ttend the second reding, nd nother eight forgot the envelope with the result. For the remining 16 individuls, no reson ws given. The proportion of men/women ws similr mong the drop-outs nd the prticipnts, nd the men ge ws 40 vs. 44 yers for drop-outs nd prticipnts, respectively. DISCUSSION Dermtologist s reding D3 4, bck, n Positive Negtive Totl Positive Negtive Rections clssed s +, ++, or +++ re ll regrded s positive. The present study hs vlidted tool for epidemiologicl surveillnce of nickel llergy. It is of importnce to follow the prevlence of contct llergy in the generl popultion. However, ll the vilble methods hve limittions. Stndrdized ptch testing with redings performed by dermtologist on D3 4 nd D7 is the most relible method to investigte the occurrence of contct llergy nd hs, in the present study, been used s the gold stndrd. However, popultion-bsed studies tht include ptch tests re expensive nd hve logisticl problems, since ech individul hs to visit the dermtology deprtment severl times. Thus, in most popultion-bsed studies including ptch testing, only one reding is performed. When studying the prevlence of nickel llergy with only one reding performed on D3, 10 15% of the positive ptch test rections to nickel my be missed becuse of delyed rections (16). Results from the present study were similr, nd showed tht 15% (7/46) of positive ptch test rections would hve been missed with only one reding. A study by Thyssen et l. (17) found tht, with one reding performed on D2, 18 30% of positive ptch test rections to nickel sulphte my be missed. Uter et l. (18) compred ptch test results for nickel t D2 nd D3, nd found tht 26.6% of the positive rections ppered t D3 only, while 3.6% of wek rections t D2 were not considered llergic t D3. Most studies on the occurrence of contct llergy re bsed on clinicl dt from ptients t dermtology clinics (19 21). Obviously, people referred to dermtology deprtment constitute selected group of ptients

5 Vlidtion of self-testing for nickel llergy prevlence 529 with skin symptoms, such s eczem, nd cnnot be considered representtive of the generl popultion. Another pproch for epidemiologicl surveillnce is the CE-DUR method, which is discussed in studies from Germny nd Denmrk (22, 23). This method mkes ssumptions in order to estimte the 10-yer prevlence of contct llergy, using ntionl ptch test sles informtion s well s clinicl dt. In the Germn study (22), the uthors concluded tht the morbidity dt concerning contct llergy were in good ccordnce with dt from popultion-bsed epidemiologicl studies. However, regrding nickel sensitiztion, the 9-yer prevlence ws 2.3% nd 5.5% in different models, which is considerbly lower thn in studies in the generl popultion (3, 24). In Denmrk the 10-yer prevlence of contct llergy mesured by CE-DUR ws slightly lower thn the previous prevlence estimtes from popultion-bsed studies in Denmrk (23). The use of questionnires is nother method for epidemiologicl studies. However, estimting the prevlence of contct llergy from self-reports seems to be difficult. Previous studies hve shown low vlidity in predicting nickel llergy, with positive predictive vlues of 31% (12), 54% (11, 25) nd 59% (9). Thus, questions bout self-reported nickel llergy re not useful in epidemiologicl studies s they strongly overestimte the true prevlence. The present study investigtes whether self-testing might be method sensitive enough to follow the prevlence of nickel llergy. The use of self-test for surveillnce of contct llergy would be beneficil nd convenient for the investigtor s well s for the test persons. It would be cost-effective to distribute the test nd instructions by post nd receive the nswer without the study subjects needing to rrnge ppointments, trnsporttion nd tke time off work. To the best of our knowledge the only previous report concerning contct llergy nd self-testing is conference presenttion (26). Tht study found proportion of greement for nickel nd frgrnce mix together of 89.5% nd sensitivity of 97.5%. In the present study the sensitivity regrding nickel llergy ws 72% nd the proportion of greement ws 86% when compring the self-test for nickel with the gold stndrd ptch test. However, most vlidtions concerning contct llergy include only one reding, nd when the self-test results were compred with the results red by dermtologist on D3 4 in this study, the sensitivity ws 77%. In the present study, there were 13 flse-positive nswers regrding nickel llergy using the self-test nd 13 flse-negtive estimtions. A limittion of the self-test is tht only one reding is performed, which explins some of the flse-negtive nswers. Tble IV shows the discrepncies between the ptients nd the dermtologists reding. Our ssumption is tht these discrepncies were minly due to the interprettion of irritnt or doubtful rections s positives by the ptient. The proportion of ptients with history of topic dermtitis ws higher mong the flse-positives thn mong the group s whole, which might contribute to more irritnt rections nd, consequently, flse-positive evlutions. The skin of the bck is more responsive thn tht of the rms nd thighs, nd only the upper bck is recommended for routine dignostic ptch testing (27, 28). For prcticl resons, however, self-test hs to be pplied on the rm. Tble V illustrtes the discrepncies in reltion to the test res in the present study. Comprison of the results from the two test res shows tht the number of flse-positives ws the sme s the number of flse-negtives, nd the test re ws ccordingly not of gret importnce in this study. The study ws performed t three different dermtology deprtments, nd, consequently, different dermtologists performed the ptch test redings. This might hve influenced the results, but to minimize the risk, ll ptch tests were red by specilists in dermtology. In totl, 243 individuls were included in this study, but the proportion of drop-outs ws high, t 21%. Some ptients hd problems pplying the self-test. More clerly written instructions would probbly improve the prticiption rte. All methods vilble for estimtion of the occurrence of nickel llergy hve limittions, prcticl, economic, or regrding vlidity. Awreness of these limittions is importnt when evluting results from epidemiologicl studies. In the present study self-testing ppers to be resonble lterntive method for estimtion of the prevlence of nickel llergy. However, the positive predictive vlue is criticlly dependent on the popultion chosen nd the prevlence of disese within tht popultion. This mens tht the positive predictive vlue my not be trnsferble from the ptient popultion in the present study to the generl popultion. Further testing in the generl popultion will be needed to determine the usefulness of self-testing s n epidemiologicl tool to follow the prevlence of nickel llergy. ACKNOWLEDGEMENTS The uthors thnk Inglill Erikssohn, Ingrid Eriksson nd Ingliss Bryngelsson for skilful ssistnce. Anders Mgnuson is grtefully cknowledged for sttisticl ssistnce. The study ws supported by the Reserch Committee of Örebro County nd grnts from the Welnder-Finsen Foundtion. The uthors declre no conflict of interest. REFERENCES 1. Thyssen JP, Linneberg A, Menne T, Johnsen JD. The epidemiology of contct llergy in the generl popultion prevlence nd min findings. Contct Dermtitis 2007; 57: Dotterud LK, Smith-Sivertsen T. Allergic contct sensiti-

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