Validity of Self-reported Skin Screening Histories

Transcription

1 American Journal of Epidemiology Copyright 2004 by the Johns Hopkins Bloomberg School of Public Health All rights reserved Vol. 159, No. 11 Printed in U.S.A. DOI: /aje/kwh143 Validity of Self-reported Skin Screening Histories J. F. Aitken 1,2, P. H. Youl 1, M. Janda 1,3, M. Elwood 4, I. T. Ring 5, J. B. Lowe 6, and D. W. Firman 7 1 Epidemiology Unit, Queensland Cancer Fund, Brisbane, Queensland, Australia. 2 School of Population Health, University of Queensland, Queensland, Australia. 3 School of Public Health, Queensland University of Technology, Brisbane, Queensland, Australia. 4 National Cancer Control Initiative, Carlton, Victoria, Australia. 5 Health Information Centre, Queensland Health, Brisbane, Queensland, Australia. 6 Department of Community and Behavioral Health, College of Public Health, University of Iowa, Iowa City, IA. 7 Office of Economic and Statistical Research, Queensland Treasury, Brisbane, Queensland, Australia. Received for publication October 22, 2003; accepted for publication December 23, Screening by whole-body clinical skin examination may improve early diagnosis of melanoma and reduce mortality, but objective scientific evidence of this is lacking. As part of a randomized controlled trial of population screening for melanoma in Queensland, Australia, the authors assessed the validity of self-reported history of whole-body skin examination and factors associated with accuracy of recall among 2,704 participants in Approximately half of the participants were known to have undergone whole-body skin examination within the past 3 years at skin screening clinics conducted as part of the randomized trial. All positive and negative selfreports were compared with screening clinic records. Where possible, reports of skin examinations conducted outside the clinics were compared with private medical records. The validity of self-reports of whole-body skin examination in the past 3 years was high: Concordance between self-reports and medical records was 93.7%, sensitivity was 92.0%, and specificity was 96.3%. Concordance was lower (74.3%) for self-reports of examinations conducted in the past 12 months, and there was evidence of telescoping in recall for this more recent time frame. In multivariate analysis, women and younger participants more accurately recalled their history of skin examinations. Participants with a history of melanoma did not differ from other participants in their accuracy of recall. mass screening; melanoma; mental recall; sensitivity and specificity; skin Melanoma is a public health problem of increasing magnitude in the United States (1). Approximately 54,200 new cases of melanoma and approximately 7,600 deaths from melanoma have been estimated for 2003 (2). In Australia, the incidence of melanoma increased by 2.5 percent per year in men and by 1.6 percent per year in women from 1990 to 1999 (3). In 1999, in a population of approximately 19,000,000, there were 4,627 new cases of melanoma and approximately 1,000 deaths (3). Survival is strongly related to the thickness of the tumor at diagnosis (4, 5). Screening for melanoma by whole-body clinical skin examination has the potential to improve early diagnosis and reduce melanoma mortality (6, 7). However, at present, there is no objective evidence of benefit, and the US Preventive Services Task Force has stated that the evidence is insufficient to recommend for or against routine screening for skin cancer using a total-body skin examination for the early detection of cutaneous melanoma, basal cell cancer, or squamous cell skin cancer (8, p. 44). In order to add to the available evidence, accurate information on the prevalence of screening is needed for assessment of the impact of any population-based skin screening program (9, 10). Skin screening examinations for melanoma commonly do not result in a laboratory or pathology report and are often not documented in the medical record (7); thus, almost all information about skin screening prevalence is based on patients self-reports (7, 11 14). There is virtually no information available on the accuracy of such reports, in contrast to self-reports of breast, colorectal, and cervical cancer screening, which have been successfully validated against laboratory or medical records. For example, Norman et al. (15) reported sensitivities of over 0.90 and specificities Correspondence to Dr. Joanne Aitken, Epidemiology Unit, Queensland Cancer Fund, P.O. Box 201, Spring Hill, Brisbane, Queensland 4004, Australia ( joannea@qcfepi.org.au). 1098

2 Validity of Self-reported Skin Screening Examinations 1099 of over 0.80 for self-reported mammography screening compared with facility records among cases and controls. Using a national breast screening database, Barratt et al. (16) found that 91 percent of women reported their mammography date accurately to within 12 months. Baier et al. (17) assessed the validity of self-reported colorectal cancer screening against health maintenance organization records and found 96 percent sensitivity for fecal occult blood testing, 95 percent for sigmoidoscopy, and 96 percent for colonoscopy. Another study that compared recall of six early cancer detection procedures with health maintenance organization records (18) found greater accuracy of recall for procedures which resulted in a test report, such as mammography (concordance of 84 percent), Papanicolaou smears (78 percent), or fecal occult blood testing (79 percent), than for those which generated only a physician s note, such as clinical breast examination (70 percent). The present study was conducted as part of the first phase of a randomized controlled trial of melanoma screening in which whole-body skin examinations were offered to residents of intervention communities. Within the trial, records were kept of all such skin screening examinations carried out over a 3-year period, providing us with a unique opportunity to verify participants self-reported skin screening history. The aim of this study was to assess the validity of recall of whole-body clinical skin examination in comparison with medical records and to determine factors associated with accuracy of recall. MATERIALS AND METHODS The randomized trial of melanoma screening A cluster randomized controlled trial with the aim of assessing whether melanoma screening reduces mortality from melanoma was conducted between 1998 and 2001 in the state of Queensland, Australia. The design of the trial is described in detail elsewhere (9). During the first phase of the trial, 18 Queensland communities were selected and randomly allocated to receive either a 3-year communitybased melanoma screening intervention (nine intervention communities) or normal practice (nine control communities). The intervention, named the SkinWatch Program, consisted of a community education program, an education and support program for primary care physicians designed to improve their early diagnosis of melanoma, and the provision of open-access skin screening clinics (SkinWatch clinics) staffed by local primary care physicians and physicians hired from outside the communities (J. B. Lowe, College of Public Health, University of Iowa, unpublished manuscript). It was the aim of the SkinWatch intervention to increase community participation in skin screening by medical practitioners. Attendance at SkinWatch clinics was by appointment. Prior to the examination, participants were required to sign a consent form and complete a questionnaire about sociodemographic characteristics, melanoma risk factors, and attitudes. During the 3-year intervention period, a total of 16,383 people visited the SkinWatch clinics. For each of these participants, name, date of birth, address, telephone number, and questionnaire information was stored in the SkinWatch clinic database. Study subjects The validation study was conducted in three of the nine intervention communities. Subjects were drawn from two sources within these three communities. First, we selected all 3,878 residents aged 30 years or more listed in the Skin- Watch clinic database who had had a skin examination at a SkinWatch clinic in the past 3 years. Of these persons, we excluded 1,720 people who had participated in a recent survey of skin screening and whose accuracy of recall in this second survey may therefore have been better than normal. Those excluded were comparable to participants with regard to age, sex, and melanoma risk factors. A further 586 persons were uncontactable (their telephone had been disconnected (n = 238), they had moved (n = 187), there was no answer (n = 137), or the telephone line was nonresidential (n = 24)), 112 were unavailable within the study time frame, and 30 were unable to speak English. Of the remaining 1,430 residents, 1,304 (91.2 percent) agreed to take part, and 126 (8.8 percent) refused participation. The second group of subjects was drawn at random from a commercially available telephone list (Desktop Marketing Systems Pty. Ltd., Boronia, Victoria, Australia) containing virtually all residential telephone numbers in the geographic areas involved in the study. From this list, we excluded the telephone numbers of all persons known to have had a skin examination at a SkinWatch clinic and all those who had participated in a recent skin screening survey. Of 3,164 residences contacted, 1,769 contained a potentially eligible subject (i.e., someone aged 30 years or more and of the required gender (we used a quota sampling scheme to ensure equal numbers of men and women) who was able to speak English and was available within the study time frame), and 1,400 (79.1 percent) agreed to take part. Thus, the final sample comprised 2,704 participants, including 1,304 known to have had a skin examination at a SkinWatch clinic in the past 3 years and 1,400 known not to have had such an examination (overall consent rate = 84.5 percent). Data collection All participants completed a structured computer-assisted telephone interview administered by professional telephone interviewers. Self-reported clinical whole-body skin examination. Participants were randomly assigned to receive one of two versions of a question assessing whole-body skin examination in the past 3 years. The two groups were similar in terms of their sociodemographic composition. In the total sample of 2,704 participants, 1,598 people were asked, In the past 3 years, has a doctor deliberately checked the skin on your whole body? Usually this would involve taking your clothes off at least down to your underwear (i.e., bra and underpants). For assessment of the accuracy of reports related to the more recent past, the same question was repeated in this group but asking only about the past 12 months. The remaining sample

3 1100 Aitken et al. TABLE 1. Concordance, sensitivity, and specificity of self-reports of whole-body clinical skin examination during the past 3 years as compared with SkinWatch clinic and other medical records (n = 2,393), Queensland, Australia, 2001 No. of participants* Concordance Sensitivity Specificity All validated participants 2, Sociodemographic data Sex Male 1, Female 1, p for trend Age group (years) p for trend 0.01 Education Primary school Some high school Completion of high school Trade certificate University degree p for trend 0.35 Employment Full-time 1, Part-time/casual Not working (retired/home duties) p for trend 0.92 of participants (n = 1,106) received a slightly shorter question: During the past 3 years, has a doctor deliberately checked the skin on all or nearly all of your whole body? All those who reported having undergone a whole-body skin examination were asked for the location and date of this examination (Skin- Watch clinic, primary care physician s or dermatologist s office, or other venue). Sociodemographic characteristics, attitudes toward skin cancer, and skin cancer risk factors. Other information collected during the interview included gender; age (30 39, 40 49, 50 59, 60 69, or 70 years); educational level (primary school (7 years of schooling), some high school (10 years of schooling), completion of high school (12 years of schooling), trade certification (e.g., plumber, electrician), or university degree ( 13 years of schooling); employment (full-time, part-time/casual, or not working); and yearly household income before taxes (in Australian dollars: Table continues <$20,000, $20,000 $60,000, >$60,000, or unwilling to answer). Participants were asked how concerned they were about skin cancer (very concerned, somewhat concerned, or not concerned at all); how likely they thought they were to get skin cancer in the future (not at all likely, somewhat likely, or very likely); whether they had had a mole or skin spot removed in the past; whether they had ever been diagnosed with melanoma; and whether they had been diagnosed with any other sort of skin cancer. Self-reported history of melanoma was compared with cancer registry records. Validation of self-reported skin screening We compared all participants self-reports with the Skin- Watch clinic records. Where possible, we also checked the private medical records of all participants who indicated that they had received a whole-body skin examination from a

4 Validity of Self-reported Skin Screening Examinations 1101 TABLE 1. Continued No. of participants* * Numbers in some subgroups do not total 2,393 because of missing values. Concordance Sensitivity Specificity Yearly household income (Australian dollars) <$20, $20,000 $60, >$60, Unwilling to answer p for trend 0.75 History of skin cancer Self-reported history of melanoma No 2, Yes p for trend 0.20 Self-reported history of nonmelanoma skin cancer No 2, Yes p for trend 0.73 Ever had a mole/spot removed No 1, Yes 1, p for trend Attitudes toward skin cancer Concerned about skin cancer Not very concerned/not concerned at all 1, Very concerned 1, p for trend 0.92 Perceived likelihood of developing skin cancer in the future Not very likely/not at all likely 1, Very likely p for trend physician outside the SkinWatch clinics. For each participant who reported a skin examination that was subsequently confirmed, we calculated the interval between the date of the interview and the actual date of the skin examination as recorded in the medical record. With regard to checking of negative reports, we were able to confirm reports of nonattendance at SkinWatch clinics, but we did not attempt to check negative reports in private physicians medical records; that is, we did not check medical reports for patients who stated that they had not visited their own physician for a skin examination. Of the 2,704 total participants, 563 stated that they had visited a physician outside the SkinWatch clinic for a skin examination in the past 3 years; 296 (52.6 percent) gave written consent for us to contact their physician for confirmation of this. Thirty-eight physicians were contacted by mail to participate in the present study, of whom 28 (73.7 percent) agreed. Copies of participants consent forms were mailed to the nominated physicians. Physicians were asked to indicate on an attached form whether there was a record of a whole-body skin examination and the exact date (or dates) of the examination, or to indicate as much if there was no record of such an examination. Responses were received from the physicians of 252 (85.1 percent) participants. The remaining 311 participants for whom we were not able to check private physicians records were excluded from the sample, generating a final sample for analysis of 2,393. The 311 excluded participants were similar to the rest of the sample in terms of age, sex, and education.

5 1102 Aitken et al. TABLE 2. Validation of self-reported history of whole-body skin examination by a physician (n = 2,393), Queensland, Australia, 2001* * No private physician s record was available for 311 participants; therefore, those participants were not included in the present analysis. CI, confidence interval. Data analysis We assessed concordance as the proportion of total selfreports (either positive or negative) that were accurate in comparison with medical records. Cohen s kappa statistic was calculated as a measure of agreement between selfreports and medical records, correcting for chance agreement (19). Additionally, we calculated the sensitivity (percentage of positive medical records accurately reported by participants) and specificity (percentage of negative medical records accurately reported by participants) of self-reports (table 1). The sensitivity, specificity, and concordance of self-reported whole-body skin examination during the past 3 years were compared between sociodemographic groups and according to attitudes toward skin cancer and skin cancer risk factors using chi-squared tests for trend (table 2). Multiple logistic regression analysis was used to examine factors associated with concordance of selfreported whole-body skin examination within the past 3 years. All analysis was undertaken using the SPSS statistical package (version 11.5; SPSS, Inc., Chicago, Illinois). Ethics Time period of recall and version of question posed to participant Medical records (included SkinWatch clinic records and other records): Participant s response: This study was approved by the Behavioural and Social Sciences Research Ethical Review Committee of the University of Queensland. Yes No Yes No Yes (a) Yes (b) No (c) No (d) RESULTS Concordance (a + d)/ (a + b + c + d) Kappa Characteristics of participants 95% CI Sensitivity Specificity a/(a + c) d/(b + d) Past 3 years Version 1 (n = 1,416) In the past 3 years, has a doctor deliberately checked the skin on your whole body? Usually this would involve taking your clothes off at least down to your underwear (i.e., bra and underpants) , Version 2 (n = 977) In the past 3 years, has a doctor deliberately checked the skin on all or nearly all of your whole body? , Versions 1 and 2 combined (n = 2,393) 1, , Past 12 months Version 1 (n = 1,410) In the past 12 months, has a doctor deliberately checked the skin on your whole body? Usually this would involve taking your clothes off at least down to your underwear (i.e., bra and underpants) , Approximately equal numbers of males and females participated in the telephone survey (48.9 percent and 51.1 percent, respectively) (table 1). More than half of the participants were aged years (55.2 percent). More than half of all participants had received 12 or more years of schooling. When asked about attitudes toward skin cancer, more than half (51.5 percent) indicated that they were very concerned about skin cancer, and 40 percent thought they were very likely to get skin cancer in the future. Overall, 4.0 percent of participants reported a history of melanoma, 11.6 percent reported a history of nonmelanoma skin cancer, and 53.3 percent said they had had a mole or skin spot removed in the past. Sensitivity, specificity, and concordance: whole-body skin examination in the past 3 years. Among the 2,393 participants, 1,366 reported having had a whole-body skin examination carried out by a primary care physician within the past 3 years (1,163 in SkinWatch clinics and an additional 203 at a physician s office outside the clinics), and 1,027 reported that they had not received a skin examination in the past 3 years. We confirmed 1,147 (98.6 percent) reports of skin examinations at SkinWatch clinics and 184 (90.6 percent) reports of skin examinations outside the clinics, for a total of 1,331 (97.4 percent) true-positive reports (table 2). The percentage of correct reports was similar for version 1 and

6 Validity of Self-reported Skin Screening Examinations 1103 version 2 of the question (97.7 percent and 97.1 percent, respectively). Among the 1,027 people who reported having had no skin examination in the past 3 years, 116 had actually received an examination at the SkinWatch clinics, giving us a total of 911 (88.7 percent) true-negative reports (assuming no overreporting of private skin examinations). Overall concordance between self-reports and medical records was 93.7 percent. The sensitivity of self-reports was 92.0 percent overall, and sensitivity was similar for both versions of the question (92.1 percent and 91.8 percent). Specificity was 96.3 percent overall and was also similar for both versions of the question (96.5 percent and 96.0 percent). We repeated this analysis, assuming the same amount of underreporting of private skin examinations (116 false-negative reports) as we had observed for SkinWatch clinic examinations, that is, a total of 232 false-negative reports. Under this assumption, sensitivity was reduced to 85.2 percent and specificity was reduced slightly to 95.8 percent, with overall concordance of 88.9 percent. Sensitivity, specificity, and concordance: whole-body skin examination in the past 12 months. Participants recall of whole-body skin examination within the past 12 months was less accurate (74.3 percent) than recall for the past 3 years. The majority of errors were false-positive reports (n = 352), that is, overreporting of skin examinations within the past 12 months. In most cases (98 percent), the errors were due to telescoping underestimation of the amount of time elapsed since the last examination (table 1). There was no association of telescoping with gender or age. Similar degrees of telescoping could be seen with all levels of education, ranging from 73.4 percent for persons with a primary school education to 79.2 percent for those who had a trade certificate (p = 0.82). No associations with telescoping were seen for other sociodemographic factors or for skin cancer risk factors. Factors associated with accuracy of recall of skin examination. Concordance, sensitivity, and specificity according to sociodemographic characteristics, attitudes toward skin cancer, and skin cancer risk factors are presented in table 1. Women (95.2 percent) were more likely than men (92.1 percent) to recall a whole-body skin examination correctly (p = 0.002). There was a significant age trend, with persons aged 70 years or more recording the lowest concordance (90.5 percent). No other sociodemographic factors, such as income, education, or employment, were associated with concordance. Ninety-six participants reported a personal history of melanoma. Concordance for participants with a self-reported history of melanoma was 90.6 percent, as compared with 93.9 percent for those reporting no history of melanoma a difference that was not significant. Of the 96 participants who reported a history of melanoma, 76 (79.2 percent) consented to access to cancer registry records, and history of melanoma was confirmed for 28 (36.8 percent) of these persons. There was virtually no difference in sensitivity of recall of whole-body skin examination between participants with and without a confirmed history of melanoma (92.6 percent and 92.0 percent). Participants who reported a history of nonmelanoma skin cancer, removal of a spot or mole, or high susceptibility to development of skin cancer were less concordant in their recall of skin examinations than other participants. There was no association between level of concordance and concern about skin cancer (table 1). In multivariate modeling, after adjustment for all other variables, women were more likely than men (p for trend = 0.006) to report a skin examination accurately, while there was a tendency for older participants to recall a skin examination less accurately than younger participants (p for trend = 0.09). No other factors were significantly associated with accuracy of recall of skin examination. DISCUSSION Regular whole-body skin examination by a physician for the early detection of melanoma is recommended by various professional groups and could potentially reduce the number of melanomas detected at a late (thick) stage, thereby reducing melanoma mortality (7, 20). However, at present there is no objective evidence of the benefit of routine skin examination by a physician (8). Results of population-based surveys suggest that whole-body skin examinations by a physician are increasingly being initiated by both patients and doctors and that, in Australia at least, these examinations are targeted toward groups at highest melanoma risk (21; M. Janda, Queensland Cancer Fund, unpublished manuscript). However, all studies of skin examinations of which we are aware were based on participants self-reports, and virtually nothing is known about the accuracy of such measurements. We compared participants self-reports of whole-body clinical skin examinations conducted within the past 3 years with records of such examinations collected during a randomized trial of screening for melanoma. The concordance between self-reports and medical records was very high (93 percent), as was the sensitivity (92 percent) and specificity (96 percent) of self-reports, indicating that participants are able to recall this event accurately. Men and participants aged 70 years or older were less likely to recall skin examinations accurately. Increasing age was also reported to be inversely associated with recall of other screening procedures such as sigmoidoscopy, fecal occult blood testing, and Papanicolaou smear (17, 18). However, Newell et al. (22), in their study of cervical cancer and cholesterol screening, did not find any associations between accuracy of recall and sex, age, or education. Based on the current results, the validity of self-reported skin screening history within both skin clinics and private physicians practices compares favorably with that of selfreports of mammography and other screening procedures. Concordance between self-reports and mammographic records ranges from 83 percent (18, 23) to 94 percent (16). Warnecke et al. (24) summarized the validity of selfreported Papanicolaou smears (12 studies; overall concordance = 65 percent), mammograms (eight studies; overall concordance = 86 percent), and clinical breast examinations (three studies; overall concordance = 70 percent). Gordon et al. (18) reported sensitivities for self-reports of 98 percent for mammograms, 97 percent for Papanicolaou smears, and 91 percent for fecal occult blood testing, while Norman et al. (15) reported sensitivities of 93 percent for cases and 92 percent for controls as part of a case-control study on the

7 1104 Aitken et al. efficacy of screening mammography. Somewhat lower sensitivities (76 82 percent) have been reported for prostatespecific antigen testing (25, 26) and digital rectal examination (78 percent) (18). Within the current study, concordance was significantly lower when participants were asked about the past 12 months than when they were asked about the past 3 years; this was largely due to participants underestimating the amount of time elapsed since the skin examination had actually been performed. This phenomenon of a patient s recalling a test or procedure as occurring more recently than it actually did is referred to as telescoping (18, 24, 27). McGovern et al. (28) found that up to one third of participants recalled having their mammograms more recently than they actually did. Additionally, Caplan et al. (23) found that approximately 28 percent of women in their study underestimated the time that had elapsed since their mammogram. Some limitations of our study must be noted. Our sample was drawn from residents living within intervention communities of a randomized controlled trial of melanoma screening. Therefore, our participants may have been more aware of and more interested in skin cancer and skin screening than could be expected in other populations because of publicity associated with the trial. This could have resulted in somewhat better recall of skin examinations than could be expected in the general population, though we have no evidence of this. The recall of whole-body skin examinations that we observed is well within figures reported for other self-reported health behaviors (16 18, 23). The response rate within our study was high, with 85 percent of all eligible residents agreeing to participate. This compares favorably with other validation studies, where response rates varied between 33 percent for a study of mammogram screening involving women in a county health system (29) to percent for studies on the accuracy of recall of Papanicolaou smears, cholesterol screening, and other screening procedures (16, 18, 22, 23). Although we had complete records of all whole-body skin examinations performed at SkinWatch skin clinics, we could only check medical records for approximately 45 percent of whole-body skin examinations reported to have occurred outside the clinics, in private practices. The accuracy of reporting was similar for self-reported SkinWatch examinations and examinations conducted in private practices, and the sociodemographic characteristics of participants for whom we were not able to access medical records did not differ from those of other participants in any measurable way. We have no reason to believe that their accuracy or reporting would have differed from that of the remainder of the sample. Although we were able to confirm negative reports of skin examinations through the SkinWatch clinic records, we did not attempt to check negative reports of skin examinations by private physicians. Our analysis suggests that had we done this, our results are unlikely to have changed significantly. Accuracy of recall depends to a significant extent on the precise wording of survey questions (30). Baier et al. (17) have noted the importance of accurate wording in surveys on colorectal cancer screening. Following the results of their pilot work, these authors reworded their questions on fecal occult blood testing and were able to increase the accuracy of recall from 62 percent to 96 percent in their final sample (17). Within the present study, concordance, sensitivity, and specificity were similar for the two versions of the question on skin screening, perhaps because of a number of key words common to both questions, such as has a doctor deliberately checked. The greater detail given in version 1 of the question ( this would involve taking your clothes off at least down to your underwear ) does not seem to have added to the accuracy of recall. On this basis, we would recommend the use of the second, shorter version in future studies. Confirmation of a self-reported history of melanoma was low within the present study (37 percent), in contrast to a recent study of US teachers (31). That study compared selfreported cancer histories with cancer registry records and found 73 percent sensitivity for persons reporting a history of melanoma and 54 percent for other types of skin cancer. The most likely explanation for overreporting of melanoma in this Queensland population is confusion between melanoma and other, more common actinic neoplasms (solar keratoses and basal and squamous cell carcinoma) and confusion with benign nevi, which are highly prevalent in this sun-exposed population and are commonly excised to exclude melanoma. These sources of error have also been shown to result in substantial overreporting of family history of melanoma in Queensland (32). After adjustment for other variables such as sex and age, neither a self-reported history of melanoma nor a confirmed history of melanoma appeared to influence accuracy of recall of whole-body skin examinations. This finding is encouraging for case-control studies of melanoma screening utilizing self-reported history of skin examinations, since we found no evidence of bias in the way cases or controls reported their screening history. To our knowledge, this is the first study to have examined the validity of patient recall of whole-body clinical skin examination. The validity of self-reported whole-body clinical skin examination during the past 3 years was high and compares well with results observed in studies of other screening examinations. Telescoping was observed when participants were asked about undergoing a whole-body skin examination during the past 12 months; this suggests that future studies should restrict questioning to longer time intervals, such as the past 3 years. Overall, self-reports of whole-body skin examination seem to be a reliable source of data for epidemiologic studies, if the time frame is sufficiently wide. Because self-reporting will continue to be the most widely used source of data for evaluating the prevalence of screening behavior, attention must be given to accurate wording of questions in order to clarify sufficiently the behavior in question and the time frame of recall. ACKNOWLEDGMENTS This study was supported by the Queensland Cancer Fund and Queensland Health.

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