Zajacova et al. Population Health Metrics 2010, 8:20 http://www.pophealthmetrics.com/content/8/1/20 Open Access RESEARCH © 2010 Zajacova et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Research Consistency and precision of cancer reporting in a multiwave national panel survey Anna Zajacova* 1 , Jennifer Beam Dowd 2,3 , Robert F Schoeni 4 and Robert B Wallace 5 Abstract Background: Many epidemiological studies rely on self-reported information, the accuracy of which is critical for unbiased estimates of population health. Previously, accuracy has been analyzed by comparing self-reports to other sources, such as cancer registries. Cancer is believed to be a well-reported condition. This paper uses novel panel data to test the consistency of cancer reports for respondents with repeated self-reports. Methods: Data come from 978 adults who reported having been diagnosed with cancer in at least one of four waves of the Panel Study of Income Dynamics, 1999-2005. Consistency of cancer occurrence reports and precision of timing of onset were studied as a function of individual and cancer-related characteristics using logistic and ordered logistic models. Results: Almost 30% of respondents gave inconsistent cancer reports, meaning they said they never had cancer after having said they did have cancer in a previous interview; 50% reported the year of diagnosis with a discrepancy of two or more years. More recent cancers were reported with a higher consistency and timing precision; cervical cancer was reported more inaccurately than other cancer types. Demographic and socio-economic factors were only weak predictors of reporting quality. Conclusions: Results suggest that retrospective reports of cancer contain significant measurement error. The errors, however, are fairly random across different social groups, meaning that the results based on the data are not systematically biased by socio-economic factors. Even for health events as salient as cancer, researchers should exercise caution about the presumed accuracy of self-reports, especially if the timing of diagnosis is an important covariate. Background Epidemiological studies often rely on self-reported infor- mation from population surveys. These data are used to calculate the incidence and prevalence rates of various health conditions in the population, to analyze their trends over time, to study their demographic, socio-eco- nomic, health-behavioral, and clinical correlates, and to inform health policy development and evaluation. The accuracy of reports is critical for unbiased and precise estimates of population health status. Numerous studies have evaluated the accuracy of self-reported health con- ditions by comparing them to other sources of informa- tion, such as medical records or, in the case of cancer, cancer registries. These studies have considered a single report per individual but did not address the reliability of individual self-reports over time. This paper examines the consistency of repeated reports of cancer occurrence and precision in the reported year of cancer diagnosis. Self-reports of health conditions often do not closely match "gold standard" information from medical records or medical examinations [1-5]. The accuracy of self- reports has been found to depend more on the type and severity of the health condition than on the respondent's demographic and socio-economic characteristics [4,6-9]. To some degree, younger, female, and more educated respondents provide more accurate reporting [6,10,11]. Almost always, more serious illnesses such as cancer are reported with higher accuracy than nonfatal chronic con- ditions such as hypertension [1,6,12]. As a life-threatening illness, cancer is considered a highly salient health condition that respondents are believed to recall accurately [11]. The assumption of accurate reporting may be one reason why the quality of cancer reports has attracted relatively few validation studies [13]. Some researchers have found retrospective * Correspondence: zajacova@uwyo.edu 1 Department of Sociology, University of Wyoming, Laramie, WY, USA Full list of author information is available at the end of the article