Test-retest reliability of an icon/calendar-based questionnaire used to assess occupational history

Background Self-reported work histories can be critical for both epidemiolo gic and clinical purposes. However; the complexity of some work histories, such as those of migrant farm workers, can hamper recall, resulting in inac curate reporting. Memory aids may reduce such error This study, assesses th e reliability of work histories collected using such aids in the form of an icon/calendar-based questionnaire. Methods Thirty-one males engaged in farmwork and other manual labor for a m edian 28 years (range: 10-64) were interviewed twice, 8-14 months apart, ab out their lifetime employment. In each interview, subjects were asked about important life events, which were recorded with icons on a calendar They w ere then asked to recount their work history, including for each job the ta sks, crops or products handled, starting and ending dates, and location. Th is information was recorded, job-by-job, on the calendar with icons. Results Interquestionnaire agreement of cumulative reported employment dura tion (as measured by, the correlation coefficient) was moderate to high acr oss all time periods for certain crops (e.g., r = 0.69-0.92 for apple-relat ed work), by location (e.g., r = 0.76-0.95 for Washington State), and for a gricultural work in general (r = 0.67-0.94), but was lower for specific tas ks. Agreement of job counts was high for total work history for certain cro ps (e.g., r = 0.93 for apple-related work), by location (e.g., r = 0.90 for Washington State), and for agricultural work in general (r = 0.89), but pa radoxically decreased with proximity to the interview date. Agreement of bo th measures tended to be highest for those tasks and crops in which subject s reported spending the most time. Categorization of subjects into tertiles on the basis of either cumulative duration or counts produced results simi lar to those observed for job counts. Conclusions The icon-calendar questionnaire is an effective tool for estima ting cumulative duration of certain work categorizations among subjects wit h complex work histories. Published 2001 Wiley-Liss, Inc.