Validity and reliability of a questionnaire designed to assess risk factors of pancreatic cancer in Iran

The objective of this study is to develop a questionnaire to study risk factors of pancreatic cancer in Iran and to assess its reliability and validity. Following a comprehensive literature search and consulting with six expert gastroenterologists,these domains were included in the questionnaire: demographic variables; anthropometric indices; socioeconomic status indicators; signs and symptoms of the current disease; occupational history and exposure to certain physical and chemical agents; medical and drug history; family history of cancer; history of alcohol, tobacco, or opium use; history of tea and coffee consumption; pregnancy and menstrual data (only for women); and dietary habits and cooking methods. A total of 113 questions were developed and included in the questionnaire. Content validity was assessed by six gastroenterologists, three lay experts, and one methodologist. Reliability was evaluated using test-retest. Ten case subjects and 15 control subjects completed the questionnaire twice with time intervals of two or three weeks. Overall, the validity and reliability of the questionnaire were acceptable. Item content validity index for clarity was above the predetermined level of 0.80 or higher for 112 (out of 113) questions. The corresponding index for relevancy was 0.80 or higher for 111 (out of 113) questions. The overall scale validity index for clarity and relevancy were 0.97 and 0.96, respectively. Inter-rater agreement for clarity and relevancy were 0.81 and 0.83 respectively. The scale comprehensiveness score was 100%. Regarding reliability, the intraclass correlation coefficients and kappa statistics were above the predetermined level of 0.70, except for four items. For the small minority of items that did not meet the predetermined standards (0.80 for validity and 0.80 for reliability), modifications were made based on consensus. The questionnaire can be used for research purposes in the relevant studies.