Does the mode of questionnaire administration affect the reporting of urinary symptoms?

OBJECTIVES: To assess the effect of modes of administration (self-administered questionnaires, oral face-to-face interview, and telephone interview) on responses to the American Urological Association Symptom Index (AUASI) in randomly selected community men.
METHODS: An age-stratified random sample of 475 white male residents of Olmsted County, Minnesota, aged 40 to 79 years, without prior prostate surgery or prostate cancer were queried about urinary symptom frequency twice at baseline and twice approximately 2 years later using questions with wording similar to the AUASI: At baseline and first follow-up, questionnaires were self-administered initially, followed by a structured interview by a female urology nurse within 2 to 28 weeks. A subset of 200 randomly selected men received a telephone interview by a female research assistant following the self-administered questionnaire given at a second follow-up approximately 4 years after baseline.
RESULTS: Mean symptom scores obtained by oral interview were 1 to 2 points lower than those from self-administered questionnaires (P < 0.01). In a random subset (n = 200) interviewed by telephone, mean AUASI scores were as much as 4 points lower than those from self-completed questionnaires.
CONCLUSIONS: Values of the AUASI obtained by interviewer administration may be lower than those obtained by self-administered questionnaires. When assessment of change in urinary symptoms over time is of interest, the same standardized method of questionnaire administration should be used at baseline and follow-up evaluations to avoid introducing artifactual differences related to the mode of administration.