Comparison of surrogate with self-respondents regarding medical history and prior medication use

Background The self-report of medical history and medication use is a common feature of epidemiological research. Methods In a unique re-interview study, we evaluated the concordance of medical conditions and past medication use reported in two similar interviews 5 years apart. Results In 196 re-interviews with the subjects themselves, and in 107 with next-of-kin of subjects who died after the first interview, agreement was good or excellent (kappa greater than or equal to0.40) for 90% (9/10) of the conditions asked about in the personal medical history for both next-of-kin and self-respondents. Agreement was excellent (kappa >0.75) for two conditions, high blood pressure and hysterectomy, among self-respondents. Self- and surrogate respondents also showed similar reproducibility for prescription medications. bur next-of-kin respondents tended to have poor agreement (kappa <0.40) for over-the-counter (OTC) medications such as antacids, antihistamines, and analgesics. Next-of-kin also less reliably reported a family history of cancer. When analyses were stratified by type of surrogate respondent, concordance between the two interviews was generally higher for spouses than for other surrogate respondents. Conclusions This research demonstrates that personal medical history and prescription medication use may be as reliably reported by next-of-kin as self-respondents, but suggests that additional information may be needed to validate measures of OTC medication use and family history of cancer for next-of-kin respondents, possibly through the review of hospital records.