Validity of chronic drug exposure presumed from repeated patient interviews varied according to drug class.

Objective: To evaluate the validity of chronic drug exposure presumed from cross-sectional interviews taking reimbursement data as reference.

Study Design And Setting: The study concerned 2,985 elderly persons of the French Three-City cohort (1) who were interviewed on current drug use 2 and 4 years after inclusion and (2) whose reimbursement data were obtained from the main health care insurance system. Validity (sensitivity, Se; specificity, Sp; positive predictive value, PPV; negative predictive value, NPV) of chronic exposure presumed from follow-up interviews was investigated taking two exposure definitions from reimbursements as reference for the period between interviews: at least 80% coverage with and without a maximal time between reimbursements of 60 days.

Results: Using 80% coverage as reference, validity of interview data was substantial for cardiovascular and antithrombotic drugs (Se, 85.3-95.4%; Sp, 67.1-97.6%; PPV, 65.9-86.6%; NPV, 93.3-99.3%). For benzodiazepines, nonsteroidal anti-inflammatory drugs, or analgesics, validity was low especially owing to PPVs (15.8-51.4%).

Conclusion: Using reported use at cross-sectional interviews as a proxy for chronic exposure between interviews was valid for drugs used regularly but not so for drugs used more irregularly.