Talk is cheap: Measuring drinking outcomes in clinical trials

Objective: To evaluate the correspondence among measures of self-reported d rinking, standard biological indicators and the reports of collateral infor mants, and to identify patient characteristics associated with observed dis crepancies among these three sources of research data Method: Using data co llected from a large-scale clinical trial of treatment matching with alcoho lics (N = 1,726), these three alternative Outcome measures were compared at the time of admission to treatment and at 12 months after the end of treat ment. Results: Patient self-reports and collateral reports agreed most (97. 1%) at treatment admission when heavy drinking was unlikely to be denied. I n contrast, liver function tests were relatively insensitive, with positive serum gamma-glutamyl transpeptidase (GGTP) values obtained from only 39.7% of those who admitted to heavy drinking. At 15-month follow-up the corresp ondence between client self-report and collateral report decreased to 84.7% , but agreement with blood chemistry values increased to 51.6%. When discre pancies occurred, they still indicated that the client's self-report is mor e sensitive to the amount of drinking than the biochemical measures. Patien ts who presented discrepant results tended to have more severe drinking pro blems, more previous treatments, higher levels of pretreatment drinking and significantly greater levels of cognitive impairment, all of which could p otentially interfere with accurate recall. Conclusions: In clinical trials using self-selected research volunteers, biochemical tests and collateral i nformant reports do not add sufficiently to self-report measurement accurac y to warrant their routine use. Resources devoted to collecting these alter native sources of outcome data might be better invested in interview proced ures designed to increase the validity of self-report information.