Agreement between self-reported illicit drug use and biological samples: a systematic review and meta-analysis
Background: We conducted a systematic review to estimate agreement between self-reported and biologically measured illicit drug use across populations and settings.
Methods: We systematically searched peer-reviewed databases and grey literature and included studies reporting 2x2 table counts or agreement estimates comparing self-reported and biologically measured use. With biological results considered the reference standard, we evaluated pooled estimates for overall agreement, sensitivity, specificity, false omission rates (proportion reporting no use that test positive) and false discovery rates (proportion reporting use that test negative) by drug class, potential consequences attached to self-report (i.e., work, legal or treatment impacts), and timeframe of use.
Results: From 7,066 studies, we extracted data from 198 eligible studies. Overall agreement ranged from good to excellent (>0.79). False omission rates were generally low while false discovery rates varied by setting. Specificity was generally high but sensitivity varied by drug, sample type, and setting. Self-report in clinical trials and situations of no consequences was generally reliable. For urine, recent self-report produced lower sensitivity and lower false discovery rates. Agreement was higher in studies that informed participants biological testing would occur (DOR: 2.9, 95% CI: 1.2-6.9) and studies rated as having low risk of bias (DOR: 2.9, 95% CI: 1.2-6.9). The main source of bias was biological assessments (53% studies).
Conclusion: Self-report can provide a reliable measure of illicit drug use for research purposes where there are no consequences of reporting use for the participant. Robust biological methods are more likely to provide reliable measures of recent use if there are problems with self-disclosure.