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Background. Undisclosed use of illicit drugs and prescription controlled substances is frequent in some settings. The aim of the present study was to estimate the reliability of self-reported use of amphetamine, barbiturates, benzodiazepines, cannabinoids, cocaine, methadone, and opiates among acutely hospitalized medical patients. Methods. Patients admitted to an acute medical department were interviewed about their drug use. Patients provided blood and urine samples for drug analysis. Results of a toxicology screen were compared to self-reported drug use. Toxicology screens positive for drugs not reported during the interview were only considered truly positive after verification by a substance specific analysis. Results. Five hundred patients were included. The median age was 72 years and 298 (60%) were female. In total, 103 patients (21%) reported use of opiates and 65 patients (13%) used benzodiazepines. Only 8 patients reported use of illicit drugs (cannabinoids, 2%). Toxicology analyses were performed in a randomly selected sub-sample of 100 patients. Among 27 patients (27%), the analyses indicated use of one or more drugs, mainly benzodiazepines (15 patients), morphine (12 patients) or cannabinoids (5 patients). Another 6 patients had screenings unexpectedly positive for opiates, but the verification analysis indicated use of codeine-containing drugs. The overall sensitivity of self-reports in detecting drug use was 66%. The negative predictive value of a patient not reporting use of a drug was over 90% for all 7 drug-types screened. Conclusion. Among 100 randomly selected mainly elderly medical patients, undeclared use of illicit drugs was rare. However, some patients underreported use of benzodiazepines and cannabinoids.

The medication history among hospitalized patients often relies on patients' self-reports due to insufficient communication between health care professionals. The aim of the present study was to estimate the reliability of patients' self-reported medication use. Five hundred patients admitted to an acute medical department at a Danish university hospital were interviewed on the day of admission about their recent medication use. Blood samples drawn immediately after admission were screened for contents of 5 drugs (digoxin, bendroflumethiazide, amlodipine, simvastatin, glimepiride), and the results were compared to the patients' self-reported medication history. Information on prescribed drugs dispensed from any Danish pharmacy was collected from nationwide real-time pharmacy records. The authors performed home visits in a subgroup of 115 patients 4 weeks after their discharge. Stored drugs were inspected, and patients were interviewed about their drug use. Additional blood samples were drawn for drug analysis. The median age of included patients was 72 years, and 298 patients (60%) were women. Patients reported use of 3 (median) prescription-only medications (range, 0-14) during the structured interview. The congruence between self-report and drug analysis was high for all 5 drugs measured (all kappa0.8). However, 9 patients (2%) reported use of drugs that were not detected in their blood samples. In 29 patients (6%), the blood samples contained drugs not reported during the structured interview, but 14 of these drugs were registered in either hospital files or pharmacy records. Overall, the sensitivity of information from hospital files, structured interviews, and pharmacy records in identifying drug users was 87% to 93%, with no significant differences between methods. In conclusion, patients' self-reports are reliable when estimating recent use of cardiovascular and antidiabetic drugs.