Comparison of ICD-9 Codes for Depression and Alcohol Misuse to Survey Instruments Suggests These Codes Should Be Used with Caution.

Background: Research suggests depression and alcohol misuse are highly prevalent among chronic hepatitis C (CHC) patients, which is of clinical concern.
Aims: To compare ICD-9 codes for depression and alcohol misuse to validated survey instruments.
Methods: Among CHC patients, we assessed how well electronic ICD-9 codes for depression and alcohol misuse predicted these disorders using validated instruments.
Results: Of 4874 patients surveyed, 56% were male and 52% had a history of injection drug use. Based on the PHQ-8, the prevalence of depression was 30% compared to 14% based on ICD-9 codes within 12 months of survey, 37% from ICD-9 codes any time before or within 12 months after survey, and 48% from ICD-9 codes any time before or within 24 months after survey. ICD-9 codes predicting PHQ-8 depression had a sensitivity ranging from 59 to 88% and a specificity ranging from 33 to 65%. Based on the AUDIT-C, the prevalence of alcohol misuse was 21% compared to 3-23% using ICD-9 codes. The sensitivity of ICD-9 codes to predict AUDIT-C score ranged from 9 to 35% and specificity from 80 to 98%. Overall 39% of patients reported ever binge drinking, with a sensitivity of ICD-9 to predict binge drinking ranging from 7 to 33% and a specificity from 84 to 98%. More than half of patients had either an ICD-9 code for depression, a survey score indicating depression, or both (59%); more than one-third had the same patterns for alcohol misuse (36%).
Conclusions: ICD-9 codes were limited in predicting current depression and alcohol misuse, suggesting that caution should be exercised when using ICD-9 codes to assess depression or alcohol misuse among CHC patients.