Reliability of two brief questionnaires for drug abuse treatment evaluation

The authors report the inter-interviewer reliability of two brief questionnaires developed to measure the effects of innovations in methadone maintenance. The instruments were designed to answer the research questions, but to intrude only minimally into the clinical assessment and treatment processes. The Initial Interview, completed at the time of admission, yielded information on 23 variables, and the Followup Interview, completed as soon as possible after the first anniversary of admission, yielded information on 20 variables. To assess reliability, a repeat interview was conducted by a different interviewer immediately after the first interview was completed. Repeat interviews were conducted with 19 subjects who completed the Initial Interview and 30 who completed the Followup Interview. Exact agreement was found in all the pairs of responses from the Initial Interview for 5 of the 6 categorical variables and 6 of the 17 quantitative variables. For the remaining 11 quantitative variables, the intraclass correlation coefficients ranged from .700 to .999. Exact agreement was found in all pairs of responses from the Followup Interview for 2 of the 4 categorical variables and 8 of the 16 quantitative variables. For each of the remaining categorical variables, the kappa statistic was significant (.73 and .49). For the remaining 8 quantitative variables, the intraclass correlation coefficients ranged from .750 to .999. The findings signify satisfactory interviewer reliability of the instruments. These brief instruments could easily be adapted for use in other treatment evaluation studies where brevity in data collection is considered desirable.