In the present study we evaluated the relationship between psychosocial functioning and cocaine use to address the questions (1) to what extent in-treatment cocaine use can be linked to psychosocial functioning following treatment for cocaine dependence, and (2) whether some urine measures of cocaine use more consistently predict such changes. We compared three measures of psychosocial functioning (cocaine dependence, social adjustment, and depression) and three urine toxicology measures of cocaine use (EMIT, a qualitative measure; BE, a quantitative measure; and New Uses, a qualitative measure derived from quantitative BE data). Overall, there were significant associations between psychosocial functioning and urine toxicology results, with greater cocaine use during treatment associated with poorer functioning during treatment and at study exit. Furthermore, regression analyses suggested that the three urine toxicology measures were linked to psychosocial functioning to different degrees: New Uses data from various phases of treatment appeared to be more consistently associated with clinical outcome (12 of 13 associations significant) than either EMIT (5 of 13) or BE (7 of 13). The association between in-treatment cocaine use and psychosocial functioning was particularly robust for New Uses of cocaine during the intervention and post-intervention phases and SDSS and BDI at exit (R-squared values 9−20%). The associations of SAS-SR with New Uses of cocaine were more modest (R-squared values 5−8%).
Our results suggest an affirmative answer to the question posed by Dr. Tai (1997)
on the value of urine toxicology results as predictors of changes in psychosocial functioning, i.e., there is a significant association between cocaine use as measured by urine drug screens and psychosocial functioning. This study does not address questions of causation, However, clinical investigators who wish to use urine data as primary outcome measures and regulators who must approve treatments (or approve coverage of treatment by insurance) have some assurance that urine data, at least when analyzed by New Uses criteria, do have implications for psychosocial outcome. Not surprisingly, the association between in treatment cocaine use and psychosocial functioning at exit was strongest for the post-intervention phase. This was particularly apparent for SDSS and cocaine dependence (rows 1A, 1B, an 1C in ). On this measure, the association with New Use data tended to increase across the study, with adjusted R-squares of 5, 9, and 20% in Baseline, Intervention, and Post-intervention.
Nevertheless, the amount of variance accounted for by the urine screens was relatively small, with most R-squared values less than 15% and the highest only 20%. Cocaine use assessed through urine drug screens can predict psychosocial functioning, but cannot substitute for more direct measures of psychosocial functioning.
For simply measuring differences between experimental treatment groups, EMIT and New Uses appeared nearly equal in sensitivity (significant treatment effects detected both during and after treatment), while BE appeared to be slightly less sensitive (significant treatment effects detected only after treatment). This finding suggests that EMIT data should usually be adequate to serve as the primary outcome measure in clinical trials assessing reductions in drug use; clinically significant group differences seem likely to be detected by EMIT without determination of New Uses. This conclusion is tentative because we are basing it on data from an abstinence-reinforcement intervention that had relatively robust effects. Studies of a treatment with more subtle effects might require the greater sensitivity of an outcome measure such as New Uses. What seems more clear is that BE, with its extreme variability, may be inferior to EMIT as a primary measure of group differences.
Intuitively, one might expect BE to outperform EMIT as a predictor of psychosocial functioning, if only because the quantitative nature of BE seems as if it would permit more sensitive detection of fluctuations in amount of cocaine use. EMIT, when applied to successive urine specimens taken at intervals of only a few days, can overrepresent cocaine use because multiple positives may result from a single use (i.e., “carryover positives”) if the concentration of analytes remains above the EMIT cutoff (Li et al., 1995
; Preston et al., 1997b
). Yet quantitative urinalysis using BE concentrations has drawbacks of its own, because BE urine concentrations vary widely as a function of individual variability in cocaine metabolism, fluid consumption, frequency of use and time elapsed between cocaine use and urine collection, and wide variations in last cocaine dose (Delucchi et al., 2002
; Delucchi et al., 1997
; Jufer et al., 2006
; Jufer et al., 2000
; Preston et al., 1997c
). This wide range of BE urine concentrations leads to highly variable, often poorly distributed data (Preston et al., 1997c
). Therefore, quantitative BE data may actually be more useful when converted (via the New Uses method) back to qualitative data. This is not a step backwards: qualitative data obtained from the New Uses method more accurately reflect the occurrence of cocaine use than those obtained from EMIT (Preston et al., 1997a
). In the present study, out of the 16,725 urines collected, EMIT detected 11,204 total cocaine-positive specimens, and the New Uses method identified 3,002 (27%) of those as carryover false positives. The ability of the New Uses method to eliminate false positives may account for its greater sensitivity to detect real changes in cocaine use that predict changes in psychosocial functioning.
One limitation of our study, noted above, is that we performed a large number of statistical tests without correcting the error rate. Accordingly, we have not attempted to interpret or discuss any of the outcomes of the individual associations we found. The measures of psychosocial assessment were chosen based on the original study design, not specifically for the present analyses; we selected them for these analyses because they were the most appropriate measures available. Further studies are needed to assess a wider range of psychosocial function. Another limitation is that the sample in the present study consisted primarily of heroin-dependent individuals who also had cocaine-use disorders. Most treatment-seeking cocaine abusers in the Baltimore, MD area also use illicit opiates (NIDA, 2006). Future studies should assess whether the present findings also apply to primary cocaine users. The present study showed a significant relationship between in-treatment cocaine use and psychosocial measures at study exit; future research should examine the durability of this relationship, for example during follow-up periods after treatment.
The core of the present findings lies in the overall pattern of associations, which consistently pointed to the New Uses method as the most reliable predictor of psychosocial functioning. While it is unlikely that urinalysis data could substitute for direct assessment of psychosocial functioning, the New Uses method implies more about psychosocial functioning than other urine toxicology measures do.