Table 3. Performance of Predictive Models for Opioid Return to Use.
| LASSO model, coefficienta | Logistic models on training set, OR (95% CI)b | ||||
|---|---|---|---|---|---|
| (1) Treatment entry predictors only | (2) Treatment entry predictors and opioid use first 3 wk | (A) Treatment entry variables | (B) Opioid use first 3 wk | (C) Treatment entry variables, opioid use first 3 wk | |
| Treatment entry | |||||
| Heroin use (0-28 d) | 0.0223 | 0.0151 | 1.02 (1.01-1.04) | NA | 1.02 (1.00-1.03) |
| Positive UDS result for morphine | 0.2645 | NA | 1.54 (1.19-2.00) | NA | 1.03 (0.76-1.38) |
| Heroin injection | 0.0505 | NA | 1.28 (0.98-1.67) | NA | 1.13 (0.82-1.56) |
| Positive UDS result for cocaine | 0.2763 | 0.0687 | 1.64 (1.26-2.14) | NA | 1.25 (0.91-1.71) |
| Week 1: negative (reference) | |||||
| Positive | NA | 0.4894 | NA | 3.72 (2.59-5.36) | 3.34 (2.30-4.83) |
| Missing | NA | 0.5202 | NA | 3.81 (2.71-5.37) | 3.50 (2.47-4.95) |
| Week 2: negative (reference) | |||||
| Positive | NA | 0.8396 | NA | 3.58 (2.57-4.99) | 3.34 (2.39-4.66) |
| Missing | NA | 1.2467 | NA | 7.18 (5.04-10.21) | 6.87 (4.83-9.79) |
| Week 3: negative (reference) | |||||
| Positive | NA | 1.0226 | NA | 4.36 (3.11-6.09) | 4.13 (2.94-5.81) |
| Missing | NA | 1.4181 | NA | 8.31 (5.94-11.63) | 7.72 (5.51-10.83) |
| Log likelihood (df) | NA | NA | −1062.10 (6) | −781.52 (9) | −772.18 (13) |
| Likelihood ratio test with model C | NA | NA | χ27 = 579.84 | χ211 = 18.68 | NA |
| χ2 P value | NA | NA | <.001 | .002 | NA |
| AUROC (95% CI) on testing setsc | 0.67 (0.62-0.71) | 0.81 (0.77-0.85) | 0.68 (0.63-0.72) | 0.82 (0.78-0.85) | 0.82 (0.78-0.85) |
Abbreviations: AUROC, area under the receiver operating characteristic curve; LASSO, least absolute shrinkage and selection operator; NA, not applicable; OR, odds ratio; UDS, urine drug screen.
Model coefficients were derived from the training set only. Predictive performance of the models was estimated with the AUROC using the testing set. Thirty-seven participants were excluded for the following reasons: missing any information on timeline follow-back (TLFB), UDS, heroin injection, withdrawal, nicotine dependence, and physical and mental condition.
Three participants were excluded for missing information on TLFB or heroin injection; treatment site was treated as a random effect in the logistic regression model.
Training AUROC and details of fitting the LASSO model are provided in the eMethods in Supplement 1. Effects of UDSs missing or positive were assumed additive across weeks, including 1 additional parameter for all 3 weeks with negative results.