Objective This secondary analysis of data from a randomized controlled trial tested two behavioral economics mechanisms (substitutability and delay discounting) to explain outcomes using contingency management (CM) for methamphetamine dependence. Frequency and purchase type (hedonic/utilitarian and consumable/durable) of CM payments were also examined. Methods 82 methamphetamine-dependent gay/bisexual men randomly assigned to conditions delivering CM received monetary vouchers in exchange for stimulant-negative urine samples in a 16-week trial requiring thrice weekly visits (Shoptaw et al., 2005). At any visit participants could redeem vouchers for goods. A time-lagged counting process Cox Proportional Hazards model for recurrent event survival analysis examined aspects of the frequency and type of these CM purchases. Results After controlling for severity of baseline methamphetamine use and accumulated CM wealth, as measured by cumulative successful earning days, participants who redeemed CM earnings at any visit (“spenders”) were significantly more likely to produce stimulant-negative urine samples in the subsequent visit, compared to those who did not redeem (“savers”) 1.011* [1.005, 1.017], Z=3.43, p<0.001. Conclusions Findings support the economic concept of substitutability of CM purchases and explain trial outcomes as a function of frequency of CM purchases rather than frequency or accumulated total CM earnings. Promotion of frequent purchases in incentive-based programs should facilitate substitution for the perceived value of methamphetamine and improve abstinence outcomes.

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Decision-making tendencies and spending within cash voucher-based interventions have individually beenshown to be related to future abstinence among participants with methamphetamine use disorder (MUD), but less is known of their independent contributions. This study of participants in a contingency management (CM) trial investigated whether decision-making and spending were each associated with future abstinence. Thirty-two outpatients with MUD, predominately male (68%) and mixed ancestry (94%) with a median age of 34 years, participated in an 8-week cash voucher-based CM pilot trial. Prior to commencing the trial, participants completed a computerized Iowa Gambling Task (IGT) to measure decision-making preferences for more frequent rewards and longer term gains of greater magnitude. Spending and abstinence of participants were tracked over the duration of the trial. In a secondary analysis, time-lagged counting process Cox Proportional Hazard models were conducted. Baseline decision-making, characterized by a preference for frequent rewards, was associated with a greater likelihood of future spending, Hazard Ratio; HR = 1.13 [1.06: 1.21]. Avoidance of short-term rewards to realize longer term, higher magnitude rewards, and spending at the prior visit were each associated with abstinence on the trial,

The objective of this study was to measure HIV screening rates and variables associated with screening among new enrollees in California's Low Income Health Program (LIHP). A logit model was used to estimate associations between HIV screening and enrollment, claims, and encounter data for enrollees. HIV prevalence among new LIHP enrollees was 1.2%. Among 42,550 new LIHP enrollees with no prior HIV diagnosis, only 27% received screening within 12 months of their first medical evaluation. A total of 350 new HIV diagnoses were identified (incidence rate of 0.8%), exceeding the 0.1% level at which the Centers for Disease Control and Prevention (CDC) recommends routine HIV screening. California reduced screening barriers by removing required written informed consent and pretest counseling; the Affordable Care Act (ACA) eliminated cost-sharing and enhanced access. Removing financial and administrative barriers to HIV screening is necessary, but may be insufficient to reach CDC's recommended screening targets.