Sterling McPherson

Missing Data in Substance Abuse Treatment Research: Current Methods and Modern Approaches

Two common procedures for the treatment of missing information, listwise deletion and positive urine analysis (UA) imputation (e.g., if the participant fails to provide urine for analysis, then score the UA positive), may result in significant biases during the interpretation of treatment effects. To compare these approaches and to offer a possible alternative, these two procedures were compared to the multiple imputation (MI) procedure with publicly available data from a recent clinical trial. Listwise deletion, single imputation (i.e., positive UA imputation), and MI missing data procedures were used to comparatively examine the effect of two different buprenorphine/naloxone tapering schedules (7- or 28-days) for opioid addiction on the likelihood of a positive UA (Clinical Trial Network 0003; Ling et al., 2009). The listwise deletion of missing data resulted in a nonsignificant effect for the taper while the positive UA imputation procedure resulted in a significant effect, replicating the original findings by Ling et al. (2009). Although the MI procedure also resulted in a significant effect, the effect size was meaningfully smaller and the standard errors meaningfully larger when compared to the positive UA procedure. This study demonstrates that the researcher can obtain markedly different results depending on how the missing data are handled. Missing data theory suggests that listwise deletion and single imputation procedures should not be used to account for missing information, and that MI has advantages with respect to internal and external validity when the assumption of missing at random can be reasonably supported.

Measurement Invariance of the Perceived Stress Scale and Latent Mean Differences across Gender and Time

Measurement invariance of the 2-factor model of the Perceived Stress Scale--10-item version (Cohen & Williamson, 1988) was tested across men and women at two time points and in the combined total sample over a 2-year time frame (n = 871). Measurement invariance results indicated that the scale measured the latent factors, stress and counter-stress, equivalently in men and women and over time. With measurement invariance demonstrated, differences in latent means were tested. Results indicated that men had lower levels of frequencies of stressors, and at one time point, higher levels of counter-stress, when compared with women. When examining change in frequencies of stressors and counter-stress over 2 years with the combined male and female sample, stressors remained stable, yet counter-stress increased over time. These findings may aid in the interpretation of results when examining stressors and counter-stress in clinical samples where one would expect stress to increase, whereas positive psychological states decrease.

Duration Effects in Contingency Management Treatment of Methamphetamine Disorders

The primary aim of this study was to determine whether different durations of contingency management (CM) in conjunction with psychosocial treatment produced different rates of abstinence among methamphetamine dependent individuals. Participants were randomized to one of the four 16-week treatment conditions: standard psychosocial treatment or psychosocial treatment plus one of the three durations of CM (one-month, two-month, or four-month). A total of 118 participants were randomized to the four treatment conditions. There were significant differences across treatment conditions for number of consecutive days of methamphetamine abstinence (p<0.05). These differences were in the hypothesized direction, as participants were more likely to remain abstinent through the 16-week trial as CM duration increased. A significant effect of treatment condition (p<0.05) and time (p<0.05) on abstinence over time was also found. Longer durations of CM were more effective for maintaining methamphetamine abstinence.

Voucher-Based Reinforcement for Alcohol Abstinence Using the Ethyl-Glucuronide Alcohol Biomarker.

This study assessed the effects of a contingency management (CM) intervention for alcohol consumption in 10 alcohol-dependent participants. An ABCA design was used. Vouchers were provided contingent on results of ethyl glucuronide (EtG) urine tests (an alcohol biomarker with a 2-day detection period) and alcohol breath tests during the C phase. The percentage of negative urines was 35% during the first baseline phase, 69% during the C phase, and 20% during the return-to-baseline phase. Results suggest that EtG urine tests may be a feasible method to deliver CM to promote alcohol abstinence.

Investigating reinforcer magnitude and reinforcer delay: a contingency management analog study.

The influence of reinforcer magnitude and reinforcer delay on smoking abstinence was studied using an analog model of contingency management. Participants (N = 103, 74% men) visited our laboratory 3 times daily for 5 days and received money for providing a breath sample that indicated smoking abstinence (carbon monoxide level ≤6 parts per million). Using a factorial design, we assigned participants randomly to 1 of 4 groups that could earn a total of either

High levels of agreement between clinic-based ethyl glucuronide (EtG) immunoassays and laboratory-based mass spectrometry

207.50 (high-magnitude condition) or

Sanctity of marriage and marital quality

70.00 (low-magnitude condition), and received earnings either at each visit (no-delay condition) or in a single lump sum 1 week following the study (delay condition). High-magnitude reinforcement, regardless of delay, was associated with higher rates of abstinence than was low-magnitude reinforcement. High magnitude of reinforcement provided immediately but in incremental amounts was associated with longer intervals to relapse during treatment in comparison with high-magnitude reinforcement provided in a single lump sum after a delay. Low rates of responding in the low-magnitude conditions made interpretation of the impact of delay in those conditions difficult. These findings further demonstrate that high magnitude of reinforcement results in better outcomes than does low magnitude of reinforcement, and that a delay to reinforcement can be detrimental-even when a high magnitude of reinforcement is provided.

Biochemical Marker of Use Is a Better Predictor of Outcomes Than Self‐Report Metrics in a Contingency Management Smoking Cessation Analog Study

Abstract Background: Immunoassay urine drug screening cups that detect use for two or more days are commonly used in addiction treatment settings. Until recently, there has been no comparable immunoassay test for alcohol use in these settings. Objectives: The aim of this study was to assess the agreement of a commercially available ethyl glucuronide immunoassay (EtG-I) test conducted at an outpatient addiction clinic and lab-based EtG mass spectrometry (EtG-MS) conducted at a drug testing laboratory at three cut-off levels. High agreement between these two measures would support the usefulness of EtG-I as a clinical tool for monitoring alcohol use. Methods: Forty adults with co-occurring alcohol dependence and serious mental illnesses submitted 1068 urine samples over a 16-week alcohol treatment study. All samples were tested using EtG-I on a benchtop analyzer and 149 were randomly selected for EtG-MS analysis at a local laboratory. Agreement was defined as the number of samples where EtG-I and EtG-MS were both above or below a specific cut-off level. Agreement was calculated at low cut-off levels (100 and 250 ng/ml), as well as at a higher cut-off level (500 ng/ml) recommended by most by commercial drug testing laboratories. Results: Agreement between EtG-I and EtG-MS was high across all cut-off levels (90.6% at 100 ng/ml, and 96.6% at 250 and 500 ng/ml). Conclusions: EtG immunoassays conducted at low cut-off levels in point-of-care testing settings have high agreement with lab-based EtG-MS. EtG-I can be considered a useful clinical monitoring tool for alcohol use in community-based addiction treatment settings.

A ‘missing not at random’ (MNAR) and ‘missing at random’ (MAR) growth model comparison with a buprenorphine/naloxone clinical trial

Mahoney and colleagues’ theorizing about the potential role of sanctity as a central feature of religion/spirituality is invoked to examine the relationships among sanctity of marriage, (un)forgiveness, sacrifice, and both positive and negative marital satisfaction. The study examined the perspectives of both members of 342 marital dyads using an Actor–Partner Interdependence Model and a multilevel path modeling. The results indicate that sanctity is related positively to marital satisfaction and negatively to martial dissatisfaction. Sanctity emerged as a strong predictor of marital quality even after accounting for forgiveness, unforgiveness, and sacrifice. Though sanctity is directly linked to positive marital satisfaction, the mediation effects via (un)forgiveness were not significant; however, a mediation effect via sacrifice was significant, which was related to negative marital quality.

Young adult waterpipe smokers: Smoking behaviors and associated subjective and physiological effects.

BACKGROUND AND OBJECTIVES This investigation compared cotinine (primary metabolite of nicotine) at study intake to self-report metrics (e.g., Fagerstrom Test of Nicotine Dependence [FTND]) and assessed their relative ability to predict smoking outcomes. METHODS We used data from an analog model of contingency management for cigarette smoking. Non-treatment seeking participants (N = 103) could earn money in exchange for provision of a negative carbon monoxide (CO) sample indicating smoking abstinence, but were otherwise not motivated to quit. We used intake cotinine, FTND, percent of friends who smoke, and years smoked to predict longitudinal CO and attendance, time-to-first positive CO submission, and additional cross-sectional outcomes. RESULTS Intake cotinine was consistently predictive (p < .05) of all outcomes (e.g., longitudinal CO and attendance, 100% abstinence, time-to-first positive CO sample), while years smoked was the only self-report metric that demonstrated any predictive ability. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE Cotinine could be more informative for tailoring behavioral treatments compared to self-report measures.