Diagnostic accuracy for self-reported methamphetamine use versus oral fluid test as the reference standard in a methamphetamine-dependent intervention trial population.

Gregory Carter, Matthew J Spittal, Linda Glowacki, Dimitri Gerostamoulos, Paul Dietze, Barbara Sinclair, Shalini Arunogiri, Michael Berk, Dan I Lubman, Victoria Manning, Peter Higgs, Brendan Quinn, Amanda Baker, Olivia M Dean, Alyna Turner, Rebecca McKetin

Journal: Addiction (Abingdon, England) 2023;118(3):470-479

PMID: 36367075

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Abstract

AIMS

Treatment of methamphetamine dependence requires monitoring of recent use or abstinence. Self-report is commonly used for routine monitoring, but the accuracy of self-report is not established. For the treating clinician, the key accuracy statistic is the negative predictive value (NPV). The study aim was to estimate the NPV of self-reported non-use of methamphetamine compared with an oral fluid reference standard.

DESIGN, SETTING AND PARTICIPANTS

This study was a secondary (subgroup) analysis from a randomized controlled pharmacotherapy trial. Three Australian outpatient addiction services took part. Particpants were 139 people dependent on methamphetamine.

MEASUREMENTS

Weekly oral fluid samples over 12 weeks to determine methamphetamine (and amphetamine) concentrations were used as the reference standard. Self-report of any methamphetamine use in the previous 7 days by the time-line follow-back method was the index test. Standard diagnostic accuracy statistics were calculated for all available paired episodes (n = 1134). Three NPV values were calculated: unadjusted NPV and NPV adjusted for clustering of observations through logistic regression and generalized estimating equation (GEE). We also calculated the NPVs for a range of prevalence rates of methamphetamine use, for the calculated levels of sensitivity and specificity.

FINDINGS

Sensitivity was 96.4% [95% confidence interval (CI) = 95-97.5], specificity was 63.7% (95% CI = 57.3-69.8) and positive predictive value (PPV) was 90.8% (95% CI = 88.8-92.6). The unadjusted NPV was 82.7% (95% CI = 76.5-87.9), adjusted NPV by logistic regression 82.7% (95% CI = 73.9-91.5) and GEE 76.8% (95% CI = 66.8-86.8). At a methamphetamine use prevalence of 5%, the estimated NPV would be 99.7% (95% CI = 99.6-99.9) and at 95% prevalence, 48.2% (95% CI = 39.6-57.0).

CONCLUSIONS

Self-report of no recent methamphetamine use appears to be sufficiently accurate to be clinically useful at the expected prevalence rates of methamphetamine use in clinical treatment settings. If generalizable to clinical settings, where these tests are routinely conducted, this may permit a reduction in the frequency and cost of oral fluid assays.

Address: College of Health, Medicine and Wellbeing, School of Medicine and Public Health, University of Newcastle, Callaghan, Australia.; Melbourne School of Population and Global Health, University of Melbourne, Australia.; Victorian Institute of Forensic Medicine, Southbank, Victoria, Australia.; Behaviours and Health Risks Program, Burnet Institute, Melbourne, Australia.; National Drug Research Institute and enable Institute, Curtin University, Melbourne, Australia.; Graduate School of Medicine, University of Wollongong, Australia.; Monash Addiction Research Centre, Eastern Health Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Australia.; Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia.; Florey Institute for Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia.; Turning Point, Eastern Health, Richmond, Australia.; Monash Addiction Research Centre, Eastern Health Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Australia.; Turning Point, Eastern Health, Richmond, Australia.; Behaviours and Health Risks Program, Burnet Institute, Melbourne, Australia.; Department of Public Health, La Trobe University, Bundoora, Australia.; Behaviours and Health Risks Program, Burnet Institute, Melbourne, Australia.; Australian Institute of Family Studies, Melbourne, Australia.; Deakin University, IMPACT - the Institute for Mental and Physical Health and Clinical Translation, School of Medicine, Barwon Health, Geelong, Australia.; National Drug and Alcohol Research Centre, UNSW, Sydney, Australia.

DOI: 10.1111/add.16085

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MeSH Terms: Humans, Methamphetamine, Self Report, Australia, Amphetamine, Sensitivity and Specificity, Reference Standards