Does low urine creatinine level indicate the presence of urine alcohol in methadone maintenance treatment patients?
OBJECTIVE
We sought to test the assumption that a low urine creatinine level is indicative of the presence of alcohol in the urine of patients prescribed methadone.


METHODS
This is a medical record review of 261,055 urine samples from approximately 6,000 patients prescribed methadone during a one-year period and for whom both urine creatinine and ethanol levels were simultaneously measured. We defined a creatinine level of less than 2.26 mmol/L as 'low' used a urine ethanol level of greater than 2.0 mmol/L as the reference standard for alcohol consumption.


RESULTS
The sensitivity and specificity of low urine creatinine as a marker for the detection of urine ethanol are 11.9% (95% CI: 11.3, 12.5%) and 96.7% (95% CI: 96.7, 96.7%), respectively. In this patient population with a low (3.6%) prevalence of alcohol in the urine, the results correspond to a positive predictive value of 11.9% (95% CI: 11.3, 12.6%) and a negative predictive value of 96.7% (95% CI: 96.7, 96.7%), respectively.


CONCLUSIONS
Low urine creatinine is a poor screening test for detecting alcohol consumption among patients on methadone. However, a normal creatinine level has a 96.7% probability of no alcohol urine present in the urine.
Ontario Addiction Treatment Centres, Richmond Hill, Ontario, Canada.
Michael
M
Varenbut
Carolyn J
CJ
Plater-Zyberk
Andrew
A
Worster
Jeff
J
Daiter
D000701:Analgesics, Opioid; D054316:Biomarkers, Pharmacological / Q000652:urine; D003404:Creatinine / Q000652:urine*; D000431:Ethanol / Q000652:urine*; D006801:Humans; D008499:Medical Records; D008691:Methadone / Q000627:therapeutic use*; D009864:Ontario; D009293:Opioid-Related Disorders / Q000534:rehabilitation*; D012680:Sensitivity and Specificity; D015813:Substance Abuse Detection
D000701:Analgesics, Opioid; D054316:Biomarkers, Pharmacological; D000431:Ethanol; D003404:Creatinine; D008691:Methadone