Faculty Collaboration Database

Analytic performance of immunoassays for drugs of abuse below established cutoff values. Clin Chem 2004 Apr;50(4):717-22

Date

02/07/2004

Pubmed ID

14764642

DOI

10.1373/clinchem.2003.028878

Scopus ID

2-s2.0-1842556155 (requires institutional sign-in at Scopus site)   47 Citations

Abstract

BACKGROUND: The analytic performance and accuracy of drug detection below Substance Abuse and Mental Health Services Administration (SAMHSA) cutoffs is not well known. In some patient populations, clinically significant concentrations of abused drugs in urine may not be detected when current SAMHSA cutoffs are used. Our objectives were to define the precision profiles of three immunoassay systems for drugs of abuse and to evaluate the accuracy of testing at concentrations at which the CV was <20%.

METHODS: Drug-free urine was supplemented with analytes to assess the precision in three commercial drugs-of-abuse immunoassay systems below the SAMHSA-dictated cutoffs for amphetamines, opiates, benzoylecgonine, phencyclidine, and cannabinoids. Consecutive urine samples with signals associated with a CV <20% by Emit immunoassay and below SAMHSA cutoffs were then subjected to confirmatory analysis.

RESULTS: The CV of all immunoassay systems tested remained <20% to drug concentrations well below SAMHSA cutoffs. The accuracy of urine drug-screening results between the SAMHSA-specified cutoffs and the precision-based cutoffs was less than accuracy for specimens above the SAMHSA cutoffs, but the use of the precision-based cutoff produced a 15.6% increase in the number of screen-positive specimens and a 7.8% increase in the detection of specimens that yielded positive results on confirmatory testing.

CONCLUSION: The precision of three commercial immunoassay systems for drugs-of-abuse screening is adequate to detect drugs below SAMHSA cutoffs. Knowledge of the positive predictive values of screening immunoassays at lower cutoff concentrations could enable efficient use of confirmatory testing resources and improved detection of illicit drug use.

Author List

Luzzi VI, Saunders AN, Koenig JW, Turk J, Lo SF, Garg UC, Dietzen DJ

Author

Stanley F. Lo PhD Professor in the Pathology and Laboratory Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Cocaine
Dextroamphetamine
Dronabinol
Gas Chromatography-Mass Spectrometry
Humans
Immunoassay
Morphine
Narcotics
Phencyclidine
Predictive Value of Tests
Sensitivity and Specificity
Substance Abuse Detection