Biomaterial Database

Mechanism and elimination of aspirin-induced interference in Emit II d.a.u. assays. 1994

M W Linder, and R Valdes

Department of Pathology, University of Louisville School of Medicine, University of Louisville Hospital, KY 40292.

The presence of salicylates in urine reduces the signal in Emit assays (Syva), potentially yielding false-negative drugs-of-abuse screening results. We demonstrate that the principal urinary metabolite of salicylate, salicyluric acid (SUA; 2-hydroxybenzoylaminoacetic acid), interferes with the measurement of NADH formed in the assay by reducing the molar absorptivity of NADH at 340 nm. Thus, for a given concentration of d.a.u. analyte the change in absorbance over the assay time interval is less in the presence of SUA. With the Emit cocaine assay on the Hitachi 704 analyzer, the rate of absorbance change (delta AR) monitored at 340 nm for a specimen containing approximately 270 micrograms/L benzoylecgonine (BE) was 57 +/- 1.9 mA/min without SUA and 29 +/- 2.7 mA/min with 5 g/L SUA (n = 20). In contrast, delta AR determined at 376 nm was 18.6 +/- 0.5 mA/min with and 17.9 +/- 0.8 mA/min without 5 g/L SUA (n = 20). Measuring the Emit assay signal at wavelengths where SUA has no absorbance (376 nm) eliminates the interference due to SUA while maintaining the precision of the assay near the cutoff concentration for BE (300 micrograms/L).

UI	MeSH Term	Description	Entries
D009243	NAD	A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)	Coenzyme I,DPN,Diphosphopyridine Nucleotide,Nadide,Nicotinamide-Adenine Dinucleotide,Dihydronicotinamide Adenine Dinucleotide,NADH,Adenine Dinucleotide, Dihydronicotinamide,Dinucleotide, Dihydronicotinamide Adenine,Dinucleotide, Nicotinamide-Adenine,Nicotinamide Adenine Dinucleotide,Nucleotide, Diphosphopyridine
D003042	Cocaine	An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.	Cocaine HCl,Cocaine Hydrochloride,HCl, Cocaine,Hydrochloride, Cocaine
D005188	False Negative Reactions	Negative test results in subjects who possess the attribute for which the test is conducted. The labeling of diseased persons as healthy when screening in the detection of disease. (Last, A Dictionary of Epidemiology, 2d ed)	False Negative Reaction,Reaction, False Negative,Reactions, False Negative
D005954	Glucosephosphate Dehydrogenase		Glucose-6-Phosphate Dehydrogenase,Dehydrogenase, Glucose-6-Phosphate,Dehydrogenase, Glucosephosphate,Glucose 6 Phosphate Dehydrogenase
D006626	Hippurates	Salts and esters of hippuric acid.
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D001241	Aspirin	The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. (From Martindale, The Extra Pharmacopoeia, 30th ed, p5)	Acetylsalicylic Acid,2-(Acetyloxy)benzoic Acid,Acetysal,Acylpyrin,Aloxiprimum,Colfarit,Dispril,Easprin,Ecotrin,Endosprin,Magnecyl,Micristin,Polopirin,Polopiryna,Solprin,Solupsan,Zorprin,Acid, Acetylsalicylic
D012680	Sensitivity and Specificity	Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)	Specificity,Sensitivity,Specificity and Sensitivity
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D015813	Substance Abuse Detection	Detection of drugs that have been abused, overused, or misused, including legal and illegal drugs. Urine screening is the usual method of detection.	Drug Abuse Testing,Illicit Drug Testing,Street Drug Testing,Substance Abuse Testing,Drug Abuse Detection,Drug Abuse Screening,Illicit Drug Detection,Street Drug Detection,Detection, Drug Abuse,Detection, Illicit Drug,Detection, Street Drug,Detection, Substance Abuse,Detections, Drug Abuse,Detections, Illicit Drug,Detections, Street Drug,Detections, Substance Abuse,Drug Abuse Detections,Drug Abuse Screenings,Drug Abuse Testings,Drug Testing, Illicit,Drug Testings, Illicit,Illicit Drug Detections,Illicit Drug Testings,Screening, Drug Abuse,Screenings, Drug Abuse,Street Drug Detections,Street Drug Testings,Substance Abuse Detections,Substance Abuse Testings,Testing, Drug Abuse,Testing, Illicit Drug,Testing, Street Drug,Testing, Substance Abuse,Testings, Drug Abuse,Testings, Illicit Drug,Testings, Street Drug,Testings, Substance Abuse