N-acetylcysteine interference of Trinder-based assays.
OBJECTIVE
The primary objective of this study was to evaluate potential interference of Trinder-based chemistry assays by N-acetylcysteine (NAC). A secondary objective was to look for evidence of interference in patients treated with NAC for acetaminophen (APAP) overdose.


METHODS
Dilutions of NAC in plasma were tested for interference using the following Roche Diagnostics Trinder-based assays on a cobas 8000 system: enzymatic creatinine (Cr), cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), triglycerides (TRIG), and uric acid (UA). Two non-Trinder Roche assays - urea nitrogen (BUN) and glucose (GLUC) - were tested as controls. Sekisui N-geneous® low-density lipoprotein cholesterol (LDL-C) reagent was also evaluated. Retrospective chart review of APAP overdose cases over 49months was conducted to look for differences in plasma Cr before and after intravenous (IV) NAC administration.


RESULTS
NAC concentrations (shown in parentheses) that caused ≥10% inhibition for individual assays were (in order of sensitivity to interference): TRIG (570mg/L)>CHOL (740mg/L)≈Cr (790mg/L)>UA (1100mg/L)>HDL-C (1760mg/L)>LDL-C (2900mg/L). Neither BUN nor GLUC achieved significant inhibition up to 10,000mg/L NAC. Evidence for relatively minor inhibition of Cr was observed in patients after NAC administration.


CONCLUSIONS
NAC inhibition of the assays investigated typically occurs at concentrations higher than expected during IV and oral NAC therapy.
ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, 500 Chipeta Way, Salt Lake City, UT 84108, USA; Department of Pathology, University of Utah, Salt lake City, UT, 500 Chipeta Way, Salt Lake City, UT 84108, USA. Electronic address: jonathan.genzen@path.utah.edu.
Jonathan R
JR
Genzen
ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, 500 Chipeta Way, Salt Lake City, UT 84108, USA.
Joshua J
JJ
Hunsaker
Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA, 200 Hawkins Drive, Iowa City, IA 52242, USA.
Louis S
LS
Nelson
Department of Emergency Medicine, University of Iowa Hospitals and Clinics, Iowa City, IA, 200 Hawkins Drive, Iowa City, IA 52242, USA.
Brett A
BA
Faine
Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA, 200 Hawkins Drive, Iowa City, IA 52242, USA.
Matthew D
MD
Krasowski
D000082:Acetaminophen / Q000506:poisoning*; D000111:Acetylcysteine / Q000097:blood / Q000627:therapeutic use*; D005290:Ferric Compounds / Q000737:chemistry*; D006801:Humans; D011041:Poisoning / Q000188:drug therapy; D012189:Retrospective Studies
D005290:Ferric Compounds; D000082:Acetaminophen; C009585:Trinder's reagent; D000111:Acetylcysteine
Acetaminophen; Interference; N-acetylcysteine; Overdose; Paracetamol; Toxicity; Trinder reaction