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Factors influencing naproxen metabolite interference in total bilirubin assays

Nabiha Huq Saifee1, Pratistha Ranjitkar1, Dina N Greene1

  • 1Department of Laboratory Medicine, University of Washington, 1959 NE Pacific St, Box 357110, Seattle, WA 98195, USA.

Clinical Biochemistry
|November 22, 2015
PubMed
Abstract

Insights

Naproxen metabolite O-desmethylnaproxen (ODMN) interferes with some total bilirubin (Tbil) assays due to acidic pH. The AU Jendrassik and Grof (JG) Tbil assay is reliable for measuring Tbil during naproxen overdose.

Area of Science:

  • Clinical Chemistry
  • Analytical Chemistry
  • Pharmacology

Background:

  • Naproxen metabolite O-desmethylnaproxen (ODMN) causes interference in certain total bilirubin (Tbil) assays.
  • The reasons for ODMN interference in Jendrassik and Grof (JG) Tbil assays and its absence in direct bilirubin (Dbil) assays remain unclear.

Purpose of the Study:

  • To elucidate the conditions responsible for the interference pattern of ODMN in bilirubin assays.
  • To identify reliable methods for Tbil measurement in patients taking naproxen.

Main Methods:

  • Plasma samples spiked with ODMN and naproxen were analyzed on Beckman Coulter DxC and AU instruments.
  • Absorbance spectra were recorded for ODMN with Dbil and Tbil assay reagents at varying pH levels.

Main Results:

  • ODMN caused positive interference in DxC JG Tbil assays but not in AU Tbil or Dbil assays, or DxC Dbil assays.
  • Neutralizing acidic pH in Dbil reagents enabled ODMN reaction with diazo salts.
  • Spectra showed ODMN diazo-reacted products absorb maximally between 400-560nm, with DxC JG Tbil assay's 520nm monitoring wavelength being closer to the peak than AU Tbil's 570/660nm.

Conclusions:

  • Acidic pH in diazo-based Dbil assays prevents ODMN reaction.
  • The AU JG Tbil assay is a dependable method for Tbil determination in naproxen overdose cases.
Keywords:
AUBilirubinDxCInterferenceNaproxenO-desmethylnaproxenSpectrophotometry

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