False-positive acetaminophen results in a hyperbilirubinemic patient.
BACKGROUND
Acetaminophen was falsely detected in the plasma of a severely jaundiced patient, and a methodologic interference from bilirubin was suspected.


METHODS
Acetaminophen was measured by an enzymatic method (GDS Diagnostics). The putative bilirubin interference was investigated in 12 hyperbilirubinemic specimens and in bilirubin linearity calibrators. The analytical method was modified to correct for background absorbance at a second wavelength. Hyperbilirubinemic specimens were fortified with acetaminophen to assess the effect of the interference on acetaminophen measurements.


RESULTS
Acetaminophen was detected in 12 specimens from hyperbilirubinemic patients without a history of recent acetaminophen exposure. Dilution of hyperbilirubinemic specimens produced a nonproportional decrease in apparent acetaminophen concentrations, and no acetaminophen was detected when bilirubin was <50 mg/L. Background correction at a second wavelength failed to compensate for the interference. Although erroneous acetaminophen concentrations were detected in all specimens with high bilirubin, acetaminophen measurements in fortified specimens were accurate.


CONCLUSIONS
The data are consistent with bilirubin interference in the enzymatic and/or chromogenic reactions involved in the acetaminophen method.
Bertholf
Roger L
RL
Department of Pathology, University of Florida Health Science Center/Jacksonville, 32209, USA. roger.bertholf@jax.ufl.edu
Johannsen
Laura M
LM
Bazooband
Alireza
A
Mansouri
Vafa
V
D000082:Acetaminophen / Q000097:blood*; D000293:Adolescent; D001663:Bilirubin / Q000032:analysis*; D005189:False Positive Reactions; D006801:Humans; D006932:Hyperbilirubinemia / Q000097:blood*; D007565:Jaundice / Q000097:blood; D008297:Male
D000082:Acetaminophen; D001663:Bilirubin