Purpose: The present study examines the relationship between
the dose of acetaminophen reported to have been ingested by patients and the
occurrence of serum acetaminophen levels above the ‘possible toxicity’ line in
patients presenting at the hospital after acetaminophen overdose. The
prognostic value of patient-reported dosage cut-offs of 8, 10 and 12 g was
determined.
Methods: This retrospective cohort study included patients admitted to the
emergency department or hospital within 24 hours of acetaminophen ingestion.
Serum acetaminophen concentrations were considered to be the gold standard, and
specificity, sensitivity and positive/negative predictive values were calculated
from the reported ingested dose, to predict toxicity using the Rumack–Matthew
nomogram (i.e. the ‘possible toxicity’ treatment line) and standard equations.
Results Of 305 patients identified, 291 met the study inclusion criteria, and
121 (41.6%) had serum acetaminophen concentrations above the ‘possible
toxicity’ treatment line. The range of patient-reported acetaminophen ingested
was 1–75 g, with 185 patients (63.6%) reporting ≥8 g. One hundred eighteen
patients (97.5%) who reported ingesting ≥8 g had serum acetaminophen
concentrations above the ‘150-line’, compared with only three patients (2.5%)
who reported ingesting <8 g (p < 0.001). The positive
predictive value of a patient-reported dose ≥8 g for predicting serum
acetaminophen concentrations above the ‘possible toxicity’ treatment line was
63.78%, with a negative predictive value of 97.17%. The sensitivity of
patient-reported doses ≥8 g was high (97.52%) but with low specificity
(60.59%). The sensitivity of patient-reported doses ≥10 g also was high
(89.26%) with low specificity (65.29%), whereas the sensitivity of ≥12 g dose
was low (61.16%) with high specificity (86.47%).
Conclusions: Patient-reported doses of
acetaminophen are good risk indicators for acetaminophen overdose patients in
Malaysia. Patient-reported ingestion of ≥8 g (as a cut-off dose) had a higher
sensitivity than ≥10 g or ≥12 g. The results of this study have important
implications for toxicity risk evaluations in areas with poor serum
acetaminophen assay availability.
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