Urine fluorescence using a wood's lamp to detect the antifreeze additive sodium fluorescein: A qualitative adjunctive test in suspected ethylene glycol ingestions

Antifreeze ingestions require rapid and accurate differential diagnosis to prevent fatal outcomes. Sodium fluorescein is added to some commercial antifreeze preparations (ethylene glycol) to a final concentration of ∼20 μg/mL as a colorant to aid in detection of automobile cooling-system leaks. For an adult human being, a potentially toxic volume of antifreeze is 30 mL, which contains 0.4 to 0.6 mg sodium fluorescein. Six male volunteers were given a 0.6-mg oral bolus of sodium fluorescein on an empty stomach. Urine was collected at two-hour intervals. Using a Wood's lamp, visually detectable fluorescence was seen with 100% reliability for two hours and 60% reliability for four hours. A second group of male volunteers was given the same dose of sodium fluorescein, and fluorescence was measured with a fluorometer during a six-hour period. Detectable fluorescence was present in all samples except the zero time point, including those with no fluorescence present by visual examination. We conclude that exposing urine to a Wood's lamp may be a useful adjunctive diagnostic test for early evaluation of patients with suspected antifreeze ingestion while awaiting definitive quantitative analysis of serum ethylene glycol concentration. A prospective clinical trial is needed to evaluate the frequency of false-positives and false-negatives.