Comparing Refrigeration to Immediate Room Temperature Testing for Uric Acid Monitoring in Rasburicase-Treated Patients.

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Rasburicase retains activity at room temperature (RT), so specimens collected for uric acid-level monitoring require cooling protocols. Our objective was to determine if we could ease these preanalytical requirements to improve compliance while maintaining accuracy. Fifty pairs of specimens were transported and stored either on ice or at RT. All were tested at 3 time points postcollection: immediately upon arrival to the laboratory (approximately 45 min), 90, and 135 min. Uric acid concentrations are not clinically significantly different in RT or iced specimens, as long as specimens are tested within approximately 45 min postcollection. There was a negative bias in uric acid levels in a subset of specimens if they were held at RT and tested at 90 min (-9.1%) and 135 min (-17.5%). Specimens tested within 2 rasburicase half-lives postinfusion have an additional 24% decrease in uric acid levels if kept at RT for 90 min. Specimens from patients given a 6 mg dose had an 18% decrease in uric acid concentration compared to a 3 mg dose. Laboratories that can test uric acid levels rapidly after specimen collection may be able to validate alternative preanalytical methods to transporting and testing on ice.