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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.