Refrigeration is not necessary for measurement of uric acid in patients treated with rasburicase.
BACKGROUND
Rasburicase, used for hyperuricemia of tumor lysis syndrome, retains activity at room temperature (RT) in in vitro studies. Cold-temperature handling is recommended for uric acid measurements in patients receiving rasburicase: collection in prechilled tubes, transportation on ice, and 4°C centrifugation. We performed a prospective study of these requirements.


METHODS
A total of 65 pairs of blood samples were collected from 34 patients, 12-24 h after receiving rasburicase. The effect of temperature on uric acid concentration was tested on paired samples handled either at RT or when cold: centrifugation (18 sample pairs), collection tube (14 pairs), transportation (24 pairs), and nine pairs were retested after 1 h at RT.


RESULTS
No significant temperature effect was seen on the uric acid measurements for any of the cold-handling steps: proportional, absolute biases were -1.4%, -0.06 mg/dL (centrifugation), -1.5%, +0.02 mg/dL (tube temperature), and -2.2%, -0.01 mg/dL (transportation). A 20% negative bias was seen in samples retested after 1 h at RT.


CONCLUSIONS
Cold handling (prechilled tubes, iced transportation, 4°C centrifugation) was equivalent to RT for immediate measurement. An additional 1 h delay at RT led to a 20% decrease in uric acid. The cold handling measures required by the manufacturer are not necessary for uric acid testing of patients receiving rasburicase treatment, if testing is performed without delay.
Department of Pathology, Center for Advanced Molecular Diagnostics, Brigham and Women’s Hospital, Boston, MA 02115, USA. nlindeman@partners.org
Neal I
NI
Lindeman
Stacy E F
SE
Melanson
Anne
A
McDonnell
Daniel J
DJ
DeAngelo
Petr
P
Jarolim
D001774:Blood Chemical Analysis; D006801:Humans; D012034:Refrigeration; D013048:Specimen Handling; D015275:Tumor Lysis Syndrome / Q000097:blood / Q000188:drug therapy*; D014503:Urate Oxidase / Q000097:blood / Q000378:metabolism / Q000627:therapeutic use*; D014527:Uric Acid / Q000097:blood*
C469709:rasburicase; D014527:Uric Acid; D014503:Urate Oxidase