Urine specimens are valuable to investigate kidney disease and antiretroviral nephrotoxicity. We observed large rust-colored pellets in some urine specimens after overnight storage at 4oC. Testing of supernatant under varying conditions demonstrated that this phenomenon reflects supersaturation and precipitation of uric acid in samples with high uric acid concentration. Delays in processing, even with refrigeration, may decrease the sensitivity of urine uric acid testing, with implications for the evaluation of proximal tubulopathy related to tenofovir.
Mount Sinai School of Medicine, The Samuel F. Bronfman Department of Medicine, Division of Nephrology, New York, USA.
Correspondence to Christina M. Wyatt, Mount Sinai School of Medicine, The Samuel F. Bronfman Department of Medicine, Division of Nephrology, One Gustave Levy Place, New York, Box1243, NY 10029, USA. Tel: +1 212 241 6689; e-mail: firstname.lastname@example.org
Received 13 February, 2013
Revised 13 March, 2013
Accepted 14 March, 2013