Korean J Lab Med.  2004 Feb;24(1):22-26.

A Method for Measuring Uric Acid Accurately in Refrigerated Urine Specimens

• Kim HS
• Park IK
• Kim SE
• Sir JU
• Kim TY

Abstract

BACKGROUND
There have been many reports about the decrease in uric acid concentration in refrigerated urine specimens as compared to fresh urine. In an effort to correct this problem, pre-treatment steps such as the pre-alkalinization of sample tubes or the pre-dilution of urine were recommended before the refrigeration. The authors sought to find a way to correct the decreased measurement of uric acid concentrations in the refrigerated urine samples. METHODS: The uric acid concentrations of 53 fresh urine samples were measured and all were refrigerated. After 24 hours of refrigeration, the samples were measured for their uric acid concentrations (the refrigerated samples). All samples were then mixed well with 1 M NaOH 20 microL/mL (the refrigerated-alkalinized samples) and they were again measured for their uric acid concentrations. The differences of uric acid concentrations between the fresh urine samples and the refrigerated samples and also between the fresh urine samples and the refrigerated-alkalinized samples were noted. RESULTS: In a precipitated group of 14 urine samples, the compared results between the fresh urine and the refrigerated urine showed a statistically significant difference (P<0.05). However, there were no significant differences between the fresh urine and the refrigerated-alkalinized urine (P=0.49). In a non-precipitated group, there were no significant differences between the fresh urine and the refrigerated urine, or between the fresh urine and the refrigerated-alkalinized urine (P=0.47, P=0.18). CONCLUSIONS: For 24 hour refrigerated urine samples, the addition of 1 M NaOH 20 microL/mL to the urine samples after refrigeration was recommended for accurate measurement of uric acid concentration.

Keyword

24 hour Urine; Precipitation; Uric acid; NaOH

MeSH Terms

Refrigeration
Uric Acid*
Uric Acid