The use of unprocessed urine samples for detecting and monitoring BK viruses in renal transplant recipients by a quantitative real-time PCR assay

Abstract

Results of quantitative BK viral load using real-time quantitative PCR (rt-QPCR) were compared using two types of samples, extracted urine DNA and unprocessed urine. An excellent correlation was observed in quantitative viral load between unprocessed urine and extracted urine DNA samples. ( R 2 = 0.96, p < 0.001). Compared to extracted urine DNA when a small sample volume of unprocessed urine was used (2 μl per PCR reaction), 100% concordance is detection of BKV DNA was observed in 124 samples (106 positive and 18 negative) collected from renal transplant recipient (RTR). There was no significant difference in the quantitative BK viral load (log 10 copies/ml) detected in extracted urine DNA (median = 7.82) compared to unprocessed urine (median = 7.17). Urine pH in the range of 5.2–7.1 and specimen freezing had no effect on the rt-QPCR reaction. The partial inhibition of the rt-QPCR reaction observed when 5 μl sample volume of unprocessed urine was used was markedly reduced at a sample volume of 2 μl. Using unprocessed urine for rt-QPCR detection of BK viral load is cost-saving while maintaining the sensitivity and accuracy associated with the use of extracted urine DNA, making a clinical BKV surveillance strategy in RTR based on urinary sample screening using rt-QPCR as the first line test more feasible.