Analytical and clinical performance characteristics of the Simplexa BK virus quantitative PCR assay for the diagnosis of polyomavirus-associated nephropathy in renal transplant recipients using plasma and urine specimens.

BACKGROUND

Polyomavirus-associated nephropathy is a significant cause of kidney rejection in renal transplant recipients. Quantification of BK viral load in plasma and urine can predict the development of polyomavirus-associated nephropathy, though each assay requires careful evaluation of analytical and clinical performance characteristics for optimal use.

OBJECTIVES

This study evaluated the analytical and clinical performance characteristics of the Simplexa BK virus quantitative PCR assay.

STUDY DESIGN

Analytical validation was performed using commercial standards, BK virus stock culture, and patient specimens. Clinical performance was evaluated using biopsy-proven BK nephropathy as the gold standard.

RESULTS

The Simplexa BK virus quantitative PCR assay was linear over a range of 2.7-10.4 log(10) copies/mL. Limit of detection was 2.7-2.8 log(10) copies/mL in plasma and urine samples. Sensitivities were 100% and 100% and specificities were 84% and 86% for plasma and urine samples, respectively, when compared to a reference BK assay. Clinical cutoff values of 4.0 log(10) copies/mL (plasma) and 7.5 log(10) copies/mL (urine) yielded 100% sensitivity and specificities of 87.5% and 85%, respectively, for biopsy-proven polyomavirus nephropathy.

CONCLUSIONS

The Simplexa BK virus quantitative PCR assay has high sensitivity and acceptable analytical characteristics for clinical use. The clinical cutoff values presented here provide a rational approach to the monitoring and treatment of renal transplant recipients for polyomavirus-associated nephropathy.