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Nevertheless, the impact of such sequential test combination on the test performance characteristic has never been evaluated. Sequential screening with urine cytology followed by BKV serum quantitative PCR potentially reduces screening cost. Its negative predictive value (NPV) to rule out BKVAN is almost 100%. Urine cytology for decoy cell is a surrogate marker of BK viremia. However, a staged approach measuring BK viral load in urine followed by serum with PCR test was not cost-effective when compared with BKV serum PCR test alone. However, the high screening cost is the major obstacle for implementing universal serum BK viral load screening in post-kidney transplant recipients.ĭetection of BK viremia usually precedes the development of BK viremia or BKVAN. The current American Society of Transplantation guidelines have also supported screening BKV viremia with or without prior BKV viremia screening. Screening serum viral load alone with polymerase chain reaction (PCR) test has been shown to have satisfactory test performance and is the recommended screening tool according to the KDIGO guidelines. Hence, routine screening of BKV infection is now recommended to allow early detection of BKV replication and prompt reduction of immunosuppressant at earlier stages of the disease. BKVAN is mostly diagnosed late in the advanced stage of the disease when irreversible damage has already occurred, leading to graft loss in 40-60% of the affected individuals. An increasing prevalence has been noted in recent years, and this trend has been correlated with the use of newer and more potent immunosuppressive agents. Conclusions: Our study had demonstrated a favorable test performance and cost efficiency of 2-stage BKV screening.īK virus-associated nephropathy (BKVAN) occurs in 1-10% of renal transplant recipients.
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Two-stage screening also had superior positive predictive value and is cost effective when BKV-associated nephropathy prevalence is below 94%. Sequential 2-stage screening resulted in loss in sensitivity but a net gain in specificity (viral load threshold ≥10 4 copies/ml - sensitivity, 75% (95% CI 60-91) specificity, 98% (95% CI 95-99)). The sensitivity and specificity of urine cytology alone were 91% (95% CI 79-100) and 74% (95% CI 60-91), respectively. Results: At a viral load threshold of ≥10 4 copies/ml, the sensitivity and specificity of quantitative PCR alone were 83% (95% CI 69-96) and 91% (95% CI 83-97), respectively. A probabilistic model was constructed to evaluate the test performance and screening cost of 2-stage screening, and was compared with screening with urine cytology or serum viral load alone. Methods: Ninety-five kidney transplant recipients who had BKV serum quantitative PCR/urine cytology tested and verified with histopathology (the reference gold standard) were included. We aimed to evaluate the test performances and screening cost of sequential 2-stage screening consisting of urine cytology followed by BKV serum quantitative polymerase chain reaction (PCR). Background: Incorporating urinary cytology in BK virus (BKV) screening algorithm potentially reduces the screening cost for BK viral nephropathy.