Costa Cristina, Bergallo Massimiliano, Astegiano Sara, Terlizzi Maria Elena, Sidoti Francesca, Segoloni Giuseppe P, Cavallo Rossana
Dipartimento di Sanità Pubblica e Microbiologia, Laboratorio di Virologia, Università di Torino, Italy.
Nephrol Dial Transplant. 2008 Oct;23(10):3333-6. doi: 10.1093/ndt/gfn289. Epub 2008 May 25.
BK virus-associated nephropathy (BKVAN) is one of the most common viral diseases affecting renal allografts. Screening for viral replication may allow for earlier intervention with reduced allograft loss. A plasma viral load >10(4) copies/mL of BKV DNA is recommended for a presumed diagnosis of BKVAN.
We monitored BKV load on serum and urine samples by Real-Time TaqMan PCR in 229 renal transplant recipients in the first year post-transplantation. Overall, 2025 serum and 2025 urine samples were evaluated. A graft biopsy was performed in 47/229 patients to investigate the declining renal function. Operating characteristics [sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV)] and receiver operating characteristic (ROC) curve analysis at different viral load values were calculated.
Serum BKV viral load was >10(4) in 5/229 patients (2.2%). A histological diagnosis of BKVAN was made in 3/229 patients (1.3%): 3/5 (60.0%) among those with serum viral load >10(4) and 3/4 (75.0%) in those with >1.6 x 10(4). Operating characteristics of a serum BK load of 10(4) for the diagnosis of BKVAN were as follows: sensitivity, 100%; specificity, 99.1%; NPV, 100%; PPV, 59.4%. Specificity and PPV rose to 99.6% and 75.0% when using a cut-off level of 1.6 x 10(4) copies/mL.
The recommended level of BK viraemia of 10(4) copies/mL is useful to identify patients at risk of BKVAN, although specificity and PPV increase by using a cut-off level of 1.6 x 10(4) copies/mL. BK replication may occur in the first 3 months post-transplantation and subsequently recede. Therefore, the temporal profile of BKV replication has to be accurately evaluated and occasionally elevated values should prompt a closer monitoring.
BK病毒相关性肾病（BKVAN）是影响肾移植受者的最常见病毒性疾病之一。筛查病毒复制情况可能有助于更早进行干预，减少移植肾丢失。对于疑似BKVAN的诊断，推荐血浆中BK病毒DNA载量>10⁴拷贝/mL。
我们通过实时TaqMan PCR监测了229例肾移植受者移植后第一年血清和尿液样本中的BK病毒载量。总共评估了2025份血清样本和2025份尿液样本。对47/229例患者进行了移植肾活检，以研究肾功能下降情况。计算了不同病毒载量值时的操作特征[敏感性、特异性、阴性预测值（NPV）、阳性预测值（PPV）]以及受试者工作特征（ROC）曲线分析。
229例患者中有5例（2.2%）血清BK病毒载量>10⁴。229例患者中有3例（1.3%）经组织学诊断为BKVAN：血清病毒载量>10⁴的患者中3/5（60.0%），病毒载量>1.6×10⁴的患者中3/4（75.0%）。血清BK载量为10⁴用于诊断BKVAN的操作特征如下：敏感性为100%；特异性为99.1%；NPV为100%；PPV为59.4%。当使用1.6×10⁴拷贝/mL的临界值时，特异性和PPV分别升至99.6%和75.0%。
推荐的BK病毒血症水平10⁴拷贝/mL有助于识别有BKVAN风险的患者，尽管使用1.6×10⁴拷贝/mL的临界值时特异性和PPV会增加。BK病毒复制可能在移植后前3个月发生，随后消退。因此，必须准确评估BK病毒复制的时间特征，偶尔出现的升高值应促使进行更密切的监测。
