尿液与血液病毒载量在肾移植受者BK病毒性肾病诊断中的应用

The cut-off value of BK virus DNA load in urine or plasma for diagnosis of BKVN in renal transplantation recipients

目的对比尿液和血液样本BK病毒DNA载量检测在肾移植受者BK病毒性肾病诊断中的应用价值。方法2011年2月至2012年1月间接受同种异体肾移植的受者88例，应用实时荧光定量聚合酶链反应法对其血液和尿液样本定期进行BK病毒DNA载量检测；对具备指征的移植受者行移植肾组织活检，通过免疫组织化学法明确BK病毒性肾病（BKVN）诊断。结果88例中病毒尿症者35例（39．8％），病毒血症者18例（20．5％），病理学明确诊断为BKVN者5例（5．7％）。统计学分析显示，BKVN患者尿液和血液样本中的BK病毒DNA载量均显著高于非BKVN患者（P〈0．05）。尿液样本预测BKVN发生的敏感性为100％，特异性为57．7％（P=0．003）；血液样本预测BKVN发生的敏感性为100％，特异性为82．9％（P=0．0002）。将尿液BK病毒DNA〉~10^5拷贝／ml和血液病毒DNA≥10^5拷贝／ml做为预测诊断BKVN发生的阳性指标时，尿液阳性指标的阳性预测值为26．3％，阴性预测值为95．7％；血液阳性指标的阳性预测值为83．3％，阴性预测值为98．8％。结论血液BK病毒DNA载量≥10^5拷贝／ml，可作为辅助诊断BKVN发生的阳性指标，而尿液BKVDNA载量监测可作为BKV感染的筛查。

Objective To compare the applied value of BK virus DNA load detection in urine and plasma for diagnosis BK virus nephropathy （BKVN） in renal transplantation recipients. Method In 88 renal transplantation recipients receiving renal allograft from February 2011 to January 2012 in our institute, BK virus DNA load in urine and plasma was detected by using real-time PCR, and renal biopsy was performed on the recipients with gradual deterioration of the graft function or the loads of t3KV replication being very high. The diagnosis of BKVN was confirmed by using immunohistochemistry. Results Of 88 recipients, there were 35 cases （39. 8%） of viruria, 18 cases （20. 5%） of viremia and 5 cases （5. 7%） of BKVN. The median BKV DNA load in both urine and plasma in BKVN recipients was significantly higher than in non-BKVN recipients （P^0. 05 ）. The viruria sensitivity and specificity for BKVN were 100% and 57. 3~ （P = 0. 03）, and the viremia sensitivity and specificity for BKVN was 100% and 82. 9% （P = 0. 0002）, respectively. We regraded viral load _-〉 105 copies/mL in plasma or 〉/107 copies/mL in urine as the best discriminant cut-off value to predict the disease and to identify patients at risk of developing BKVAN. The positive cut-off value of urine＇s positive predictive value （PPV＋） was 26. 3% and negative predictive vaule （PPV-） was 95.7%, and the positive cut-off value of plasma＇s positive predictive value （PPV＋） was 83. 3% and negative predictive vaule （PPV-） was 98. 8%. Conclusion The viral load 〉/105 copies/mL in plasma can be used as the best discriminant cut-off value to predict the disease and to identify patients at risk of developing BKVAN, but the cut-off value of urine should be only used for screening BKV infection.