Non-invasive urinary sediment double-immunostaining predicts BK polyomavirus associated-nephropathy in kidney transplant recipients

Abstract

Background: The positive predictive value (PPV) of urinary decoy cells for diagnosing BK polyomavirus associated-nephropathy (BKPyVAN) is low. This study was designed to increase the PPV of urinary decoy cells for diagnosing BKPyVAN in kidney transplant recipients.Methods: A total of 105 urine sediment samples from 105 patients with positive BK viruria and decoy cells were evaluated by automatic double-immunostaining with anti-HGD (a renal tubular marker) antibody + anti-SV40-T antibody or anti-S100P (an urothelial marker) antibody + anti-SV40-T antibody.Results: Of the 105 patients, 76 (72.4%) had both HGD(+)/SV40-T(+) cells and S100P(+)/SV40-T(+) cells (group A), 24 (22.9%) had only S100P(+)/SV40-T(+) cells (group B), and 5 (4.6%) had only S100P(−)/ HGD(−)/SV40-T(+) cells (group C). Seventy patients in group A (92.1%), 3 patients in group B (12.5%), and no patients in group C were diagnosed with BKPyVAN. The area under the ROC curve of predicting BKPyVAN by decoy cells was 0.531 (0.431-0.630), with an optimal cut-off value of 29 (per 10 high power field), a sensitivity of 45.8% (95% CI: 34.0-58.0%), and a specificity of 68.8% (95% CI: 50.0-83.9%).Besides, the area under the ROC curve of predicting BKPyVAN by plasma BKPyV load was 0.735 (95% CI: 0.632-0.822), with an optimal cut-off value of 1,000 copies/mL, a sensitivity of 61.1% (95% CI: 48.9-72.4%) and a specificity of 84.2% (95% CI: 60.4-96.6%). In contrast, the PPV, negative predictive value, sensitivity, and specificity of HGD(+)/SV40-T(+) cells for diagnosing BKPyVAN were 92.1% [95% confidence interval (CI): 83.0-96.7%], 89.7% (95% CI: 71.5-97.3%), 95.9% (95% CI: 87.7-98.9%), and 81.3% (95% CI: 63.0-92.1%) respectively.Conclusions: Double-immunostaining with anti-HGD or anti-S100P and anti-SV40-T antibodies helps to identify the origin of decoy cells and diagnose BKPyVAN.

Detection of Proximal Tubule Involvement by BK Polyomavirus in Kidney Transplant Recipients With Urinary Sediment Double-Immunostaining

“…Decoy cells were found in all 76 patients [median count 25.5/10 HPFs, interquartile range (IQR): 11.0-45.0]. Four classical morphological types of decoy cells had been described in our previous study (6). As shown in Figure 1, the classic decoy cell contained enlarged, basophilic, and homogeneous amorphous ground glass-like intra-nuclear inclusion bodies.…”

“…It is worth noting that some studies have suggested that BKPyV spreads in the urinary epithelium through a retrograde pathway, that is, in the order of collecting tube, distal tubule, proximal tubule, and finally glomerular parietal epithelium (5)(6)(7)(8). Other studies have found that early stage of BKPyVAN was focally distributed in the kidney and mainly in the medulla area (1,28,30,31).…”

“…The chromogen for all 3 markers was diaminobenzidine (DAB). The IHC protocol for CD10, HGD, and 58K has been reported elsewhere (6,(23)(24)(25).…”

“…During the progression of BKPyVAN, BK polyomavirus (BKPyV) usually infects the pelvis, collecting ducts, distal tubules, and subsequently proximal tubules (5)(6)(7)(8). In some cases of severe infection, BKPyV can spread to the glomerular parietal epithelial cells (9)(10)(11).…”

“…The main reason is that decoy cell can be derived from either renal tubular epithelium or ureteral and bladder transitional epithelium (16). Our previous study has proved that double-immunostaining with anti-homogentisate 1, 2-dioxygenase (anti-HGD) and anti-SV40-T on urinary sediment can effectively improve the PPV of decoy cell for diagnosing BKPyVAN (6). However, HGD is expressed in both proximal and distal tubular epithelium.…”