Background: BK virus (BKV) infection in renal transplant 
patients is a constant concern. As BK-induced nephritis may 
lead to graft failure, detection of the virus is of significant 
clinical importance. While the diagnosis of BKV infection 
can be made on H&E stained slides, immunohistochemistry 
allows for greater detection. The goal of this study was to 
compare the effectiveness of PCR to conventional 
(Hematoxylin and Eosin [H&E]) and immunohistochemistry 
for BKV.  
Design: Sixty-five renal biopsies from renal transplant 
patients were selected; 26 had definitive histologic and/or 
immunohistochemistry evidence of BKV and the remaining 
39 cases lacked sufficient evidence. DNA extraction was 
performed and PCR was conducted. In addition, analysis was 
performed on 49 renal biopsies taken from nontransplanted 
patients to establish specificity. 
Results: In the 26 cases with BKV infection by 
H&E/immunohistochemistry, PCR detected BKV in 10 
cases (62% sensitivity). In the control group, no evidence of 
BKV was shown by PCR (100% specificity). Of the 39 cases 
with suspicion of
 BKV 
but
 negative 
H&E/immunohistochemistry, PCR found 2 cases with BKV. 
No viral inclusions were seen on H&E, but 
immunohistochemistry had not been performed. Subsequent 
immunohistochemistry showed focal BK positivity and   confirmed PCR detection.  
Conclusions: These findings indicate that PCR is a highly 
specific detection method of BKV, although the sensitivity 
is 
low when compared to traditional H&E and 
immunohistochemistry methods. In light of these findings, 
the use of PCR may be particularly useful in cases with 
equivocal findings on H&E or immunohistochemistry.