Detection of Human Polyomaviruses in Urine from Bone Marrow Transplant Patients: Comparison of Electron Microscopy with PCR

Abstract

Background:We studied electron microscopy (EM) as an appropriate test system for the detection of polyomavirus in urine samples from bone marrow transplant patients. Methods: We evaluated direct EM, ultracentrifugation (UC) before EM, and solid-phase immuno-EM (SPIEM). The diagnostic accuracy of EM was studied by comparison with a real-time PCR assay on 531 clinical samples.Results: The detection rate of EM was increased by UC and SPIEM. On 531 clinical urine samples, the diagnostic sensitivity of EM was 47% (70 of 149) with a specificity of 100%. We observed a linear relationship between viral genome concentration and the proportion of urine samples positive by EM, with a 50% probability for a positive EM result for urine samples with a polyomavirus concentration of 10 6 genome-equivalents (GE)/mL; the probability of a positive EM result was 0% for urine samples with <10 3 GE/mL and 100% for urine samples containing 10 9 GE/mL. Conclusions: UC/EM is rapid and highly specific for polyomavirus in urine. Unlike real-time PCR, EM has low sensitivity and cannot quantify the viral load.

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“…The procedure is complicated and time-consuming, which obviously restricts the study. The SPIEM technique is considered to be the most sensitive and specific assay now available for virus detection [26]. Considering that the characteristics of exosomes are similar to those of a virus, we used SPIEM to study exosomes.…”

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