Multicenter evaluation of PCR methods for detecting CMV DNA in blood donors

BACKGROUND: CMV DNA screening may be a useful adjunct to serologic tests in distinguishing potentially infectious blood donations from those that are "CMV-safe." However, there is currently no consensus on the optimal assay m ethod for accurate detection of CMV DNA in donors. STUDY DESIGN AND METHODS: A blinded multicenter evaluation of seven CMV PCR assays was performed by five laboratories by using coded sets of analytica l controls and donor blood samples. RESULTS: Five assays displayed sufficient sensitivity for donor screening, as judged by consistent detection of a minimum of 25 CMV genome equivalents (geq) in analytical controls constructed to contain from 1 to 100 CMV geq in background DNA from 250,000 cells, while the other two assays displayed inadequate sensitivity. Three sensitive assays, two based on nested PCR dir ected at the UL93 and UL32 regions of the CMV genome and another test (Moni tor Assay, Roche), did not detect CMV DNA in samples from any of 20 pedigre ed CMV-seronegative, Western blot-negative (S-/WB-) donors. Two other assay s based on nested PCR occasionally detected CMV DNA in S-WB- samples, and o ne sensitive nested PCR assay directed at UL123 detected CMV DNA in a large proportion (85%) of S-WB- samples. CONCLUSION: Seven CMV PCR assays currently used for research and/or diagnos tic applications displayed marked variations in sensitivity, specificity, a nd reproducibility when applied to coded analytical and clinical control sa mples containing cellular DNA from the equivalent of 250,000 WBCs. These re sults will be useful in the selection of assays with performance characteri stics appropriate to donor screening objectives. They may also help explain discrepant findings from previous studies that used PCR to determine CMV D NA prevalence in seronegative and seropositive blood donors.