Analytical performance and clinical utility of a nucleic acid sequence-based amplification assay for detection of cytomegalovirus infection

A nucleic acid sequence-based amplification (NASBA) assay for qualitative d etection of human cytomegalovirus (CMV) pp67 mRNA was evaluated in a multic enter study, Negative results were obtained for all specimens from 50 CMV-s eronegative and 50 CMV-seropositive low-risk whole-blood donors, No interfe rence with CMV mRNA amplification was observed in the testing of 288 specim ens containing various potential interfering substances, nonspecifically re acting substances (including mRNA from other herpesviruses), and three anti coagulants, A total of 95% (50 of 51) of CMV-positive (cell culture- and an tigenemia immunofluorescence [AG-IFA]-positive) clinical specimens were pos itive by the NASBA assay. Results from different operators over multiple te sting days were consistent for each of four panel members containing differ ent concentrations of CMV mRNA indicating the reproducibility of the assay. The estimated 95% reliable upper detection limit of the assay was 600 mRNA copies; the lower limit of detection was less than 25 mRNA copies. The cli nical utility of the assay was evaluated with longitudinally collected spec imens from solid-organ transplant patients (n = 21), A total of 98% (81 of 83) of the specimens from CMV-negative patients were negative by the NASBA assay, while 90% (10 of 11) of patient specimens that were positive by cell culture or AG-IFA were positive by the NASBA assay. Positive NASBA assay r esults were obtained earlier than AG-IFA or cell culture results for 55% of the patients and at the same time for the remainder of the patients (45%), The overall agreement between the NASBA assay and current reference tests was 86% when active CMV infection was present, These studies indicate that the CMV pp67 mRNA NASBA assay has reproducible and sensitive performance ch aracteristics that should enable more rapid diagnosis of CMV infection.