Comparing cytomegalovirus diagnostics by cell culture and quantitative nucleic acid testing in broncho-alveolar lavage fluids.

Leuzinger, Karoline; Stolz, Daiana; Gosert, Rainer; Nägele, Klaudia; Prince, Spasenija Savic; Tamm, Michael; Hirsch, Hans H

Many clinical laboratories have replaced virus isolation-in-cell-culture (VIC) for cytomegalovirus (CMV) by quantitative-nucleic-acid-testing (QNAT), rendering clinically relevant CMV-replication difficult to distinguish from CMV-shedding or latent infection. We compared direct VIC in 1109 consecutive bronchoalveolar lavage fluids (BALF) and a well-validated CMV-QNAT (Basel-CMV-UL111a-77bp). In the retrospective group-1 (N=694) and group-2 (N=303), CMV-QNAT was performed within 48 hours from 2-fold and 10-fold concentrated total nucleic acid (TNA)-eluates, respectively. In group-3 (N=112), 2-fold and 10-fold concentrated TNA-eluates were prospectively analyzed in parallel to VIC. CMV was detected by VIC in 79/694 (11%) and 26/303 (9%) of group-1 and -2, but in 114/694 (16%) and 57/303 (17%) by CMV-QNAT, respectively. Median CMV-loads were significantly higher in VIC-positive than in VIC-negative BALF. The likelihood for CMV-detection by VIC was 85% for BALF CMV-loads >4 log10 copies/mL. In the prospective group-3, CMV was detected by VIC in 10/112 (9%), and in 14/112 (13%) and 20/112 (18%) by CMV-QNAT, when using 2-fold and 10-fold concentrated TNA-eluates, respectively. Notably, CMV was undetectable by CMV-QNAT in 10 VIC-positive cases of group-1 and -2, but in none of group-3. We conclude that CMV-QNAT can be adopted to BALF diagnostics but require several careful steps in validation. CMV-QNAT loads >10'000 copies/mL in BALF may indicate significant CMV replication as defined by VIC, if short shipment and processing procedures can be guaranteed. Discordance of detecting CMV in time-matched plasma samples emphasies the role of local CMV replication, for which histopathology remains the gold standard of proven CMV pneumonia. This article is protected by copyright. All rights reserved.