Comparison of quantitative PCR values and antigenemia for CMV monitoring in hematopoietic cell transplant recipients.

Cytomegalovirus (CMV) reactivation remains a major complication after hematopoietic cell transplantation (HCT), particularly in high-risk settings. Although the antigenemia (AG) assay has long been the standard CMV monitoring tool in Japan, quantitative PCR (qPCR) offers improved sensitivity and is now widely adopted. We analyzed a total of 1878 samples from 231 HCT recipients who underwent CMV monitoring at multiple centers. We evaluated the correlation between AG and qPCR results, determined qPCR thresholds equivalent to AG positivity, and compared actual AG-guided therapy durations with simulated qPCR-guided therapy. Among 1878 sample sets, AG and qPCR showed strong correlation (r = 0.65) and high concordance (87.6%). Median qPCR values increased with AG positivity level. ROC analysis identified qPCR cut-offs corresponding to 2 and 10 AG-positive cells as 99.5 and 815 IU/mL, respectively. Of 57 qPCR-only episodes, 32 resolved without AG conversion; higher qPCR levels were associated with treatment need. Simulated qPCR-guided therapy durations closely matched AG-guided therapy (median 4 weeks), but some cases required longer treatment. qPCR-based CMV monitoring is concordant with AG and feasible for preemptive therapy. Careful interpretation of low-level viremia is warranted to avoid overtreatment. Further data are needed to refine qPCR thresholds in transplant settings.