Cytomegalovirus DNA in Transplant Recipients: Comparison of Whole Blood and Plasma Viral Loads

Background:  Cytomegalovirus (CMV) infection is a major cause of morbidity after solid organ (SOT) or stem cell transplantation (SCT). Currently, quantitative CMV DNA testing (QNAT) is the primary method for diagnosis and guiding treatment. There continues to be a debate on whether whole blood (WB) or plasma is the ideal sample for QNAT. Previous studies using laboratory-developed assays showed higher sensitivity with WB. However, the validity of this finding remains unknown in this era of highly sensitive QNAT calibrated to the WHO International standard.

Methods:  We conducted a single-center prospective study of SOT and SCT recipients with CMV disease to collect weekly paired plasma and WB samples. All samples were tested with the COBAS® AmpliPrep/COBAS® TaqMan® CMV Test (Roche Molecular Systems, Inc., Branchburg, NJ) with modification of the assay for testing WB.

Results:  A total of 88 patients were enrolled: 58 (61%) male subject; median age of 56.7 (range, 47.8 - 63.0) years; 46 (52%) SOT and 42 (48%) SCT recipients. Of the SOT recipients, 24 (52%) had asymptomatic viremia and 22 (48%) with disease. In the SCT group, 33 (79%) had asymptomatic viremia, and 9 (21%) with disease. Overall, there was modest agreement in qualitative results between plasma and WB viral load (VL) based on a total of 403 paired samples (total agreement=69.2%; kappa=0.49 [95% CI; 0.43, 0.56]). Among pairs in which the VL was quantifiable, correlation between plasma and WB VL was modest (r=0.699), with VL from WB higher than those from plasma by a consistent margin (Figure). Initial and peak VL (expressed as median with first and third quartile values) in both plasma and WB were significantly different between asymptomatic and symptomatic disease (Table).  

Conclusion:  The correlation between plasma and WB was modest, with higher VL observed in WB. Regardless of specimen type, higher VL was associated with symptomatic CMV disease.

 

CMV VL	N	Symptomatic (n=31)	Asymptomatic (n=57)	P valuea
Initial VL, plasma	83	4,880 (1,570, 20,800)	470 (290, 1,140)	<0.001
Peak VL, plasma	88	5,450 (1,570, 20,800)	825 (363, 2,030)	<0.001
Initial VL, whole blood	83	14,846 (1,988, 85,378)	5,004 (1,045, 8,247)	0.005
Peak VL, whole blood	88	27,641 (2,897, 100,091)	5,349 (1,631, 11,613)	0.002
a Kruskal-Wallis rank sum test