Poster Board II-217
Molecular monitoring of the CMV viral load in the blood after allogeneic hematopoietic cell transplantation (allo-HCT) by quantitative real-time polymerase chain reaction (RQ-PCR) assays is considered as the most important measure for CMV disease prevention and may prompt the initiation of preemptive therapy. Molecular assays have a high negative predictive value, yet their precise role in the establishment of CMV infection in biological specimens other than plasma has not been defined conclusively. Furthermore, several technical aspects remain unresolved, in particular the use of cut-offs for positivity, given that, generally, viral loads (viral genome copies, VGC) less than 0,5-2,5log10 cannot provide linearity in the results. We retrospectively evaluated the clinical significance of positive RQ-PCR tests for CMV DNA in biological fluids other than plasma from 73 patients after allo-HCT, with a special emphasis on samples with a low viral load (<500 VGC/ml). All patients had undergone allo-HCT for hematologic malignancies after myeloablative (62/73) or reduced intensity conditioning regimen (11/73). The prevention strategy for herpesviruses reactivation included anti-viral chemoprophylaxis with acyclovir/valacyclovir, IVIG prophylaxis and the administration of leukodepleted blood products. The viral load in plasma and urine was monitored once weekly by RQ-PCR. Other bodily fluid samples were tested only in symptomatic patients. We evaluated 92 CMV positive samples documented in urine (n=67), gastric fluid (GF) (n=13) and bronchoalveolar lavage (BAL), (n=12). RQ-PCR examination of paired plasma samples revealed concordant CMV viremia in only 23/92 cases (25% in urine, 31% in GF, 17% in BAL). Overall, forty-six of 92 (50%) samples were obtained from cases with clinically symptomatic disease: (i) cystitis, n=23/67 (34%) cases; (ii) gastritis, n=13/13 (100%) cases; (iii) pneumonia, n=10/12 (83%) cases, of which, however, only two were attributed solely to CMV (the remainder were considered of mixed etiology, either concomitant bacterial/fungal infection or GVHD-related). All cases with symptomatic disease received appropriate treatment with valgancyclovir/gancyclovir or foscarnet for a minimum of 15 days. To further refine the interpretation of RQ-PCR results and ensure linearity, a cut-off of 500 CMV VGC/ml was applied. With this cut-off, samples were assigned to a low- or high-positive group (A or B, respectively). Group A included 41/67 urine samples (61%), 7/13 GF samples (54%) and 5/12 BAL samples (42%). Among cases with a low-positive urine sample assigned to group A, resolution of the infection (negative RQ-PCR in at least two subsequent samples) without treatment was noted in only 14/41 cases (34%). The remainder (27/41, 66%) had persistent CMV positivity and eventually developed CMV cystitis, as did all group B cases. Concomitant CMV viremia was detected in 4/41 (9.7%) group A and 10/27 (37%) group B cases with a positive urine sample. We conclude that the molecular determination of CMV viral load in biological fluids other than blood by RQ-PCR offers diagnostic information of clinical relevance for the detection and prevention of CMV cystitis and, also, CMV gastritis after allo-HCT. A low molecular viral load in urine should alert the clinician to the possibility of impending CMV disease. Larger prospective studies are strongly warranted in order to define universally accepted thresholds that would assist in clinical decision-making and thus minimize the toxicity of unnecessary treatment. The clinical utility of this approach in BAL samples remains questionable.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.