[Clinical study of low cytomegalovirus viral load thresholds for preemptive antiviral therapy in hematopoietic cell transplant recipients].

To investigate the threshold of cytomegalovirus (CMV) DNAemia for preemptive antiviral therapy in patients with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Viral load between 1×10(3) copies/ml and 5×10(3) copies/ml was defined as low viral load by real time Q-PCR. Clinical data and outcome were collected. A total of 95 allo-HSCT recipients with low viral load from September 2014 to February 2015 were recruited in this study. The control group included 37 patients who received preemptive initial antiviral therapy. The other 58 patients didn't received antiviral treatment after positive viremia was confirmed. During monitoring, CMV viremia was cleared spontaneously in 17 patients of study group. Among 41 patients with continuous positive viremia in study group, 26 patients received antiviral therapy after second positivity including 18 with viral load >5×10(3) copies/ml, 2 with fever but still low viral load, 2 with hemorrhagic cystitis and low viral load, 4 with continuous low viral load. Eleven patients received antiviral therapy after the third positivity including 5 with viral load >5×10(3) copies/ml, 1 low viral load patient with fever and diarrhea, 5 with continuous low viral load. Only 4 patients received antiviral therapy after the fourth positivity of >5×10(3) copies/ml. In the study group, 35 cases received ganciclovir and 6 cases received foscarnet. The incidence of neutropenia did not differ significantly between study and control groups [minimum of neutrophil count: (1.63±0.41)×10(9)/L vs. (1.58±0.36)×10(9)/L]. The proportion of viral load greater than 5×10(3) copies/ml in the first week was comparable in two groups. Successful viral clearance rate was not statistically different (=0.87). Of all 95 patients, no CMV diseases developed, neither did patient die of CMV infection. Spontaneous clearance of viremia occurs in some patients receiving allo-HSCT with low CMV viral load. Delayed antiviral treatment of continuous positive viremia does not prolong the whole treatment duration, neither contributes to the progression of CMV diseases.