Pre-emptive antiviral therapy for active CMV infection in adult allo-SCT patients guided by plasma CMV DNAemia quantitation using a real-time PCR assay: clinical experience at a single center

Pre-emptive antiviral therapy is the first-choice strategy for the prevention of CMV end-organ disease in the allo-SCT setting.1 In recent years, most institutions, including ours, have switched from the pp65 antigenemia assay (AG) to quantitative real-time PCR methods (QRT–PCR) for the guidance of pre-emptive antiviral therapy. Nevertheless, there are scarce published data as to how both strategies compare in terms of their clinical efficacy.2, 3, 4, 5 Although the criteria for initiation and cessation of pre-emptive antiviral therapy guided by the AG assay are rather standard across transplantation centers, there are no consensus criteria as to how active CMV infection should be managed in the QRT–PCR era.1 In fact, no validated CMV DNA load threshold (in either whole blood or plasma) exists for the inception of antiviral therapy, nor has a consensus been reached as to when antiviral treatment should be stopped (first negative QRT–PCR result/second negative QRT–PCR result/decrease of CMV DNA load below the cutoff for initiation of pre-emptive antiviral therapy). We retrospectively reviewed clinical and virological data from 147 consecutive patients who underwent T cell-replete allo-SCT at our center between January 2006 and May 2012. Until April 2010 (group I; n=90), CMV surveillance was performed in parallel by the AG assay and by a plasma real-time PCR assay (Abbott CMV PCR Kit, Abbott Diagnostics, Des Plaines, IL, USA).6 In this group, pre-emptive therapy was initiated upon a positive AG assay (1 positive cell/200 000 polymorphonuclear leukocytes) and stopped upon two consecutive negative results after a minimum of 2 weeks of treatment, as previously described.6 Since May 2010 (group II; n=57), virological monitoring was exclusively performed by QRT–PCR, and pre-emptive therapy was initiated upon a plasma CMV DNAemia threshold level of 500 CMV DNA copies/mL and was discontinued after two consecutive PCR-negative (undetectable) results, after a minimum of 2 weeks of treatment. Virological monitoring was performed twice a week in the presence of active CMV infection and once a week otherwise (until day 120 after allo-SCT, and at each patient visit afterwards). Only episodes occurring during the 1st year after allo-ST were taken into consideration for the analyses described herein. Diagnosis and treatment of CMV end-organ disease was done following consensus criteria.7 Active CMV infection was defined by a positive QRT–PCR or AG test (in episodes with negative PCR results). A recurrent episode of active CMV infection was that occurring at least 15 days after clearance (first negative PCR result) of the preceding episode. Type A episodes were those in which plasma CMV DNA load decreased upon inception of antiviral therapy, until clearance. Type B episodes were those in which rising levels of CMV DNAemia (increases five-fold) were demonstrated after the implementation of antiviral therapy.8

As shown in Table 1, the demographic and clinical characteristics of patients in both groups were not significantly different. As shown in Table 2, the incidence rate of episodes of active CMV infection and that of recurrent episodes occurred more frequently in patients in group I than in those in group II, though statistical significance was not reached. This was most likely due to the different length of the follow-up period for patients in both groups.

Table 1 Demographic and clinical data of patients guided with the pp65 antigenemia assay or with a real-time PCR assay
Table 2 Incidence of features of active CMV infection in patients guided with the pp65 antigenemia assay (AG) or with a real-time PCR assay (QRT–PCR)

The proportion of patients receiving pre-emptive antiviral therapy for first or recurrent episodes of active CMV infection did not vary significantly between groups (Table 2). This is in contrast to previous data obtained in two randomized controlled clinical trials targeting children and young adults,2 or adult patients receiving unrelated allografts.4 Our data are in line, however, with those recently published by Green et al.,5 using a CMV DNA load-based risk-adapted pre-emptive antiviral strategy. Our finding was not unexpected, as we have previously shown that an AG level of 1 positive cell/200 000 PMNLs corresponded roughly to 250 CMV DNA copies/mL.6 The above discrepancies are likely to be related to the different study design, as well as to differences in the clinical characteristics of patients, the sensitivity of the QRT–PCR employed for CMV surveillance and the CMV DNA load threshold established for initiation of antiviral therapy.

The duration of antiviral treatment of first episodes of active CMV infection was significantly longer in patients in group II than in patients in group I. A trend towards a longer duration of antiviral treatment was also observed for the first relapsing episodes. The above differences were not related to the antiviral therapy regimen implemented (not shown). These can be explained by the fact that clearance of CMV DNAemia proceeds at a slower rate than that of AG,6 and that a rather conservative criterium was employed for the cessation of pre-emptive antiviral therapy (two consecutive negative QRT–PCR results) in our cohort.

The kinetics of CMV DNAemia clearance following the initiation of antiviral therapy in the initial and first relapsing episodes of active CMV infection were comparable in both groups (Table 2). The incidence of CMV end-organ disease in both the time periods was not significantly different.

The major limitation of the current study is its observational retrospective nature. A randomized controlled clinical trial is undoubtedly the most adequate clinical design to address this issue. In summary, our data indicate that a plasma CMV DNA load of 500 copies/mL (1500 IU/mL,9) appears a safe and convenient threshold level for the initiation of pre-emptive therapy, irrespective of the patient’s risk of CMV end-organ disease. Nevertheless, cessation of antiviral therapy upon the second consecutive QRT–PCR negative result leads to an increase in the duration of antiviral treatments.

Studies such as ours and those of Green et al.5 highlight the need for centers using QRT–PCR assays for the guidance of pre-emptive antiviral therapy of active CMV infection to report on their clinical experience in order to standardize the criteria for the initiation and cessation of antiviral therapy. Comparison of the data obtained across transplant centers is now possible with the advent of the 1st WHO International Standard for CMV for Nucleic Acid Amplification (NAT)-based assays,10 which allows normalization of CMV DNA loads measured using different extraction methods and QRT–PCR assays.


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We thank Julia García and Mónica Reig for their technical assistance. This research was supported by a grant (09/1117) from FIS (Fondo de Investigaciones Sanitarias, Ministerio de Sanidad y Consumo, Spain). PA is a research fellow of the Asociación Española contra el Cáncer (AECC).

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Correspondence to D Navarro.

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Solano, C., Muñoz-Cobo, B., Giménez, E. et al. Pre-emptive antiviral therapy for active CMV infection in adult allo-SCT patients guided by plasma CMV DNAemia quantitation using a real-time PCR assay: clinical experience at a single center. Bone Marrow Transplant 48, 1010–1012 (2013).

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