Background: Low level CMV viremia is common, and may either progress to higher viral loads that require therapy, or may spontaneously resolve. The clinical predictors of progression and spontaneous viral clearance are not well defined.

Methods: We performed a retrospective cohort study of solid organ transplant recipients who had onset of low-level CMV viremia (< 1000 IU/mL) from January 2010-December 2014. Progression was defined as a rise in viral load ≥ 1000 IU/ml or development of symptoms. Spontaneous clearance was defined as a decline in viral load below the assay threshold without antiviral treatment. Clinical and laboratory parameters were assessed for their predictive value. Patients were followed for 8 weeks from the onset of viremia. CMV viremia doubling time was calculated for a subset of patients with sufficient viral load timepoints.

Results: A total of 123 patients were identified as follows: lung (n=56), liver (n=52), kidney (n=7), Other (n=8); median age was 60 years (range 28-79). Median CMV viral load at onset was 318 IU/ml. Of these, 61/123 (49.6%) patients progressed to a high viral load, 28/123 (22.8%) cleared viremia spontaneously, and 34/123 (27.6%) had persistent low level viremia at the end of followup. A subset of patients also developed CMV disease (syndrome or tissue-invasive disease) at low level viremia (11/123; 8.9%). In multivariate analysis, CMV mismatch, transplant type, lymphopenia, use of anti-lymphocyte globulin, and prednisone (use or dose) were not significantly associated with progression to high viral load. However, prior treated CMV infection anytime post-transplant was protective against progression (p=0.039; OR 9.89 (95%CI 1.13, 86.78)). In a subset of 12 patients with progression, the doubling time for CMV viremia was a median of 11 days (range 4-34).

Conclusion: Our study finds that previous CMV infection significantly decreased the likelihood of low level viremia progression suggesting that CMV immunity plays a role in progression. No other clinical predictors for progression or clearance were noted. Therefore, a first episode of low-level CMV viremia warrants close follow-up and possibly earlier initiation of treatment.

CITATION INFORMATION: Alghamdi A, Humar A, Natori Y, Husain S, Singer L, Renner E, Rotstein C, Kumar D. Clinical Predictors of Progression and Clearance of Low Level CMV Viremia in Solid Organ Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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