Table 1.

Risk Factors for Cytomegalovirus Resistance in Hematopoietic Cell Transplant Recipients^a,b

Risk Factor
Host factors
Prolonged antiviral CMV drug exposure (>3 mo)
Previous antiviral CMV drug exposure
Recurrent CMV infection
Inadequate antiviral CMV drug absorption and bioavailability
Inadequate antiviral CMV oral prodrug conversion
Variation in antiviral CMV drug clearance
Subtherapeutic antiviral CMV drug level
Poor patient compliance with antiviral drug regimen
T-cell depletion
Haploidentical, allogeneic, or cord blood HCT
Delayed immune reconstitution
CMV-seropositive recipient and CMV-seronegative donor
Treatment with antithymocyte antibodies
Active GVHD
Young age
Congenital immunodeficiency syndromes
Viral factors
CMV viral load rise while receiving treatment (after >2 wk of adequate dosing)
Failure of CMV viral load to fall despite appropriate treatment
Rise in CMV viral load after initial decline while receiving appropriate treatment
Intermittent low-level CMV viremia
High CMV viral loads

Abbreviations: CMV, cytomegalovirus; GVHD, graft-vs-host disease; HCT, hematopoietic cell transplantation.

^aModified with permission from El Chaer et al 1.

^bMost of the risk factors for CMV resistance pertain to solid organ transplant recipients as well, in addition to graft rejection (instead of GVHD) and CMV-seropositive donor and CMV-seronegative recipient.