*Purpose: Valganciclovir (VGCV) is FDA-approved for CMV prophylaxis in children aged one month to sixteen years old using the Pescovitz algorithm (7 x body surface area x creatinine clearance). There are reports of VGCV overdoses in children with low body weight, low body surface area, and overestimated creatinine clearance with this algorithm. Supratherapeutic VGCV dosing can increase risk of neutropenia. The purpose of this study was to compare the incidence of neutropenia and CMV infection or disease between the Pescovitz (PES) and weight-based (WB) dosing algorithms (15 to 20 mg/kg/day).

*Methods: A single-center, IRB-approved, retrospective chart review from 2010 to 2018 was performed on pediatric heart, liver, and kidney transplant recipients aged 1 month to 16 years, who received VGCV for CMV prophylaxis following transplantation. Patients were stratified into two dosing algorithms: PES and WB. Data were collected from the initiation of VGCV prophylaxis to 30 days after discontinuation of therapy. The primary objective was the incidence of neutropenia (ANC less than 1500/μL) in patients receiving VGCV dosed by the PES algorithm compared to WB dosing. Secondary objectives included the incidence of moderate neutropenia (ANC less than 1000/μL), severe neutropenia (ANC less than 500/μL), CMV viremia, CMV disease, other infections and number of patients who received granulocyte colony stimulating factors (G-CSF) to treat neutropenia.

*Results: This study included 187 transplant recipients who received VGCV dosed via the PES (62 recipients) or WB (125 recipients) dosing. The incidence of neutropenia was higher in the PES group (69.4%) compared to the WB group (53.6%) (p = 0.04). The incidence of moderate neutropenia occurred in 50% of the PES group and 31.2% of the WB group (p = 0.02). Severe neutropenia occurred more frequently in the PES group (27%) compared to the WB group (9.6%) (p = 0.002). CMV viremia occurred in 4.8% of the PES group compared to 2.4% of the WB group (p = 0.40), and CMV disease was diagnosed in 1.6% of the PES group compared to 2.5% of the WB group (p = 0.99). Other infections including urinary tract infection, bacteremia, or upper respiratory tract infections occurred in 11.3% of the Pescovitz group compared to 10.4% of the weight-based group (p > 0.99). More patients in the PES group (14.5%) received a G-CSF agent to treat neutropenia compared to the weight-based group (0.8%) (p = 0.0002).

*Conclusions: The incidence of neutropenia was greater in recipients receiving VGCV dosed via the PES algorithm compared to WB dosing. There were no differences in regards to CMV infection or disease.

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