1075. Absolute Lymphocyte Count as a Predictor of Cytomegalovirus (CMV) Infection and Recurrence in Hematopoietic Stem Cell Transplant (HSCT) Recipients

BACKGROUND: Cytomegalovirus (CMV) is a serious complication following Hematopoietic Stem Cell Transplant (HSCT) and can lead to serious organ disease and mortality. This study aimed to investigate the association between absolute lymphocyte count (ALC) and CMV to determine whether ALC could help to identify those at an increased risk of CMV infection and recurrence METHODS: Adults undergoing HSCT between 2011 and 2016 at Rigshospitalet, Denmark were included. Cox proportional hazards models investigated risk factors, including ALC, for CMV infection in the first year post-transplant and recurrent CMV infection 6 months after clearance and stopping CMV treatment for the first infection. For the primary outcome ALC was investigated as a time-updated risk factor lagged by 7 days, and for recurrent CMV, ALC measured at the time at the time of stopping treatment for the first CMV infection was investigated (+/- 7 days). RESULTS: Of the 352 HSCT recipients included, 57% were male, 40% received myeloablative conditioning, 42% had high risk (D-R+) CMV IgG serostatus at transplant and the median age was 56 (IQR 43-63). 143 (40.6%) patients had an episode of CMV DNAemia a median of 47 days after transplant (IQR 35-62). A lower current ALC (≤ 0.3 x10(9)/L) was associated with a higher risk of CMV infection in univariate analysis compared to a high current ALC (> 1 x10(9)/L). However, this association was attenuated after adjustment, particularly for acute graft versus host disease (Figure). 102 HSCT recipients were investigated for risk of recurrent CMV of which 41 (40.2%) had a recurrent CMV episode a median of 27 days (IQR 16-50) after stopping CMV treatment for the first infection. A lower ALC (≤ 0.3 x10(9)/L) at the time of stopping CMV treatment was associated with a significantly higher risk of recurrent CMV after adjustment (Figure). A higher peak viral load (> 1500 IU/ml) during the first episode of CMV infection was also associated with an increased risk of recurrent CMV (aHR 2.47, 95%CI 1.00-6.10 compared to < 750 IU/ml). Association between absolute lymphocyte count (ALC) and risk of CMV infection and recurrent CMV within 6 months. **First CMV infection multivariable model also adjusted for sex, CMV serostatus, age, year of transplant, Charlson Comorbidity Index, Anti-thymocyte globulin (ATG) given, HLA donor-recipient matching, and acute graft versus host disease (time-updated) *Recurrent CMV infection multivariable model also adjusted for conditioning regimen, sex, CMV serostatus, age, year of transplant Anti-thymocyte globulin (ATG) given, HLA donor-recipient matching, and acute graft versus host disease and peak CMV viral load during the first CMV infection CONCLUSION: A lower ALC at the time of stopping treatment for the first CMV infection was associated with an increased risk of recurrent CMV and could be used to help guide decisions for augmented CMV surveillance and clinical awareness of CMV disease symptoms in these patients. [Image: see text] DISCLOSURES: All Authors: No reported disclosures