Incidence and Characteristics of Infections Following Cord Blood Stem Cell Transplantation in Children.

Infection is one of the most important causes of morbidity and mortality after hematopoietic stem cell transplantation. We assessed the incidence and characteristics of infections in 163 cord blood stem cell transplantation (CBT) recipients from 13 transplant centers of Korea between October, 1996 and April, 2005. The patients underwent CBT with standardized conditioning, GVHD prophylaxis and supportive care including pre-emptive ganciclovir therapy for cytomegalovirus (CMV) antigenemia. The median time to neutrophil engraftment was 19 days (10–62 days) and to platelet engraftment was 45 days (14–394 days). Within the post-transplant day 0 to day 30, 81.6% of patients (133/163) experienced febrile episodes with 11.7% (19/163) of clinically documented infection (CDI) and 19.6% (32/163) of microbiologically documented infection (MDI). The neutrophil engraftment was delayed in the patients with CDI and MDI rather than without CDI and MDI (day 26.3 vs day 21.5, P=0.03) before day 30. In the time period of day 30 to 100, febrile episodes, CDI and MDI occurred in 54.3% (82/151), 14.6% (42/151) and 13.2% (20/151), respectively. After day 100, 38.5% of patients (45/117) experienced febrile episodes with 17.9% (21/117) of CDI and 7.7% (9/117) of MDI. Although the incidence of febrile episodes before day 30 was significantly higher than after day 30, the incidence of CDI and MDI was comparable. There were no significant differences of infection rate according to the infused cell dose, the degree of HLA disparity, acute GVHD and chronic GVHD. The overall mortality rate after CBT was 40% (65/163). Infection was considered the primary cause of transplant-related mortality and represented 18.4% (106/163) of the causes of death with the median day of 96.5 (1∼1,081 days). The incidence of pre-transplant CMV-seropositivity was 85.5% of the patients (106/123) and CMV antigenemia developed in 52.7% of CMV-seropositive patients compared to 11.8% of CMV-seronegative patients (P=0.002). CMV disease developed in 25.7% of CMV-seropositive patients and 6.7% of CMV-seronegative patients, which showed statistiacally not significant. Pre-transplant conditioning regimens such as antithymocyte globulin did not affect on the incidence of CMV antigenemia or CMV disease. Based on our study, the infection was still the primary cause of mortality after CBT, particularly in patients with delayed neutrophil engraftment. The high prevalence of CMV seropositive patients in Korea was associated with increased incidence of CMV antigenemia, not with CMV disease.