Variables
The primary outcome variable was QoL, evaluated at a minimum of two years post-transplant. We assessed this using the PedsQL TM 4.0 questionnaire tool. This tool is reliable and valid in children who are healthy, ethnically diverse, or diagnosed with acute and chronic disease.23,24 It is composed of 23 items that gauge function in the following four areas: physical functioning (eight items), emotional functioning (five items), social functioning (five items), and school functioning (five items). Overall functioning was also recorded as an average of the four individual scores. Patients reported their function using a 5-point Likert scale ranging from 0 (never) to 4 (almost always). These responses were reverse scored and linearly transformed to a 0 to 100 scale, with a higher score indicating higher QoL. The median time between date of transplant and date of most recent PedsQL TM 4.0 completion was 2.98 years (range: 2–15 years). Other variables of interest obtained from medical records included: sex (male or female); race (non-Hispanic White [referred to as White], Hispanic, non-Hispanic Black [referred to as Black], or Native American); and age at transplant.
Patient socioeconomic status was estimated using the following variables: insurance status (state/federally-funded insurance or private insurance) and median household income (> $50,000 or < $50,000, estimated based on median income at patient’s billing zip code per the United States Census Bureau).25,26
Transplant-related variables included age and date at first HSCT; type of diagnosis (malignant or non-malignant); conditioning regimen (myeloablative or reduced intensity); donor type (matched related, unmatched related, or mismatched unrelated); donor source (bone marrow, peripheral/circulating blood, or cord blood); and donor and recipient cytomegalovirus (CMV) status (donor/recipient: +/+, +/-, -/+, or -/-).