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 -/-).