title: Predictors of low haematocrit among repeat donors in São Paulo, Brazil: eleven year longitudinal analysis.
abstract: OBJECTIVE
  Few longitudinal studies have examined the long-term effect on deferral for low haematocrit (Hct) or haemoglobin, indicators of presence of anaemia. This study retrospectively analysed 11 years of donation history to examine predictors related to such deferrals among repeat blood donors.
  
  
  METHODS
  We included 385,357 donors with at least two visits to the blood centre between January 1996 and December 2006 who were not deferred due to haematocrit at their first visit. We evaluated variables related to the development of low Hct (LHct-below 38% for females and 39% for males) after whole blood donations.
  
  
  RESULTS
  Over the 11-year period, 3,850 (1.5%) of the 252,301 males and 18,104 (13.6%) of the 133,056 females were deferred due to LHct at some point after their first donation. Genders, age, baseline Hct, Hct at the visit immediately before deferral due to LHct, and interval between donations, were associated with higher rates of development of LHct in repeat donors.
  
  
  CONCLUSIONS
  Our analysis showed that deferral due to low Hct levels in repeat blood donors is highly prevalent in Brazil. Assigning longer donations intervals based on the Hct levels at the qualifying donation or supplementing iron to donors at risk may decrease deferral rate of donors with low Hct.
authors.affiliation: Laboratório de Banco de Dados, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Fernanda N
authors.initials: FN
authors.lastname: Almeida
authors.forename: Ester C
authors.initials: EC
authors.lastname: Sabino
authors.forename: Gisela
authors.initials: G
authors.lastname: Tunes
authors.forename: George B
authors.initials: GB
authors.lastname: Schreiber
authors.forename: Pedro Paulo S B
authors.initials: PP
authors.lastname: da Silva
authors.forename: Anna Barbara F
authors.initials: AB
authors.lastname: Carneiro-Proietti
authors.forename: João Eduardo
authors.initials: JE
authors.lastname: Ferreira
authors.forename: Alfredo
authors.initials: A
authors.lastname: Mendrone
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000453:epidemiology; D001782:Blood Donors / Q000706:statistics & numerical data*; D001938:Brazil / Q000453:epidemiology; D005260:Female; D006400:Hematocrit / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D055815:Young Adult
keywords: Anaemia; Blood donation; Blood donors; Haematocrit; Qualifying donation