title: HPA-5b (Bra) neonatal alloimmune thrombocytopenia in Quebec: incidence and clinical outcome in 31 cases.
abstract: BACKGROUND
  Clinical detection of neonatal allo-immune thrombocytopenia (NAITP) is often less than the incidence predicted in prospective studies. The aims of this study were to calculate the observed and expected incidence of NAITP in Quebec, Canada, and to evaluate the clinical outcome of infants with anti-HPA-5b NAITP.
  
  
  METHODS
  Records from 1998 to 2002 of the only PLT serology laboratory for the province of Quebec were reviewed, as were hospital charts of all HPA-5 cases. The number of expected NAITP cases was estimated with known alloantigen gene frequencies.
  
  
  RESULTS
  Ninety cases of NAITP were identified. The clinical detection rate was 1 in 4100, with 9 to 30 percent of expected HPA-1a and 11 to 23 percent of expected HPA-5b NAITP cases detected. Seventy-eight percent of cases of HPA-5b NAITP were asymptomatic. Sixty-three percent of all deliveries but 94 percent of HPA-5b cases occurred in hospitals performing cord blood PLT counts.
  
  
  CONCLUSIONS
  The NAITP detection rate was 25 to 50 percent of the rate reported in prospective trials. The less severe clinical presentation of NAITP owing to HPA-5b was confirmed. The frequent routine determination of cord blood PLT counts may explain increased detection of asymptomatic NAITP involving anti-HPA-5b.
authors.affiliation: Héma-Québec, Montreal, Quebec, Canada. julie.rousseau.hsc@ssss.gouv.qc.ca
authors.forename: Julie
authors.initials: J
authors.lastname: Rousseau
authors.forename: Mindy
authors.initials: M
authors.lastname: Goldman
authors.forename: Michèle
authors.initials: M
authors.lastname: David
mesh_terms: D000328:Adult; D016824:Antigens, Human Platelet / Q000276:immunology*; D005260:Female; D005312:Fetal Blood / Q000166:cytology / Q000276:immunology; D005787:Gene Frequency; D006801:Humans; D007112:Immunity, Maternally-Acquired; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use; D007231:Infant, Newborn; D007518:Isoantibodies / Q000276:immunology*; D008297:Male; D015997:Neonatal Screening; D011247:Pregnancy; D011792:Quebec / Q000453:epidemiology; D012008:Recurrence; D012189:Retrospective Studies; D013921:Thrombocytopenia / Q000151:congenital* / Q000453:epidemiology / Q000235:genetics / Q000276:immunology / Q000628:therapy; D016896:Treatment Outcome
chemical_list: C055973:5b alloantigen, human; D016824:Antigens, Human Platelet; D016756:Immunoglobulins, Intravenous; D007518:Isoantibodies