Neonatal alloimmune thrombocytopenia in the Irish population: a discrepancy between observed and expected cases.
OBJECTIVE
To estimate the rate of detection of neonatal alloimmune thrombocytopenia (NAITP) in the Irish population, to investigate clinical presentation and outcome in affected infants, and to determine the extent, if any, to which this condition is underdiagnosed at present.


METHODS
Cases were collected in a retrospective fashion from a review of platelet serology laboratory records from January 1992 to December 2000. Clinical data were obtained from hospital records. Testing for maternal antiplatelet antibody was by one or more of the following: the platelet suspension immunofluorescence test, a commercial antigen capture enzyme linked immunosorbent assay (GTI-PakPlus), and the monoclonal antibody immobilisation of platelet antigens assay. Platelet antigen typing was by the polymerase chain reaction technique with sequence specific primers.


RESULTS
Twenty seven serologically verified cases of NAITP were identified in 18 families. Maternal antibody to human platelet antigen 1a accounted for 25 of the 27 confirmed cases. Twenty one of 26 infants were born with severe thrombocytopenia. Nineteen of 27 infants had bleeding manifestations at birth. Petechiae and bruising were most commonly observed (n = 17). There were no documented cases of intracranial haemorrhage in this group but systematic cranial ultrasound was not performed.


CONCLUSIONS
Screening studies in predominantly white populations have estimated the incidence of NAITP to be between 1 in 1000 and 1 in 2000 live births. With 50 000 births each year in Ireland, these results give a clinical detection rate for NAITP of just 1 case in 16 500 live births, strongly suggesting that NAITP is currently underdiagnosed. Antenatal screening to detect women at risk of having babies with NAITP is now scientifically feasible and should be considered.
Davoren
A
A
Irish Blood Transfusion Service, National Blood Centre, James's Street, Dublin 8, Ireland. annedavoren@eircom.net
McParland
P
P
Barnes
C A
CA
Murphy
W G
WG
D016824:Antigens, Human Platelet / Q000097:blood / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology; D005260:Female; D006470:Hemorrhage / Q000276:immunology; D006801:Humans; D007112:Immunity, Maternally-Acquired; D015994:Incidence; D007231:Infant, Newborn; D039661:Integrin beta3; D007494:Ireland / Q000453:epidemiology; D007518:Isoantibodies / Q000097:blood; D010976:Platelet Count; D011247:Pregnancy; D012189:Retrospective Studies; D013921:Thrombocytopenia / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology
D016824:Antigens, Human Platelet; C061248:ITGB3 protein, human; D039661:Integrin beta3; D007518:Isoantibodies