Prospective epidemiologic study of the outcome and cost-effectiveness of antenatal screening to detect neonatal alloimmune thrombocytopenia due to anti-HPA-1a.
BACKGROUND
To assess the value of antenatal screening to detect neonatal alloimmune thrombocytopenia (NAIT) due to anti-HPA-1a, a prospective study was carried out to quantify the potential clinical benefits and determine whether screening would be cost-effective.


METHODS
An observational prospective controlled study was carried out on 26,506 pregnant women over 2 years. HPA-1a phenotyping was performed in the first trimester and women confirmed HPA-1a-negative were tested for anti-HPA-1a during pregnancy, at delivery, and 10 to 14 days after birth. Babies of HPA-1a-negative women were tested at delivery for thrombocytopenia and examined for signs of bleeding. Economic evaluation was undertaken on the basis of the data collected during the study.


RESULTS
Twenty-five of 318 women (7.9%) had anti-HPA-1a detected for the first time. Eight women (43 per 100,000) gave birth to babies with NAIT, and 5 (27 per 100,000) had severe thrombocytopenia. Three babies had mild signs of bleeding, and no cases of intracranial hemorrhage (ICH) or fetal loss were detected. It is estimated that it would cost 60,596 pounds (98,771 US dollars) to detect a case of severe NAIT, where anti-HPA-1a has been identified for the first time, and 1,151,323 pounds (1,876,656 US dollars) to prevent a case of ICH, assuming that detection allowed successful intervention.


CONCLUSIONS
Our data suggest that severe HPA-1a NAIT is underdiagnosed in the absence of routine antenatal screening. Serious bleeding complications and ICH, however, occur less frequently in first cases of NAIT than suspected from the literature, and the costs of screening and possible intervention must be balanced against the procedural risks.
Turner
Marc L
ML
Scottish National Blood Transfusion Service, Aberdeen & Edinburgh, United Kingdom.
Bessos
Hagop
H
Fagge
Timothy
T
Harkness
Mairi
M
Rentoul
Frances
F
Seymour
Janelle
J
Wilson
David
D
Gray
Irene
I
Ahya
Ridheesh
R
Cairns
John
J
Urbaniak
Stan
S
D016824:Antigens, Human Platelet / Q000276:immunology*; D003362:Cost-Benefit Analysis; D003663:Decision Trees; D005260:Female; D006681:HLA-D Antigens / Q000276:immunology; D059826:HLA-DRB3 Chains; D006650:Histocompatibility Testing / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D039661:Integrin beta3; D007518:Isoantibodies / Q000097:blood; D010641:Phenotype; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D011296:Prenatal Diagnosis / Q000191:economics* / Q000706:statistics & numerical data; D011446:Prospective Studies; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000175:diagnosis* / Q000453:epidemiology* / Q000276:immunology; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D016036:Seroepidemiologic Studies
D016824:Antigens, Human Platelet; D006681:HLA-D Antigens; D059826:HLA-DRB3 Chains; C061248:ITGB3 protein, human; D039661:Integrin beta3; D007518:Isoantibodies