Maja Tomicic
Croatian Institute of Transfusion, Croatia
Title: Fetal and neonatal alloimmnune thrombocytopenia (FNATP): frequency, pathophysiology and algorithm of laboratory investigation and treatment
Biography
Biography: Maja Tomicic
Abstract
Background:
Alloimmune fetal and neonatal thrombocytopenia (FNATP) is the result of maternal alloimmunization during pregnancy to fetal platelet antigens (HPA) inherited from the father.
In most cases develops consequently to alloimmunization to the specific platelet antigens (HPA)-1a and-5b, less frequently HPA-3a and -15a/b. FNATP has an incidence of 1:1000 to 1:2000 births in white populations. It is self-limiting and transient disorder with an excellent prognosis in absence of intracerebral bleeding (ICH). Current guidelines recommended transfusion of HPA compatibile platelets to prevent ICH.
Aim:
The aim of this study was to established an algorithm of laboratory testing for FNATP and to analyze laboratory and clinical data on platelet transfusions in anti-HPA-1a cases.
Methods:
An algorithm of laboratory testing for FNATP included serologic screening of maternal and neonatal sera/plasma and platelets by immunofluorescence (IF) method; direct and indirect test. The monoclonal antibody immobilization of platelet antigens (MAIPA) and PAK 12-KIT (Lifecodes/Immucor, USA) were employed to determine anti-HPA antibody specificity. Results of serologic anti-HPA testing were confirmed by maternal and neonatal/paternal HPA-1, -2, -3, -5 and -15 genotyping by PCR-SSP method.
Results:
Serology screening for FNATP yielded positive results in of 56 of investigated cases. Anti-HPA antibodies were detected in 34 of 56 (61%) cases of serologically positive NATP, i.e. 19 anti-HPA-1a, 11 anti-HPA-5b, 1 antiHPA-1b, 1 antiHPA-3a, 1 antiHPA-5a and 1 anti-HPA-15a. In 6 of 56 (11%) pan-reactive (anti GP IIb-IIIa) autoantibodies in mothers with ITP were detected. In another 16 of 56 (28%) cases, anti-HPA specificity could not be demonstrated.
The average lowest platelet count in newborn blood was 60x 109/L (min.11 and max.104) and duration of thrombocytopenia 1,5 weeks (min. 0,5 and max. 3). 14 of 16 (87%) neonates did not receive any treatment and there were no signs of hemorrhage. One newborn received platelet transfusions, intravenous gamma globulins and corticoids, and another tree transfusions and intravenous gamma globulins. All of them reached full recovery. There was no fatal disease.
Conclusion:
FNATP is rare but potentially life-threatening disorder. Serologic testing for FNATP in case of isolated thrombocytopenia in the newborn contributed considerably to timely detection of this disease. Platelet transfusions are needed in severe cases of FNATP to prevent ICH
In the absence of HPA compatibile platelets random donor transfusion is an acceptable approach in urgent situations.