Serological and immunohistochemical diagnosis of amniotic fluid embolism

The purpose of this study was to evaluate whether serological assays and immunohistochemical staining, employing antibody TKH-2, are sensitive methods for the serological and histologic diagnosis of amniotic fluid embolism (AFE). TKH-2 is a sensitive antibody directed to sialyl Tn (STN), NeuAcalpha2-6GalNAc. Nineteen samples of maternal sera with clinical AFE and 120 control sera and 15 specimen of formalin-fixed, paraffin-embedded lung tissue sections were examined in this study. Tissue sections were stained using the streptavidin-biotin-immunoperoxidase method. The concentration of STN in serum was measured by an immunoradiometric competitive inhibition assay using the monoclonal antibody TKH-2 in a one-step procedure. Remarkable positive TKH-2 stainings were easily seen within the pulmonary vasculature in 14 of the 15 (93%) patients with AFE. The serum STN levels (mean+/-SD) in patients with AFE (110.8+/-48.1 U/ml) showed significantly higher concentrations compared with those of patients with non-AFE (17.3+/-2.6 U/ml) (p <0.01). Seventeen of 19 sera (89%) were diagnosed as AFE by serum TRH-2 level. We conclude that both TKH-2 immunostaining and serum STN assay are sensitive methods to diagnose patients with AFE.