Comparison of hemagglutination and solid phase titration methods for determination of critical prenatal antibody titers

The hemagglutination (HA) tube method is the standard method for determination of antibody titer in prenatal samples. Most facilities use a titer between 8 and 32 as their definition of a critical value when amniocentesis may be considered. This study determined if there is a relationship between the results of HA tube and solid phase (SP) titers performed on the same sample. Forty-six paired samples containing known antibody were titrated by both HA tube and SP methods and the results subjected to data analysis. We conclude that there is a strong correlation between HA tube and SP methods in titer end points; i.e., SP was greater than or equal to HA in every case. In addition, the appropriate critical SP titer is 64, which is at least equivalent to an HA critical titer of 16. Immunohematology 1997;13:84–89.