Comparing red cell alloantibody detection and titration by gel microcolumn agglutination method with conventional tube in Rh-negative antenatal cases

Alloimmunization to red cell antigens during antenatal period is a serious complication. Antibody titration of maternal blood sample corroborates with severity of disease and helps in planning further management. Conventional Tube Testing (CTT) method is widely accepted for antibody titration in antenatal cases but it can be replaced by Gel Microcolumn Agglutination (GMA) as it offers many advantages. Critical titer levels have been recommended by CTT method, but corresponding levels by GMA are yet to be established due to lack of adequate data. Total of 1020 Rh negative antenatal females were evaluated over a period of four years and those found to be positive on antibody screening were further investigated. Antibody titration by CTT and GMA was carried out and the titers were correlated with the outcome of pregnancy. Out of the 1020 cases screened for antibodies, 112 (10.98%) were detected to be positive by GMA while 40 (3.92%) cases were detected by CTT. Titration was performed by both methods and results were statistically correlated. A moderate correlation was observed where one or more than one antibodies were involved (Pearson’s Coefficient 0.756), while a strong correlation (0.893) was observed between the two methods when single antibody (Anti-D) was involved. Titer values obtained by GMA were also higher than CTT. Gel microcolumn agglutination (GMA) was found to be more sensitive and precise method for titration. A titer of 512 by GMA (IgG only) mostly corresponded to the values of 16 by CTT and had good correlation with clinical outcome.