The Partial Absorption Test : A New Technique for Titrating Rh Antibodies of Pathological Significance

Abstract

SummaryA new test is described which enables the quantity of Rh antibody free in the fœtal serum to be estimated by titrations carried out on the maternal serum. Equal volumes of a hæmolysed 25% suspension of Rh‐positive red cells and a 1 : 4 dilution of the maternal anti‐Rh sera are incubated at room temperature for 15 minutes. The Rh antibody remaining free at the end of this time is titrated by the indirect antiglobulin method. The titre value obtained is referred to as the partial absorption (P.A.) titre.The P.A. titre is closely related to the titre of free Rh antibody in the cord serum of the infant at birth. The P.A. titre also is highly correlated with the blocking titre, but shows no relationship with the conglutination or albumin titres. The P.A. test, however, is more sensitive than the blocking test in detecting Rh antibodies of pathological significance, and is likely to be therefore of greater prognostic value.

Letter to the Editor

“…I n these cases antibody tests were carried out using both an ordinary indirect antiglobulin procedure, and also the P.A. test using the procedure outlined by VOS [4]. The authors conclude that "the Coombs technique is the most reliable for antenatal serology and the P.A.…”

Letter to the Editor

“…In these cases antibody tests were carried out using both an ordinary indirect antiglobulin procedure, and also the P.A. test using the procedure outlined by Vos [4]. The authors con clude that "the Coombs technique is the most reliable for antenatal serology and the P.A.…”

“…test introduced by Vos [4] for titrating Rh antibodies in maternal serum. The results presented in their paper and the conclusions drawn from them call for comment.…”

Hæmolytic Disease of the New‐born

“…However, the pathogenesis of hcemolytic disease almost certainly involves a number of factors, and it would be surprising if the severity of the disease depended solely on the titre of the maternal antibody, important though the titre may be. Vos (1958) has now proposed a further test, termed the "partial absorption (PA)" test, in which a measured quantity of the maternal serum is absorbed with an equal volume of a 25 % suspension of washed Rh-positive cells which have been hcemolysed by freezing. The remaining agglutinin is then titrated by the indirect Coombs method, and the result termed the "PA" titre.…”