According to a recently published study in Transfusion, the automated solid phase (ASP) method appears to be superior to the traditional manual tube saline indirect antiglobulin testing (SIAT) for clinical monitoring of hemolytic disease of the fetus and newborn (HDFN).
HDFN is caused by maternal antibodiesAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. that target fetal red blood cells, destroying them and causing complications such as severe anemiaAnemia A condition that occurs when the body doesn’t have enough healthy red blood cells to carry oxygen to its tissues. In HDFN, anemia occurs when maternal antibodies destroy fetal red blood cells.. AntibodyAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. screening helps detect pregnancies at risk of developing HDFN, thus constituting an important part of prenatal monitoring.
The results of these tests are more complex than a simple positive or negative, as complications derived from maternal antibodies only occur above a certain level of antibodies in the blood; this level is known as critical titer. Using the currently preferred method SIAT, the critical titer is above 16.
Learn more about HDFN testing and diagnosis
“While SIAT is considered the gold standard method for determining perinatal antibody titers, this method has some disadvantages: It is a manual test that is both time- and resource-intensive and requires a skilled technologist to both perform and interpret the test,” the authors wrote.
New methods such as ASP could overcome the disadvantages associated with SIAT. However, the critical antibody titer for many of these tests remains unknown. Therefore, the authors aimed to compare SIAT and ASP antibody titers in the same patients to determine which ASP titer is equivalent to a 16 SIAT titer.
The study used over 150 frozen plasma samples from blood donors as well as from prenatal patients, of which 78 had antibodies associated with HDFN. In the majority of samples, the AST titer was greater than the SIAT titer.
Results showed a critical titer value of 32 would be the appropriate ASP value, suggesting a high risk of HDFN complications. The method also proved to be more time efficient and more effective than SIAT.
However, in light of the risks associated with false negative results, the authors recommend performing more research before substituting SIAT as the standard for prenatal monitoring in cases with multiple antibodies capable of causing HDFN.
“Due to the potentially significant clinical consequences of a false-negative result, cases with multiple antibodies should continue to be tested and reported using the SIAT method,” the authors wrote.
