Can serological methods help distinguish between prophylactic and alloimmune anti-D?

Area of Science:

• Immunohaematology
• Transfusion Medicine
• Serology

Background:

• Distinguishing prophylactic from alloimmune anti-D is vital for RhD-negative pregnant women.
• Current methods rely on patient history and serological scoring.
• A specific test for alloimmune anti-D can improve diagnostic accuracy.

Purpose of the Study:

• To evaluate the enzyme indirect antiglobulin test (EIAT) and polyethylene glycol IAT (PIAT) for differentiating anti-D sources.
• To compare EIAT and PIAT against the standard low ionic strength solution-IAT (LISS-IAT).

Main Methods:

• Tested 273 plasma samples from antenatal, preoperative, and postmenopausal individuals.
• Utilized column agglutination testing (CAT) for initial anti-D identification.
• Compared tube LISS-IAT, EIAT, and PIAT, calculating agglutination score differences.

Main Results:

• EIAT showed a significant increase in agglutination score for alloimmune anti-D samples compared to LISS-IAT.
• EIAT demonstrated 59% sensitivity, 100% positive predictive value, and 100% specificity for alloimmune anti-D.
• 32% of alloimmune anti-D samples showed a +2 or +3 score increase with EIAT.

Conclusions:

• EIAT can confirm the presence of alloimmune anti-D when detected in routine screening.
• EIAT is not sufficient to exclude alloimmune anti-D.
• Further development may enhance EIAT's utility in differentiating anti-D antibody origins.