Modified stall-side crossmatch for transfusions in horses

Abstract

Background: After-hours or out-of-clinic crossmatches are often limited by the lack of access to specialized material and technical expertise.

Hypothesis/objectives: The goal was to adapt a stall-side crossmatch test for pretransfusion evaluation in horses.

Animals: Twelve healthy mares (plasma and blood donors, teaching mares).

Methods: In a prospective study, blood from 12 mares was used to compare the results of 132 crossmatches performed with a rapid gel assay to crossmatches performed with a microgel column assay, and with predicted compatibilities based on blood types and detection of antibodies at a reference laboratory (microplate assay). The rapid gel assay protocol for dogs was adapted to decrease the formation of rouleaux that initially precluded equine erythrocytes migration through the gel.

Results: There was a good agreement between the rapid gel assay and the microgel assay as well as with the predicted compatibilities (κ > .6 for both). Agreement was higher between the microgel assay and the predicted compatibilities (κ = .8). The rapid gel assay failed to detect 6 predicted Aa incompatibilities (agglutinins-related), 3 of which were also not detected with the microgel assay.

Conclusions and clinical importance: Based on these results, the modified rapid gel assay could be useful in settings when access to the microgel assay is not available. Discrepancies between both gel techniques and predicted compatibilities were most often low-grade agglutination, which warrants further investigation to assess their clinical importance.

Keywords: agglutination; blood transfusion; compatibility; equine.

Figure 1

Microgel and rapid gel grades. Agglutination grades for microgel assay (top panel) and rapid gel assay (bottom panel). 0: all erythrocytes passed through the gel and formed a compact pellet at the bottom, 1: most erythrocytes form a pellet at the bottom of the gel, but not compact, with few erythrocytes visible in the lower half of the gel, 2: erythrocytes are predominantly observed in the lower half of the gel column or are dispersed throughout the gel, 3: erythrocytes are dispersed on the top half of the gel with some retained on the gel surface, and 4: all erythrocytes are retained on top of the gel (here with some hemolysis in the microgel). Hemolysis (H) was considered present when red discoloration was observed in the microgel chamber (here with grade 4 agglutination) or in the gel itself for the rapid gel assay. In opposite to this rapid gel assay picture where only hemolysis can be appreciated, all 8 crossmatches in the current study with detectable hemolysis also resulted in positive agglutination (both with the rapid gel and microgel assays). Crossmatches with hemolysis or grades ≥2 agglutination were considered incompatible. For the top panel (microgel) grades 4 and H come from clinical cases of neonatal isoerythrolysis

Figure 2

Preliminary study. The incubation solution from the microgel protocol when looked under a microscope showing scattered red blood cells (A). The incubation solution of the rapid gel assay with the original canine protocol showing extensive rouleaux formation (B) and positive (incompatible) auto‐controls (C). Scale bar = 80 μm

Figure 3

Grade agreement between microgel and rapid gel assays. One hundred thirty‐two crossmatches between the plasma (microgel) or serum (rapid gel) of 11 horses and the erythrocytes of 12 horses. In each section, dots were spread out within the appropriate grade to avoid overlap. Grades highlighted in blue (0 and 1) are considered compatible and grades in red (2‐4) are considered incompatible. Any diagonal line between 2 dots represents a discrepancy of grade and lines crossing between the blue and red sections represent a discrepancy of compatibility between the 2 tests. Agreement between the rapid gel and the microgel assays was good for compatibility (κ = .62) but slight for grades (weighted κ = .40)