Validation of a cage-side agglutination card for Dal blood typing in dogs

Abstract

Background: Although 98% of the canine population is Dal-positive, Dal-negative dogs are more common in some breeds such as Doberman Pinschers (42.4%) and Dalmatians (11.7%), and finding compatible blood for these breeds may be challenging, given limited access to Dal blood typing. Objectives: To validate a cage-side agglutination card for Dal blood typing and determine the lowest packed cell volume (PCV threshold) at which interpretation remains accurate. Animals: One-hundred fifty dogs, including 38 blood donors, 52 Doberman Pinschers, 23 Dalmatians and 37 anemic dogs. Three additional Dal-positive canine blood donors were included to establish the PCV threshold. Methods: Dal blood typing was performed on blood samples preserved in ethylenediaminetetraacetic acid (EDTA) <48 hours using the cage-side agglutination card and a gel column technique (gold standard). The PCV threshold was determined using plasma-diluted blood samples. All results were read by 2 observers, blinded to each other's interpretation and to the sample's origin. Results: Interobserver agreement was 98% and 100% using the card and gel column assays, respectively. Overall, the sensitivity and specificity of the cards were 86%-87.6% and 96.6%-100%, respectively, depending on the observer. However, 18 samples were mistyped using the agglutination cards (15/18 by both observers): 1 false-positive (Doberman Pinscher), and 17 false-negative samples including 13 anemic dogs (PCV range, 5%-24%; median, 13%). The PCV threshold allowing reliable interpretation was determined to be >20%. Conclusions and Clinical Importance: Dal agglutination cards are reliable as a cage-side test, but results should be interpreted cautiously in severely anemic patients.