Peer-reviewed veterinary case report
How diluting dog blood samples improves immune hemolysis test accuracy
By Sun, Prudence L & Jeffery, Unity·Published in Journal of veterinary internal medicine·2020·College of Veterinary Medicine and Biomedical Sciences, United States·View original on PubMed →
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Original publication title: Effect of dilution of canine blood samples on the specificity of saline agglutination tests for immune-mediated hemolysis.
- Species:
- dog
Plain-English summary
A group of 150 dogs with low red blood cell counts was tested for immune-mediated hemolytic anemia (IMHA), a condition where the immune system attacks red blood cells. The tests used were saline agglutination tests (SATs), which showed a high rate of false positives when diluted at a 1:1 ratio. However, when the blood was diluted at a 49:1 ratio with saline, the tests became much more accurate, correctly identifying IMHA in most cases. This means that using a higher saline dilution can help vets make better diagnoses and avoid unnecessary treatments.
People also search for: dog anemia symptoms · immune-mediated hemolytic anemia treatment · saline agglutination test for dogs
Abstract
BACKGROUND: Saline agglutination tests (SATs) are widely recommended for diagnosis of immune-mediated hemolytic anemia in dogs, but there are frequent false-positive results. OBJECTIVES: Specificity of SATs will improve at higher saline-to-blood ratios. ANIMALS: One hundred fifty dogs treated at a veterinary referral hospital with hematocrits ≤30%. METHODS: Prospective diagnostic accuracy study. Immune-mediated hemolysis (IMH) was considered present if a gel direct antiglobulin test (DAT) was positive and there was clinical evidence of hemolysis (n = 9), absent if another mechanism for anemia was identified and the DAT was negative or there was no hemolysis (n = 138), and if IMH status was unclear, dogs were excluded (n = 3). Saline agglutination tests were prepared at 1 : 1, 4 : 1, 9 : 1, and 49 : 1 saline-to-blood ratios, and microscopic agglutination was considered a positive result. RESULTS: Specificity for IMH increased from 29% (95% confidence interval 20-38) at a 1 : 1 dilution to 97% (93-99) at a 49 : 1 dilution. Sensitivity was 88% (47-100) at 1 : 1 and 4 : 1 dilutions and 67% (30-93%) at 9 : 1 and 49 : 1 dilutions. Diagnostic accuracy increased from 33% (24-42) at 1 : 1 dilution to 95% (90-98) at 49 : 1 dilution. CONCLUSIONS AND CLINICAL IMPORTANCE: If performed using a 49 : 1 saline-to-blood ratio, SATs achieve high specificity for IMH. Based on a gold standard of positive DAT and evidence of hemolysis, lower saline-to-blood ratio results should not be used because false-positive results are common.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/33169867/