Assessment of plasma anti-elastin antibodies for use as a diagnostic aid for chronic progressive lymphoedema in Belgian Draught Horses.

This study assesses the efficacy of using antibodies against elastin, a protein in the skin, as a diagnostic tool for Chronic Progressive Lymphoedema (CPL) in Belgian Draft Horses. However, despite higher levels of these antibodies in horses with severe CPL, significant overlap with healthy horses and low test sensitivity limit the test’s diagnostic utility.

Research Context

• Chronic Progressive Lymphoedema (CPL) is a disease that primarily affects draught horses, including the Belgian Draught Horse. It is generally diagnosed by observing lesions on the lower limbs of the animal.
• Elastin, a protein in the skin and the subcutaneous tissue, has been suggested to be involved in the pathology of CPL. When it degrades, it can trigger the generation of antibodies against elastin (AEAb), which can be detected in horse serum using an ELISA (enzyme-linked immunosorbent assay) test.
• Earlier tests demonstrated lower average AEAb levels in healthy horses compared to horses with symptoms ranging from mild to severe CPL. Consequently, this study aimed to validate the AEAb-ELISA procedure as a diagnostic tool for CPL.

Research Methodology

• For the validation of the AEAb-ELISA test, 345 draft horses were studied, and the tests were carried out independently in two different laboratories.
• Factors that could potentially influence AEAb-levels, such as the horse’s age, gender, pregnancy status, the laboratory conducting the tests, and the date of blood collection, were analyzed using a mixed statistical model.

Research Findings

• The study discovered that the AEAb test results were reproducible regardless of which laboratory carried out the tests.
• Horses moderately or severely impacted by CPL possessed considerably higher levels of AEAb than healthy ones. However, the study noted this was only evident in barren mares, female horses that are not pregnant.
• There was a large overlap in AEAb-levels between the different clinical groups, which complicates the diagnosis accuracy. Furthermore, a reasonably high AEAb cut-off ensured a specificity of 90%, but only a sensitivity of 21%—an indication that the test may produce many false negatives.

Conclusion

• The study concludes that, due to the significant overlap of AEAb-levels in both healthy and CPL-affected horses and the low test sensitivity, the AEAb-ELISA procedure is not a useful diagnostic test for CPL in individual horses.