Evaluation of Optical Refractometer for Assessing Failure of Transfer of Passive Immunity in Foals.

This study examines the effectiveness of an optical refractometer in determining whether newborn horses, or foals, have failed to receive critical immune support through their mother’s milk. Through examination of 30 foals, the study found a high correlation between measurements taken by the refractometer and concentration of Immunoglobulin G (IgG), a key immunity-boosting protein, suggesting the instrument’s value in assessing immune health in foals.

Research Methodology

• The research involves a sample of 30 foals from which blood was collected 12 hours after their birth.
• The total protein in the blood was measured using an optical refractometer, a device used to measure the amount of a substance in a solution.
• In parallel, the concentration of Immunoglobulin G (IgG), an important protein associated with the immune system, was determined using radial immunodiffusion (RID), a method used to measure the quantity of antibodies in a solution.
• Researchers also examined the correlation between the RID-measured IgG levels in the colostrum (the first milk produced by horses after birth, rich in antibodies) and the RID-measured IgG levels in the foals’ plasma.

Data Analysis and Results

• The data analysis method used is the ROC (receiver operating characteristic) curve, a tool used for diagnostic test evaluation. The ROC curve is created by plotting ‘true positive’ rate against ‘false positive’ rate.
• In this study, the ROC curve was used to identify the ideal cutoff point for total protein level using the optical refractometer to accurately diagnose the failure of passive transfer of immunity (FPTI).
• The researchers also assessed the sensitivity (ability of the test to correctly identify positive results) and specificity (ability of the test to correctly identify negative results) of the optical refractometer.
• The results of this analysis showed a strongly positive correlation between RID-measured IgG concentration and optical refractometer readings of total protein concentration, with a ROC curve value of 0.931 – an indicator of strong predictive ability. The optimal cutoff point was found to be ≤5.7g/dL with a sensitivity of 100% and specificity of 73.3%.

Conclusion

• The high correlation signifies that the optical refractometer can effectively diagnose FPTI in foals, meaning the device can be used to identify foals that may not have received an adequate amount of immunity through their mother’s milk.
• The research demonstrates that the total protein concentration measured by refractometer offers an easy, low-cost and sensitive method for evaluating FPTI in foals. It is practical for field use.