Analytical Validation of MINI-PET as Point-of-Care for Erythrocyte Sedimentation Rate Measure in Horses

The erythrocyte sedimentation rate (ESR) is a widely used diagnostic assay in human medicine but nowadays poorly applied in veterinary medicine. This test measures the speed (millimeters per hour) at which red blood cells settle in a whole anticoagulated blood tube. In human medicine, high ESR values are associated with various disorders, including infections, rheumatoid arthritis, oncologic diseases, and other inflammatory conditions. The ESR can also be influenced by some factors such as age and gender. In veterinary medicine, the ESR with the Westergren manual method was almost forgotten over the years due to blood consumption and long turn-around time. The instrument MINI-PET, using a modified Westergren method, does not require blood consumption or release waste product and recently has been applied in canine medicine. The aims of the study in the horse were as follows: to establish the appropriate time to read the ESR with the Westergren reference method; to compare the MINI-PET ESR results with the reference technique; to assess the ESR reference intervals with MINI-PET; and to establish the ESR stability from collection at different time points by MINI-PET. Using 150 horses, we established 60 minutes as the appropriate time for ESR reading with the Westergren method. Moreover, ESR results obtained in 8 minutes with MINI-PET showed a good correlation with the Westergren ESR. Reference intervals (RIs) with MINI-PET were established in mm/h for the healthy horses (geldings 18.6-100.1; stallions, 13.8-55.7; and mares 1-73.7) according to the American Society of Veterinary Clinical Pathology guidelines. In addition, the ESR stability from the blood collection time was evaluated in the MINI-PET on 15 horses: at room temperature, ESR is stable up to 8 hours and at 4°C up to 24 hours. In conclusion, MINI-PET represents a rapid and reliable tool for measuring ESR in horses, offering a valid option to replace the traditional manual technique.