ADVIA 2120 plateletcrit for assessing platelet status in cavalier king charles spaniels

Background: The plateletcrit method of the IDEXX VetAutoread hematology analyzer (QBC) is the best way to evaluate platelet status in dogs with very large platelets such as Cavalier King Charles Spaniels (CKCS) with macrothrombocytosis. It is unknown if Advia plateletcrit is accurate in CKCS. Objective: To test if the plateletcrit (A-PCT) of the Advia 2120 (Siemens Healthcare Diagnostics) could be used to evaluate platelet status in CKCS with and without macrothrombocytosis. Methods: Fresh EDTA blood samples from 43 CKCS in a study of myxomatous mitral valve disease were analyzed with Advia 2120 and compared with the QBC plateletcrit, which is reported as a platelet count (QBC PLT). Results: The number of CKCS considered thrombocytopenic varied with method. Advia PLT counts were under 150 x 109/L in 23 CKCS (53%), A-PCT was under preliminary reference values of 0.18-0.44 in 9 (21%) CKCS, while no CKCS had a QBC PLT count under 150 x 109/L. A-PCT agreed quite well with QBC (correlation r = 0.84), but appeared to underestimate PCT in CKCS with pronounced macrothrombocytosis. Conclusions: Advia plateletcrit should reflect the platelet status of dogs with large platelets fairly well but seem to underestimated plateletcrit in CKCS with pronounced macrothrombocytosis and thus overestimate how many CKCS that have decreased platelet volume. The Advia PCT is, however, much better than the platelet count to evaluate platelet status in dogs with macrothrombocytosis