Reducing error in feline platelet enumeration by addition of Iloprost to blood specimens: comparison to prostaglandin E1 and EDTA.

Background: Prostaglandin E1 (PGE1) and Iloprost inhibit platelet aggregation and should prevent or minimize preanalytic error with feline platelet enumeration.

Objectives: The objective was to compare the relative effectiveness in reducing errors in platelet enumeration by adding Iloprost to feline EDTA blood specimens in comparison to adding PGE1 or EDTA alone. In addition, a grading system for platelet aggregation in blood smears was evaluated for effectiveness in predicting prominent errors and compared to ADVIA's PLT-CLM flag. Finally, the use of plateletcrit in feline blood with platelet aggregation was evaluated.

Methods: Blood specimens from 35 cats were included. Blood was collected into EDTA tubes with or without Iloprost or PGE1, and was rapidly mixed. Platelet count (PLT), plateletcrit (PCT), mean platelet volume (MPV), and platelet flags were determined with an ADVIA 2120. Manual PLT was performed with a Leucoplate stain. PLT was determined by an IDEXX VetAutoread hematology analyzer (QBC).

Results: Neither addition of Iloprost nor PGE1 to EDTA blood specimens completely prevented platelet aggregation. Iloprost-treated specimens had the least severe aggregation. PGE1 was better than EDTA alone. Significant errors in PLT results were consistently identified by the grading system. ADVIA's PLT-CL flag usually predicted significant errors in PLT. QBC PLT results showed high imprecision. Manual PLT error was smaller than ADVIA PLT in EDTA specimens with aggregation.

Conclusions: Adding Iloprost to feline blood specimens improved platelet enumeration accuracy. A grading system for severity of platelet aggregation and usually the ADVIA's PLT-CL alarm predicted specimens with significant errors in platelet enumeration.