Comparison of flow cytometry with the Sysmex XT2000iV automated analyzer for the detection of reticulated platelets in dogs.
BACKGROUND
Immature (reticulated) platelets (r-PLT) are not routinely assessed by hematology analyzers, but may be useful in the evaluation of the bone marrow response to thrombocytopenia.


OBJECTIVE
The aim of this study was to compare the Sysmex XT2000iV hematology analyzer with standard flow cytometry for the determination of r-PLT percentage in dogs.


METHODS
Blood samples were obtained from 40 healthy dogs, 12 thrombocytopenic dogs, and 6 dogs with normal platelet counts but with disorders associated with increased thrombopoiesis. The percentage of r-PLT was determined with a FACscan flow cytometer (r-PLT[F]) using CD61-phycoerythrin antibody and thiazole orange, and with the PLT-O channel of the Sysmex analyzer (r-PLT[S]). Mean platelet volume, platelet distribution width, and platelet large cell ratio were also determined on the Sysmex. Repeatability (intra-assay precision) and effect of storage were tested for the automated analyzer.


RESULTS
The reference interval (mean+/-1.96 X SD) for r-PLT(F) was 1.91+/-1.29% (range 0.78-3.68%) and for r-PLT(S) was 0.56+/-0.82% (range 0.11-2.16%). For both flow cytometry and the Sysmex, the patient group had a significantly higher mean percentage of r-PLT compared with the control group (P<.0001, unpaired Student's t-tests). Fair correlation (r=0.71; Spearman's regression analysis) was found for r-PLT results between the 2 methods, and a negative proportional systematic bias of -6.26 was found for the Sysmex (Bland-Altman analysis). Based on receiver operating characteristic curves and a cut-off of > or =0.975%, a sensitivity of 94.7% and a specificity of 85.7% were obtained for detecting r-PLT on the Sysmex, using flow cytometry as the reference method. Blood samples stored at 4 degrees C and 25 degrees C had a significant increase in the percentage of r-PLT after 24 and 48 hours, respectively.


CONCLUSIONS
The PLT-O channel of the Sysmex XT2000iV is capable of detecting immature platelets in healthy, thrombocytopenic, and non-thrombocytopenic ill dogs.
Pankraz
Alexander
A
Department of Veterinary Clinical Sciences, Clinical Pathology and Clinical Pathophysiology, Justus-Liebig University Giessen, Giessen, Germany. alexander_pankraz@lycos.de
Bauer
Natali
N
Moritz
Andreas
A
D000818:Animals; D004283:Dog Diseases / Q000097:blood; D004285:Dogs; D005260:Female; D005434:Flow Cytometry / Q000295:instrumentation / Q000662:veterinary*; D008297:Male; D019095:Point-of-Care Systems; D017701:Reticulocyte Count / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D012156:Reticulocytes / Q000166:cytology*; D013921:Thrombocytopenia / Q000097:blood / Q000662:veterinary