Reticulated Platelets Quantification In An Automatic CBC Counter and Its Role In Thrombocytopenia Etiology Assessment

Reticulated platelets (rP) are young platelets, recently released from the bone marrow, and contain more cytoplasmic RNA elements than mature platelets. Considerable amount of evidence suggests that rP analysis may be useful in the investigation of platelet disorders. Automatic quantification methods have been developed; however, the methodology has not yet been standardized and validated in clinical practice.

To analyze the rP percentage (rP%) in 168 samples, using software version v3 in Cell Dyn® Sapphire, in correlation with clinical data.

168 samples analyzed in Cell Dyn® Sapphire, between March and August 2010, using CBC+RET methodology in the determination of: rP%, reticulocytes % (Ret%), platelet optical counts (PLTo) and mean platelet volume (VPM). Normal control samples (C) n=73; Patients: 20 with auto-immune haemolytic anemia (IHA); 8 with thrombocytopenic thrombotic purpura (TTP); 45 with immune thrombocytopenia (IT), 4 with bone marrow aplasia (BMA) and 18 thrombocythopenias of unknown cause (TUC). Mean difference between rP% in controls vs TUC samples calculated by t-student. Statistical analysis by StatView 5.0.

C samples: median rP % =1.6, range=0.2-4.1, mean PLTo= 263×10⁹/L, median MPV=8.5fL. IHA: median rP%= 1.9, range =0.6 – 12.5, mean PLTo=284×10⁹/L, median MPV= 8.6, mean Ret%=12. TTP: median rP%=5.1, range=0.3-16.5, mean PLTo=185×10⁹/L, median MPV=8.5. IT: median rP%=3.8, range=0.4-27.8, mean PLTo=56.8×10⁹/L, median MPV=11.4. BMA: median rP%=4.1, range=0.3-6, mean PLTo=66.2×10⁹/L, median MPV=11. TUC: median rP%=2.7, range=0.2-13.6, mean PLTo= 80.5×10⁹/L, median MPV=11.1 Mean difference between rP% in C vs TUC samples: t=2.5, p=0.02.

Median rP% values obtained in control group are in agreement with published data, despite the variation in the “normal” values between the authors. MPV and rP% in destructive thrombocytopenias (IT and TTP) are higher than in control group, in accord to immature platelets release by the bone marrow. IHA patients, despite the high Ret%, have a median rP% similar to the control group, demonstrating that rP counts are not over-estimated by the high number of reticulocytes. In BMA rP% is higher than expected, however the number of samples analyzed is very low. The statistically significant mean difference between rP% in Control vs TUC samples makes the immune cause for the thrombocytopenia very likely. Due to its simplicity, ready availability and information provided by this methodology, it has a good potential to be a useful tool in the investigation of thrombocytopenias of unknown cause.

No relevant conflicts of interest to declare.