Evaluation of the immature platelet fraction contribute to the differential diagnosis of hereditary, immune and other acquired thrombocytopenias.

The differential diagnosis of immune (ITP) and hereditary macrothrombocytopenia (HM) is key to patient management. The immature platelet fraction (IPF) represents the subset of circulating platelets with higher RNA content, and has been shown to distinguish hypo- from hyperproliferative thrombocytopenias. Here we evaluated the diagnostic accuracy of IPF in the differential diagnosis between HM and other thrombocytopenias in a population of patients with post-chemotherapy thrombocytopenia (n = 56), bone marrow failure (n = 22), ITP (n = 105) and HM (n = 27). TPO levels were also measured in HM and ITP matched for platelet counts. Platelet counts were similar in all patient groups. Higher IPF values were observed in both ITP (12.3%; 2.4-65.6%) and HM (29.8%; 4.6-65.9%) compared to hypoproliferative thrombocytopenias. IPF values were also higher in HM compared to ITP, yielding a diagnostic accuracy of 0.80 (95%CI 0.70-0.90; P < 0.0001) to distinguish these two conditions. Intra- and inter-assays reproducibility of IPF in HM patients revealed that this is a stable parameter. In conclusion, IPF is increased in HM compared to both ITP and other thrombocytopenias and contributes to the differentiation between ITP and HM. Further studies are warranted to understand the biological rationale of these findings and to its incorporation in diagnostic algorithms of HM.

Performance of a point-of-care device in determining prothrombin time in supra-therapeutic INRs.

INTRODUCTION: Point-of-care (POC) devices have been widely adopted for monitoring prothrombin time (PT) (INR) following the demonstration of their accuracy compared to standard INR determination. However, guidelines suggest confirmation of POC results when INRs increase above therapeutic range, due to concerns regarding possible inferior performance of POC devices in high INR levels. Unfortunately, patients with supra-therapeutic INRs are underrepresented in studies that validated these devices. METHODS: We performed a prospective evaluation of the performance of a POC device in monitoring oral anticoagulation in patients with INR values above 3.5 in a University outpatient anticoagulation clinic. During a 6-month period, 2322 INR determinations were performed with a POC device, and results above 3.5 were immediately repeated on an automated coagulometer. RESULTS: Dual INR determinations by two methods were obtained in 160 visits, with a mean INR from the POC device of 4.52 ± 0.96. Both classical statistics and clinical concordance analysis yielded satisfactory results when the two methods were compared. CONCLUSION: Our results demonstrate that POC devices present good correlation with standard laboratory methods for PT determination in supra-therapeutic INRs and that differences in clinical management do not support the need for systematic confirmation of these results in nonbleeding patients.

Microparticles in deep venous thrombosis, antiphospholipid syndrome and Factor V Leiden.

Microparticles (MPs) are blebs released from cellular surfaces during activation/apoptosis. They are procoagulant, pro-inflammatory and could contribute to pathogenesis of deep venous thrombosis (DVT). This study compared the number, cellular origin and procoagulant activity of MPs on DVT patients in different clinical situations: at diagnosis (n = 9, 5F/4M; mean age = 41.11), 1-3 years after warfarin withdrawal (n = 10, 7F/3M; mean age = 32.90), associated to antiphospholipid syndrome (APS; n = 11, 9F/2M; mean age = 33.82), or asymptomatic carriers of Factor V Leiden (FVL; n = 7, 7F/0M; mean age = 34.00) vs healthy controls (CTR). The quantification and characterization were performed by flow cytometry using CD235, CD61, CD45, CD31, CD14, CD45, anti-TF and Annexin V. The plasmatic procoagulant activity was investigated by prothrombin fragment 1 + 2 (F1 + 2) determination. The MPs procoagulant activity was analyzed by D-dimer (DD2) and Thrombin Generation Test (TGT) on a healthy pool of plasmas adjusted or not by their number (10,000 MPs). The MPs percentages were not different between the groups, but absolute number was increased in patients 1-3 years after warfarin withdrawal vs CTR (P = 0.02). There was no difference of the MPs cellular origin comparing patients to controls. TGT using 10,000 MPs was lower on these patients (P = 0.01). APS patients showed a reduction of plasmatic procoagulant activity (P = 0.004), but they were under warfarin therapy. DD2 in the presence of MPs, independently of its number, was higher in patients with DVT at diagnosis (P < 0.0001). MPs of patients with spontaneous DVT at diagnosis can promote coagulation activation demonstrated by increased DD2. Even the increased MPs from patients 1-3 years after thrombotic episode generated lower amount of thrombin, they can have a protective effect by activation of Protein C anticoagulant pathway.