Platelet volume parameters as a diagnostic tool: the influence of anticoagulation and storage conditions on platelet impedance volume

Mean platelet volume in arterial and venous thrombotic disorders

The mean platelet volume (MPV) is an easy, rapid and inexpensive laboratory parameter which basically mirrors platelet size. Due to the essential role of platelets in hemostasis, many studies have assessed the MPV value in patients with arterial and venous thrombotic disorders. These have then been summarized in some interesting meta-analyses and recent studies that will be discussed in this narrative review. Taken together, the currently available evidence suggests that the MPV may be substantially increased in concomitance with acute episodes of coronary artery disease, venous thromboembolism, portal vein thrombosis, stroke, erectile dysfunction and preeclampsia. In many of these conditions, an increased MPV value may also be associated with unfavorable outcomes. Despite these convincing findings, some important technical issues should be considered for improving the clinical usefulness of this measure. These essentially include anticoagulant, timing of sample collection, the sample storage conditions, the influence of the analytical techniques, the approaches used for its calculation, the accurate definition of reference ranges and diagnostic cut-offs, as well as the current lack of standardization, which makes data obtained with different techniques/analyzers poorly comparable. Provided that the impact of these variables can be abated or minimized, the MPV can gain a valuable role in the laboratory workout of many arterial and venous thrombotic disorders.

Blood cells attachment after root conditioning and PRP application: an in vitro study

AIM

Root conditioning is aimed at smear layer removal and at dental matrix collagen exposure, which may promote periodontal regeneration. This in vitro study assessed smear layer removal, collagen fiber exposure and the influence of PRP (platelet-rich plasma) application on adhesion of blood cells to the root surface using scanning electron microscopy (SEM).

MATERIALS AND METHODS

Scaled root samples (n = 160) were set in five groups and conditioned with: group I - control group (saline solution); group II (EDTA 24%); group III (citric acid 25%); group IV (tetracycline hydrochloride 50 mg/ml); group V (sodium citrate 30%). Eighty samples were assessed using the root surface modification index (RSMI). The other eighty samples were set in two groups. The first group (n = 40) received PRP gel application with a soft brush and the second group (n = 40) received PRP application and then a blood drop. The fibrin clot formation was assessed in the first group and the blood cells adhesion was assessed in the second group using the BEAI (blood elements adhesion index). A previously trained, calibrated, and blind examiner evaluated photomicrographs. Statistical analysis was performed using the Kruskal-Wallis's and Dunn's tests.

RESULTS

Group III attained the best results for RSMI and BEAI. Moreover, it was the only group showing fibrin clot formation.

CONCLUSION

Citric acid was the most efficient conditioner for smear layer removal, collagen fiber exposure and blood cell adhesion. Moreover, it was the only group showing fibrin clot formation after PRP application.

CLINICAL SIGNIFICANCE

This study demonstrated that root conditioning followed by PRP application may favor blood cell adhesion on root surface which may optimize periodontal healing.

Evaluation of the Anticoagulants EDTA and Citrate, Theophylline, Adenosine, and Dipyridamole (CTAD) for Assessing Platelet Activation on the ADVIA 120 Hematology System

Background: Monitoring of platelet activation by the ADVIA® 120 Hematology System requires an anticoagulant and protocol that ensures that platelets are sphered and their activation status is not altered artifactually in vitro.

Methods: Blood from healthy controls was collected into tripotassium EDTA; citrate, theophylline, adenosine, and dipyridamole (CTAD); or a combination of both (E/C) and stored at ambient temperature or at 4 °C (E/C only) and then analyzed between 0 and 180 min later on the ADVIA 120. In addition, immunofluorescent flow cytometry was used to identify activated platelets and platelet-leukocyte aggregates.

Results: In blood stored with all three anticoagulants, the platelet count changed little, but the mean platelet volume (MPV) at first decreased and then increased, whereas the mean platelet component (MPC; an indicator of activation) changed in a reciprocal manner. The changes in MPV and MPC, which reflect platelet sphering and swelling, were greatest between 30 and 60 min in blood stored at ambient temperature, irrespective of which anticoagulant was used, and between 60 and 180 min when blood anticoagulated with E/C was stored at 4 °C. In all anticoagulants, the percentages of platelets expressing CD62P and of leukocytes in platelet-leukocyte aggregates increased significantly (P <0.01) over 180 min at ambient temperature. Only minimal (<2%) increases occurred when blood with E/C was stored at 4 °C.

Conclusions: When determining platelet activation ex vivo on the ADVIA 120, blood should be collected into E/C, stored at 4 °C, and analyzed between 60 and 180 min later; these conditions ensure maximum platelet sphering without concurrent artifactual platelet activation.

Influence of splenectomy on platelet morphometry and function

Functional and morphometric platelet abnormalities may be influenced by splenectomy and thus contribute to postoperative thrombohaemorrhagic complications, especially in patients with splenomegaly and/or platelet defects. We investigated platelet function, platelet secretion, and platelet morphometry before and one week after splenectomy in seven patients with normal platelet production and normal spleen size (Hodgkin's disease) and five patients with splenomegaly and platelet abnormalities (4 with myeloproliferative disorders and 1 with chronic myelomonocytic leukemia). Severe postoperative thrombohaemorrhagic complications occurred only in patients with myeloproliferative disorders, although platelet count and mean platelet volume increased in almost all patients after splenectomy. Four patients with myeloproliferative disorders had impaired platelet aggregation before splenectomy that improved in only one patient after surgery. Platelet buoyant density in this patient group was decreased before splenectomy and normalised thereafter. Concomitantly, intraplatelet concentrations of alpha-granular proteins increased. Before splenectomy, there was a positive correlation between platelet density and platelet volume in patients with Hodgkin's disease (r = 0.59, p less than 0.001), but not in patients with myeloproliferative disorders. There was no correlation between platelet density and platelet volume after splenectomy in either patient group. In conclusion, morphometric platelet abnormalities were found in all patients after splenectomy. In patients with myeloproliferative/myelodysplastic disorders, decreased platelet buoyant density normalised and intraplatelet concentrations of alpha-granule proteins were elevated after splenectomy. However, platelet function defects in this patient group were not corrected and may have been a major cause of thrombohaemorrhagic complications in the postoperative period.