Avaliação da fração de plaquetas imaturas no diagnóstico da trombocitopenia imune e sua relação com a gravidade da Covid-19

Abstract

Platelets are cytoplasmic fragments of megakaryocytes, cells present in the bone marrow, which are key players in hemostasis. Adequate platelet kinetics, with a balance between production, activation, and apoptosis, is essential to maintain the stability of this process. Hemostasis imbalance due to different causes results in changes in the number and/or function of platelets. In immune thrombocytopenia (ITP), this imbalance leads to a reduction in the number of platelets. In COVID-19, the imbalance results in platelet hyperactivation with consequent immunothrombotic dysregulation. Recently, in addition to counting the number of platelets, the analysis of other platelet parameters, including mean platelet volume (MPV), immature platelet fraction (IPF), absolute number of platelets, immature platelets (AIPC), platelet cell count (PCT), large platelet ratio (P-LCR), and PDW (platelet distribution amplitude) are performed using more advanced automated equipment. The aim of this study was to evaluate IPF (%), AIPC (× 109 /L), and MPV (fL) in ITP diagnosis and platelet changes present in the pathophysiology of COVID-19. EDTA-containing whole blood samples from patients diagnosed with ITP (41 patientes) and from patients diagnosed with COVID-19 (152 patients) were analyzed for the determination of these markers in the XE5000 analyzer. Samples from blood donors were used as the healthy control group. Results showed that a cutoff of 6.4% for IPF can be used as a laboratory marker for the diagnosis of ITP. In the case of COVID-19, results showed that patients requiring intensive care had a median of 6.20% (4.70–8.53) and 14.98x109 /L (11.15–21.25) for IPF and AIPC, respectively. For patients with COVID-19 without intensive treatment, the values obtained were 5.30% (3.20–6.80) and 13.39x109 /L (8.64–18.93). For the control group without COVID-19, the values were 3.40% (2.55–4.85) and 7.78x109 /L (5.58–9.97). The MPV values were 10.4 fL (9.90–11.10), 9.80 fL (9.30–10.40), and 10.1 fL (9.65–11.00) for the control group, patients with COVID-19 without intensive treatment, and those in need of intensive treatment, respectively. The results suggest that these markers can be used to assess the severity of COVID-19. Our results show that once platelet parameters are standardized with defined reference values, they can be useful in clinical practice for confirmatory diagnostic purposes in the case of ITP or for the assessment of the severity and follow-up of the disease in the case of COVID19.