Tese
Avaliação da fração de plaquetas imaturas no diagnóstico da trombocitopenia imune e sua relação com a gravidade da Covid-19
Fecha
2022-11-25Autor
Pereira, Karla Nunes
Institución
Resumen
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.