Evaluation of morphological parameters, PLR and NLR inflammation indicators in patients with long-term COVID-19 of mild and severe complexity

COVID-19 can have long-lasting effects, but the effects on blood parameters and inflammation are poorly understood. The aim of this study was to evaluate morphological and inflammatory markers in long-term COVID-19 patients.To evaluate complete blood count, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and morphology in mild versus severe long COVID-19.In total, 39 long COVID-19 patients were stratified into mild (n = 25) and severe (n = 14) groups. Blood counts, NLR, PLR were measured. Cell morphology was analysed. ROC curves were used to determine biomarker thresholds. Survival was assessed using Kaplan–Meier curves.Severe patients had lower leukocytes but higher neutrophils, indicating greater inflammation. NLR and PLR were significantly increased in severe patients compared to mild patients (NLR 12 vs 8; PLR 140 vs 100). NLR and PLR were higher than in controls, confirming their utility as inflammatory markers. NLR and PLR effectively discriminated between mild and severe disease. High NLR and PLR predicted poorer prognosis. Altered leukocyte morphology such as cytoplasmic vacuolization correlated with severity.NLR and PLR are promising biomarkers for assessing severity of long COVID-19, while morphological changes in blood cells provide additional evidence of inflammation. Further studies in larger populations are warranted.