en Infectious Diseases Infectious Diseases Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="color:#0000ff;"><strong><em>Background:</em></strong></span> The present study aimed to compare the complete blood count (CBC) indices between COVID-19 patients and the control group, and assess the relationship of these indices with COVID-19 prognosis given the role of complete blood counts in the COVID-19 prognosis.<br> <span style="color:#0000ff;"><strong><em>Methods:</em></strong></span> COVID-19 patients (confirmed by PCR or CT-Scan) who visited Imam Hospital in Sari were selected in this case-control study. The control group was selected from Tabari cohort population who were matched with the case group in terms of gender and age. CBC, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and outcome of the disease (in the case group) were assessed in this study.<br> <span style="color:#0000ff;"><strong><em>Results:</em></strong></span> The number of participants in the case and control groups was 527. Of these, 464 (44%) were females. Platelet count, lymphocyte count, and hemoglobin concentration were also higher in the control group (p = 0.000). NLR and PLR were significantly higher in COVID-19 patients compared to the control group (P = 0.000). NLR had a significant relationship with severity of the disease. NLR was two times higher in the patients who died of COVID-19 than those who recovered (P = 0.000). ROC curve analysis for diagnostic values of NLR and PLR showed that the areas under the ROC curves for NLR and PLR were 0.703 (95% CI: 0.64-0.76) and 0.535 (95% CI: 0.46-06) respectively.<br> <span style="color:#0000ff;"><strong><em>Conclusion:</em></strong></span> NLR can be used as a prognostic marker for COVID-19 given the significant difference of NLR between those died and recovered from COVID-19.</span></span> Neutrophil-to-Lymphocyte ratio, Platelet-to-Lymphocyte ratio, COVID-19, Prognosis 531 535 http://caspjim.com/browse.php?a_code=A-10-672-2&slc_lang=en&sid=1 Mohammad Eslamijouybari sina.s28@gmail.com 100319475328460026227 100319475328460026227 No Keyvan Heydari kvan3787@gmail.com 100319475328460026228 100319475328460026228 No  Iradj Maleki iradj2001@yahoo.com 100319475328460026229 100319475328460026229 No Mahmood Moosazadeh mmoosazadeh1351@gmail.com 100319475328460026230 100319475328460026230 No Akbar Hedayatizadeh-Omran akbar_hedayati@yahoo.com 100319475328460026231 100319475328460026231 No Lale Vahedi lalevahedi@gmail.com 100319475328460026232 100319475328460026232 No Roya Ghasemian roya31gh@yahoo.com 100319475328460026233 100319475328460026233 No Ali Sharifpour asharifpour_0209@yahoo.com 100319475328460026234 100319475328460026234 No Reza Alizadeh-Navaei reza_nava@yahoo.com 100319475328460026235 100319475328460026235 Yes Gastrointestinal Cancer Research Center, Non-Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran