Assessment of platelet/lymphocyte ratio as an acute phasereactant in patients applied with suspect of COVİD-19 andcomparison with CRP, D-dimer

Aim: Although RT-PCR is the gold standard method used for diagnosis since the first days of the COVID-19 pandemic, which has affected the whole world and our country since December 2019, the test results cannot be obtained in a short time, and it takes at least 24 hours to repeat the test. We planned to determine the laboratory parameters that can help clinicians in emergency department triage in predicting diagnosis and prognosis. Materials and Methods: In our retrospective, cross-sectional, hospital-based and single-center study, 833 patients over 18 years of age who presented to the Adult Emergency Service of the Baskent University Hospital in Ankara between March 11, 2020 and August 31, 2020 have been evaluated as a case with suspected COVID-19 at the time of admission. Demographic data of all patients, vital signs and complaints at the time of admission, results of laboratory tests and RT-PCR swab samples, computed tomography results, need for service-intensive care hospitalization, need for additional treatment modalities, morbidity and mortality information in the prepared data forms have been recorded. IBM SPSS Statistics 20 program for statistical evaluations has been used. Results: 51,1% of the patients included in the study were female and 48,9% were male. The patients included in the study under 3 different groups have been examined. Based on the PCR results, patients have been divided into two groups: COVID-19 and non-COVID. PCR-positive patients have been divided into two groups according to survival and infiltration findings on CT. While the mean age of the COVID group was 47,87 ± 18,80 years, the mean age of the non-COVID group was 51,28 ± 22,47 years. When the three parameters we focused on among the laboratory values examined for each subgroup have been examined, the only parameter that showed a significant difference between the COVID and non-COVID groups was D-dimer (p=0,001). The mean D-dimer (0,79±1,75 mg/L) in individuals with COVID was significantly lower. CRP (p<0,001, p<0,001, respectively) and D-dimer (p<0,001, p=0,016, respectively) showed significant differences in subgroups of PCR-positive patients with/without survival and/or with/without infiltration on CT. While the mean of D-dimer was 3,27±5,09 mg/L in the non-survival group, the mean of the group with infiltration on CT has been recorded as 0,99±2,21 mg/L. While the mean of CRP in the non-survival group was 128,13±98,39 mg/L, the mean of the group with infiltration on CT has been recorded as 44,45±63,17 mg/L. Our analyzes for PLR were not significant for any subgroup. In ROC analyzes for the three biomarkers (PLR, D-dimer, CRP) we focused on, no meaningful data have been obtained for PLR, while cut-offs for CRP and D-dimer have been defıned. We concluded that PCR positivity increased in patients with D-dimer value below 0,94 mg/L. We determined that mortality increased in patients with D-dimer value above 0,61 mg/L or CRP value above 12,6 mg/L. The ROC analysis we performed to determine threshold values in treatment modalities is among the rare studies in the literature. Conclusion: Knowledge of the defining features of the disease and the factors that influence its prognosis is important in the fight against COVID-19. We believe that evaluation with clinical, CT findings and laboratory results will guide clinicians more accurately in terms of pre-diagnosis and prognosis, rather than using laboratory results alone in the triage of patients who apply to the emergency department with the suspicion of COVID.