Method
Ethics committee approval for this single-center, retrospective, and observational study was obtained from the local committee.
This study was carried out in a tertiary university hospital. Patients who were admitted to the emergency department, suspected of having COVID-19, and hospitalized and whose PCR test was positive were included in the study from March to October 2020. Regardless of the number of tests submitted, any PCR result that appeared positive at least once was considered positive, while other results were considered negative. Patients who were discharged against medical advice and referred to other hospitals were excluded from the study. Patients, who were discharged against medical advice, transferred to other hospitals and had no results of at least one of the d-dimer, fibrinogen and albumin parameters were excluded.
The following pieces of patient data were recorded from the patients’ e-files using the Hospital Information Management Systems program: d-dimer level; fibrinogen level; albumin level; his/her complaint (fever, cough, shortness of breath); vital signs; comorbidities; information about their ward/ICU admission; hospital outcome (discharge, exitus in-hospital); and in-hospital mortality status. The DAR was obtained by dividing the d-dimer level by the albumin level. The FAR was obtained by dividing the fibrinogen level by the albumin level. The primary outcomes of the study were the prediction of in-hospital mortality using the DAR and the FAR and the determination of whether the DAR and FAR was a more accurate predictor than the d-dimer, fibrinogen and albumin levels.
Statistical analysis of the data was performed using the SPSS 20.0 (SPSS Inc., Chicago, IL) package program. Histograms and the Kolmogorov-Smirnov test was used for the test of normality of the data. According to the normality analysis result, all quantitative data were expressed as median (25% -75% quarters) since they did not show a normal distribution, while categorical variables were expressed as frequency (percentage). The differences between the groups were investigated using the Mann–Whitney U test. Intragroup comparisons of the categorical variables were made using the chi square test and the Fisher’s exact test. Receiver operating characteristic (ROC) analysis was performed to determine the in-hospital mortality predictive power of the d-dimer, fibrinogen, albumin, DAR, and FAR levels. The optimum cut-off levels of the biochemical parameters were determined using Youden’s index (sensitivity + 1−specificity). The sensitivity, specificity, and positive and negative predictive values of the parameters were calculated for the optimum cut-off levels. The odds ratios of the groups categorized by the optimum cut-off values of d-dimer, fibrinogen, albumin, DAR, and FAR in predicting in-hospital COVID-19 mortality were calculated using univariate logistic regression analysis. The area under the curve (AUC) and odds ratio values were used to compare the mortality predictive power of parameters. Statistical significance was set at p<0.05.