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.