Background To investigate whether routine biomarkers and blood leucocytes count could assist diagnosis of COVID-19-associated pneumonia in adult patients visiting the emergency department (ED).
Methods This monocentre retrospective study enrolled 254 patients with nasopharyngeal RT-PCR for SARS-COV-2, routine biomarkers (D-dimers, fibrinogen, C-reactive protein, procalcitonin, NTpro-BNP, cTnT-hs) and blood cell counts. Sensitivity and specificity were evaluated. An adjudication committee classified diagnostic probability as certain, probable, unlikely, and excluded, based on all available data, then distributed in 2 categories: high (certain and probable) and low probability (unlikely and excluded).
Results Between 25 th of February and 15 th of April, 2020, 254 of 388 patients could be analyzed. The adjudication committee classified 46 patients as definite, 18 as probable, 64 as unlikely, and 126 as excluded, corresponding to 64 high and 190 low probability. High and low probability patients differed for fibrinogen (P<0.0005) and white blood cell counts, notably leucocytes (P=0.0015), neutrophilic (P=0.0036), lymphocytes (P=0.0057), eosinophilic (P=0.027), and basophilic (P<0.001) counts. In a multivariate analysis, basophilic count < 25/µL (OR 3.048 [95%CI; 1.34-6.919]), neutrophilic count < 4000 /µL (OR 5.525 [95%CI; 2.20-13.855], and fibrinogen > 3g/L (OR 6355 [95%CI; 2.01-20.079] were independently associated with the diagnosis. Negative predictive values were 0.98 and 0.93 combining fibrinogen ( < 3g/L) and eosinophilic count ( < 80/µL), and fibrinogen and basophilic count ( < 25/µL), respectively.
Conclusion Changes in fibrinogen and white blood cells, notably basophilic count, showed interesting performance for the diagnosis COVID-19 associated pneumonia. Combining fibrinogen with either eosinophilic or basophilic count was helpful to exclude the diagnosis.