COVID-19 etiology can be accurately identified from abnormalities in white blood cell morphology based on a few cell population data values and the neutrophil/lymphocyte ratio (NLR). The predictive ability was not improved with the current systemic inflammation biomarkers used. These are among the study findings published in Archivos de Bronconeumología.
Researchers sought to evaluate the utility of detecting COVID-19 in patients admitted for community-acquired pneumonia (CAP) of varying etiologies using differential white cell count and cell population data (CPD).
The investigators conducted a multicenter prospective observational cohort study (ClinicalTrials.gov Identifier: NCT04930926) that included 1782 adult patients diagnosed with CAP who were admitted to 3 national public health service network teaching hospitals in northern Spain from November 2019 to November 2021. Some of the exclusions included being discharged within the previous 14 days from palliative care or an acute care hospital, or being HIV positive or chronically immunosuppressed. Detailed information concerning the activation status and functional activity of white cells was obtained at baseline with a Sysmex XN-20 analyzer.
The validation set included 717 patients; of those, more than 70% were COVID-19-positive. The derivation cohort (n=1065) had 791 patients with confirmed COVID-19 (mean [SD] age, 62.13 [14.37] years; 35% female) and 274 patients without COVID-19 (mean [SD] age. 65.42 [16.62] years; 39% female) (P <.001). In comparing patients with and without COVID-19 within the derivation cohort, investigators found that deaths within 30 days were 54 vs 12, respectively; invasive mechanical ventilation was required by 74 vs 10 patients, respectively; admission to the intensive care unit occurred with 139 vs 20 patients, respectively; and noninvasive mechanical ventilation was required by 238 vs 35 patients, respectively.
The investigators developed a weighted multivariate prediction model for identifying positive COVID-19 status based on their findings that all CPD parameters had significant differences between those with and without COVID-19 with the exception of monocytes fluorescence intensity (MO-Y). The multivariate prediction model showed that lower values for neutrophils (NE-X, NE-WY), lymphocytes (LY-Z, LY-WY), and monocytes (MO-WX, MO-WY, and MO-Z) and a lower neutrophil-to-lymphocyte ratio were related to COVID-19 etiology. The model had good discrimination and calibration (area under the curve 0.819 [0.790-0.846]) Comparing this model to another model that included biomarkers showed no significant differences (P =.18).
Significant study limitations include the need for a Sysmex XN analyzer to perform analysis and the lack of children analyzed in the current study.
This study “highlights the utility of commonly used white blood cell analysis to distinguish between pneumonia due to COVID-19 from pneumonia of other etiologies,” the researchers concluded, noting that white blood cell measures were found to accurately identify COVID-19 throughout different pandemic waves. “Our data suggest that the straightforward evaluation of neutrophil activation can identify COVID-19 in patients with CAP in a way that is both easy and inexpensive,” said study authors.
Uranga A, Urrechaga E, Aguirre U, et al.; LEUCOCAP Study Group. Utility of differential white cell count and cell population data for ruling out COVID-19 infection in patients with community-acquired pneumonia. Arch Bronconeumol. Published online September 21, 2022. doi:10.1016/j.arbres.2022.08.011