NLR a stronger predictor of COVID-19 outcomes than RSV, influenza

The neutrophil-to-lymphocyte ratio (NLR) appears to have stronger prognostic value for the coronavirus disease 2019 (COVID-19) than for influenza and the respiratory syncytial virus (RSV), a recent study has found.

Researchers retrospectively assessed 722 COVID-19 (mean age 67±28 years, 57.6 percent men), 2,213 influenza (mean age 73±26 years, 48.3 percent men), and 482 RSV (mean age 79±18 years, 46.4 percent men) patients. The corresponding median NLR values were 4.5, 7.5, and 6.8, with influenza patients having significantly higher levels than both RSV and COVID-19 patients.

Age-stratified analysis further revealed that across all age groups, COVID-19 patients had significantly lower NLR than their influenza counterparts. In patients aged ≥50 years, NLR in the COVID-19 group was significantly lower than both the influenza and RSV groups.

Two-way analysis of variance was then performed to assess the association of log-transformed NLR with poor clinical outcome, defined as a composite of either the need for mechanical ventilation and death within 30 days of admission.

The researchers detected a significant main effect for virus type, such that COVID-19 patients presented with significantly lower NLR levels than RSV and influenza comparators (p<0.001). Moreover, simple main effects analysis confirmed that high NLR was correlated with poor outcome in COVID-19 patients, but not in the RSV and influenza groups.

Receiver operating characteristic curve analysis found that the optimal cutoff for NLR in COVID-19 was 6.82, such that scores above this threshold yielded a nearly threefold increase in the likelihood of poor clinical outcomes (odds ratio, 2.88; p<0.001).