Neutrophil-to-lymphocyte ratio as an independent predictor of severe pertussis in children: A 17-year retrospective cohort study.

BACKGROUND

Despite the widespread implementation of vaccination programs, pertussis continues to spread and remains a major health threat to infants. The present study aimed to identify risk factors of severe pertussis in children to inform clinical decision-making and the development of prevention strategies.

METHODS

This retrospective cohort study included data from paediatric patients diagnosed with pertussis at Beijing You'an Hospital, Capital Medical University (Beijing, China), between January 2006 and December 2023. Multivariable logistic regression was performed to identify independent predictors of severe pertussis, and receiver operating characteristic (ROC) analysis was used to assess discriminative performance.

RESULTS

Data from 219 children with pertussis were divided in 2 groups according to predefined clinical criteria: severe (n = 21) and non-severe (n = 198). Compared with non-severe cases, severe cases experienced longer hospital stays (median 12 versus [vs.] 8 days) and higher rates of fever, cyanosis, sputum production, and respiratory distress. Marked inflammatory differences were observed, as follows: higher neutrophil counts (median 6.83 vs. 3.65 ×10⁹/L); elevated C-reactive protein (median 3.50 vs. 1.00 mg/L); procalcitonin (median 0.12 vs. 0.04 ng/mL); increased neutrophil-to-lymphocyte ratio (NLR; median 0.61 vs. 0.29); and a lower lymphocyte percentage (median 56.9 % vs. 69.5 %) (all p < 0.05). Multivariable analysis identified elevated NLR as an independent predictor of severe pertussis (adjusted odds ratio [OR] 1.884; 95 % confidence interval [CI] 1.157-3.066; P = 0.011). ROC curve analysis yielded an area under the curve (AUC) of 0.745 (95 % CI 0.640-0.850), with an optimal NLR cut-off of 0.475, yielding a sensitivity of 66.7 % and a specificity of 75.5 %.

CONCLUSION

Elevated NLR was an independent predictor of severe pertussis in children. Future multicentre prospective studies with standardised follow-up periods are warranted to validate these findings.