Background: Neutrophil to lymphocyte ratio (NLR) on admission was reported to be a
predictor of pneumonia after stroke. The aim of this study was to investigate the association between
the temporal change of NLR and post-stroke infection and whether infection modified the
effect of NLR on the outcome.
Methods: We enrolled patients with acute ischemic stroke within 24 h after onset. The blood was
collected on admission, day 1, 3, 7 after admission to detect white blood cells (WBC), neutrophils,
and lymphocytes. Primary outcomes included pneumonia, urinary tract infection (UTI), other infection,
and the secondary outcome was 3-month death.
Results: Of 798 stroke patients, 299 (37.66%) developed infection with 240 (30.23%) pneumonia,
78 (9.82%) UTI, and 9 (1.13%) other infection. The median time of infection occurrence was 48 h
(interquartile range 27-74 h) after onset. NLR reached to the peak at 36 h. For all outcomes, NLR
at 36 h after stroke had the highest predictive value than WBC, neutrophil, lymphocyte. NLR was
independently associated with the presence of any infection (odds ratio [OR] 1.11, 95% confidence
interval [CI] 1.05-1.17), pneumonia (OR 1.12, 95%CI 1.05-1.19), but not UTI (OR 0.95, 95%CI
0.89-1.01). Adding infection or the interaction term did not substantially change the OR of NLR
predicting 3-month death (OR 1.09, 95%CI 1.01, 1.17).
Conclusion: Increased NLR around 36 h after stroke was a predictor of infection in patients with
acute ischemic stroke. The increased NLR value was associated with a higher risk of 3-month
death, which was independent of poststroke infection.