Elevated platelet-to-lymphocyte ratio (PLR) is independently associated with stroke-associated pneumonia in acute ischemic stroke patients, exhibiting a non-linear threshold-dependent relationship, though its standalone discriminatory performance is modest.
SAP occurred in 20.6% of the study cohort of AIS patients.
PLR was significantly higher in AIS patients who developed SAP compared to those who did not.
Log2-transformed PLR remained independently associated with SAP in the fully adjusted multivariable logistic regression model.
The association between PLR and SAP followed a non-linear, threshold-dependent pattern with an inflection point at PLR = 224.8.
PLR alone had modest discriminatory performance for SAP, with an AUC of 0.584, substantially lower than CRP and the A2DS2 score.
Subgroup analyses were performed across seven clinical variables to assess consistency of the PLR-SAP association.
This research suggests that a simple blood test ratio — the platelet-to-lymphocyte ratio (PLR), derived from a standard complete blood count — is associated with the development of pneumonia following a stroke, known as stroke-associated pneumonia (SAP). Among 1,745 patients hospitalized with acute ischemic stroke, about 1 in 5 developed SAP, and those who did had notably higher PLR values. Even after accounting for other medical factors, higher PLR remained linked to greater odds of developing SAP, particularly when PLR exceeded a threshold of approximately 224.8, above which the risk more than doubled. However, PLR on its own is not a highly accurate predictor of SAP — its ability to distinguish who will and will not develop pneumonia (AUC of 0.584) was considerably weaker than established tools like C-reactive protein (AUC 0.825) or the A2DS2 clinical score (AUC 0.757). When PLR was combined with these other measures, predictive performance improved slightly. The relationship between PLR and SAP was also non-linear, meaning risk did not increase steadily with every rise in PLR but rather jumped meaningfully only above a certain level. This research suggests that PLR, because it is already calculated from routine blood tests at no extra cost, could serve as an accessible early warning signal to help clinicians identify stroke patients at higher risk of developing pneumonia. The authors call for larger, prospective studies across multiple hospitals to confirm these findings before PLR could be formally incorporated into clinical risk assessment tools.
Duan T, Xu C, Zhan J, Wang L, Wu Z, Xu Y, et al.. (2026). Elevated platelet-to-lymphocyte ratio is associated with stroke-associated pneumonia in acute ischemic stroke: a retrospective cohort study.. Frontiers in neurology. https://doi.org/10.3389/fneur.2026.1891885