Development and internal validation of a prediction rule for post-stroke infection and post-stroke pneumonia in acute stroke patients

Abstract

Introduction: Patients with acute stroke are at high risk for infection. These infections are associated with unfavourable outcome after stroke. A prediction rule can identify the patients at the highest risk for strategies to prevent infection. We aim to develop a prediction rule for post-stroke pneumonia and other infections in patients with acute stroke.

Patients and methods: We used data from the Preventive Antibiotics in Stroke Study, a multicentre randomised trial comparing preventive ceftriaxone vs. standard stroke care in patients with acute stroke. Possible predictors for post-stroke pneumonia or infection were selected from the literature. Backward elimination logistic regression analysis was used to construct prediction rules for pneumonia or infection. Internal validation was performed and a risk chart was constructed. We adjusted for preventive antibiotic use.

Results: Pneumonia was diagnosed in 159 of the 2538 included patients, and infection in 348. Pneumonia was predicted by higher age, male sex, pre-stroke disability, medical history of chronic obstructive pulmonary disease, more severe stroke, dysphagia and intracerebral haemorrhage (rather than ischaemic stroke). Infections were predicted by higher age, male sex, history of diabetes, chronic obstructive pulmonary disease, more severe stroke, dysphagia, use of bladder catheter, preventive antibiotic use and intracerebral haemorrhage. With the prediction rule developed, risks for pneumonia ranged from 0.4% to 56.2% and from 1.8% to 88.0% for infection. Discrimination of the score was good (C-statistic, 0.84; 95% CI: 0.81-0.87 and 0.82; 95% CI: 0.79-0.84 for pneumonia and infection).

Conclusions: The Preventive Antibiotics in Stroke Study pneumonia and infection rule identify patients at the highest risk for post-stroke pneumonia or infection and may be used for future studies and novel therapies, after confirmation in an external population.

Keywords: Stroke; infection; pneumonia; prediction.

Figure 1.

Calibration plot for pneumonia and infection. Legend ideal: line drawn for the situation in which predicted probabilities perfectly match the observed probabilities. Nonparametric: line displaying observed probabilities. Grouped observations: observed probabilities for 10 groups of equal size.

Figure 2.

Score on PASS prediction rule and predicted risks for pneumonia and infection. PASS: preventive antibiotics in stroke study.