Clinical rule stratifies CAP patients’ cardiac risk

Researchers have generated and validated a clinical rule that accurately stratifies patients hospitalized for community acquired pneumonia (CAP) according to their risk for cardiac complications.

The team, led by Vicente Corrales-Medina (University of Ottawa, Ontario, Canada), say that the rule could help identify high-risk patients upon admission and help to reduce the contribution of such complications to treatment failure and mortality in CAP patients.

“This tool relies on variables that are easily obtainable at the time of pneumonia diagnosis and should prove useful for timely risk stratification in research and clinical settings,” they comment in the Mayo Clinic Proceedings.

The researchers used data on 1343 patients admitted for CAP of whom 27% experienced cardiac complications and 8% died from any cause within 30 days.

Using a logistic regression model and a backward elimination procedure, they identified several factors that remained in the final model: age, three preexisting conditions (heart failure, coronary artery disease, cardiac arrhythmia), two vital signs (pulse rate and blood pressure), and seven laboratory or radiographic parameters (hematocrit, white blood cell count, platelet count, serum urea nitrogen, serum glucose, arterial blood pH, and the presence of bilateral infiltrates on chest X-ray).

By assigning a point-scoring system to each parameter, the researchers generated four risk classes with the observed rates of cardiac complications ranging from 3% in class I to 72% in class IV.

They then tested the system in a validation cohort of 608 patients, in which predicted and observed cardiac complication rates both increased linearly: class I (5.5 vs 5.0%), class II (16.6 vs 8.2%), class III (38.7 vs 28.3%), and class IV (69.3 vs 48.9%).

Compared with the Pneumonia Severity Index, which has been proposed as a predictor for cardiac risk, the novel score was significantly more accurate with an area under the receiver operating characteristic curve of 0.78 versus 0.74. The novel score correctly reclassified the risk upward in 19% of patients who had a cardiac complication and reclassified down the risk of 25% of patients who did not.

“If further validated, the potential applications of our rule are various,” write Corrales-Medina et al. “Adequate risk stratification would allow researchers to most efficiently design and execute mechanistic and interventional studies in this area.”

They add: “In the clinical arena, identification of patients with CAP who are at high risk for cardiac complications could assist clinicians in their decision making regarding the disposition of patients admitted to the hospital for CAP and their discussions with these patients about their short-term prognosis.”

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