Mortality and severity evaluation by routine pneumonia prediction models among Japanese patients with 2009 pandemic influenza A (H1N1) pneumonia

Abstract

Background: Influenza-related pneumonia, referred to as influenza pneumonia, was reported relatively more frequently during a recent influenza pandemic in 2009. The validity of adapting routine pneumonia severity prediction models for various types of pneumonia is unclear.

Methods: We conducted a nationwide survey to evaluate influenza pneumonia among adult patients in Japan. Questionnaires were sent to physicians working in departments of respiratory medicine at 2491 hospitals. Both the outcome and pneumonia severity, using invasive positive pressure ventilation (IPPV) as an indicator, were evaluated by routine pneumonia severity index (PSI), CURB-65 (confusion, urea, respiratory rate, blood pressure, and age ≥ 65 years), and A-DROP (age, dehydration, respiration, disorientation, and blood pressure).

Results: Data collected from 320 patients with influenza pneumonia, including 25 cases (7.8%) of death and 43 (13.4%) of IPPV, were analyzed. Although all routine prediction models showed that higher mortality tended to be associated with a higher risk class/grade, the actual mortality rates were higher than predicted. The risk class of mortality calculated by the PSI was influenced by pneumonia patterns. Although pneumonia severity was similarly predicted, the types of pneumonia also affected severity in all prediction models. A-DROP showed the highest accuracy on receiver operating characteristic analysis for both mortality and severity.

Conclusions: CURB-65 and A-DROP are fair predictors of mortality regardless of pneumonia patterns. However, the current pneumonia prediction models may underestimate the severity and appropriate site of care for patients with influenza pneumonia.

Keywords: A-DROP; CURB-65; Influenza; Influenza pneumonia; Pneumonia severity index.