A model for predicting bacteremia in patients with community-acquired pneumococcal pneumonia: a retrospective observational study

Abstract

Background: Pneumococcal pneumonia causes high morbidity and mortality among adults. This study aimed to identify risk factors for bacteremic pneumococcal pneumonia, and to construct a prediction model for the development of bacteremia in patients with community-acquired pneumococcal pneumonia.

Methods: We retrospectively analyzed data from patients hospitalized with community-acquired pneumococcal pneumonia between April 2007 and August 2015. Logistic regression models were applied to detect risk factors for pneumococcal bacteremia, and a receiver operating characteristic curve was used to devise a prediction model.

Results: Based on the results of sputum cultures, urine antigen tests, and/or blood cultures, 389 patients were diagnosed with pneumococcal pneumonia, 46 of whom had bacteremia. In the multivariate analysis, age < 65 years, serum albumin level < 3.0 g/dL, need for intensive respiratory or vasopressor support (IRVS), and C-reactive protein level > 20 mg/dL were identified as independent risk factors for the development of pneumococcal bacteremia. The bacteremia prediction score based on receiver operating characteristic curve analysis had a sensitivity of 0.74 and a specificity of 0.78 in patients with two risk factors. The area under the receiver operating characteristic curve was 0.77 (95% confidence interval (CI), 0.70-0.85).

Conclusions: Age < 65 years, hypoalbuminemia, IRVS, and high C-reactive protein level on admission are independent risk factors for the development of bacteremia in patients with community-acquired pneumococcal pneumonia. A prediction model based on these four risk factors could help to identify patients with community-acquired pneumococcal pneumonia at high risk of developing bacteremia; this can be used to guide antibiotic choices.

Trial registration: UMIN-CTR UMIN 000004353 . Registered 7 October 2010. Retrospectively registered.

Keywords: Bacteremia; Blood culture; Community-acquired pneumonia; Pneumococcal pneumonia.

Fig. 1

Receiver-operating characteristic curve for four factors predictive of bacteremia in community-acquired pneumococcal pneumonia patients. Area under the curve = 0.77 (95% confidence interval, 0.70–0.85). The four factors predictive of bacteremia were age < 65 years, albumin level ˂3.0 g/dL, need for intensive respiratory or vasopressor support, and C-reactive protein level > 20 mg/dL. Each factor was allocated one point in the prediction model. For patients scoring two points, the specificity was 0.78 and sensitivity was 0.74

Fig. 2

Proportion of patients with community-acquired pneumococcal pneumonia according to bacteremia prediction model score. Four significant risk factors for bacteremia in community-acquired pneumococcal pneumonia patients were identified (age < 65 years, albumin level < 3.0 g/dL, need for intensive respiratory or vasopressor support, and C-reactive protein level > 20 mg/dL). Each risk factor was allocated one point in the bacteremia prediction model. The figure shows the proportion of patients with 0, 1, 2, 3, and 4 risk factors with and without bacteremia