Risk Factors for Complicated Parapneumonic Effusion and Empyema on Presentation to Hospital with Community Acquired Pneumonia

James D Chalmers ^1*, Aran Singanayagam ¹, Caroline Scally ¹, Ali Fawzi ¹, Maeve P Murray ¹ and Adam T Hill ¹

¹ Royal Infirmary of Edinburgh, United Kingdom

^* To whom correspondence should be addressed. E-mail: jamesdchalmers{at}googlemail.com.

Accepted 10 December 2008

Abstract

Backgound: The aim of this study was to identify key factors on admission predicting the development of complicated parapneumonic effusion or empyema in patients admitted with community acquired pneumonia.

Methods: We conducted a prospective observational study of patients admitted with community acquired pneumonia in NHS Lothian, UK. We used multivariate regression analyse to evaluate factors that could predict the development of complicated parapneumonic effusion or empyema including admission demographics, clinical features, laboratory tests, pneumonia specific (PSI, CURB65 and CRB65) and generic sepsis scoring systems (APACHE II, SEWS, SIRS).

Results: 1269 patients were included in the study and 92 patients (7.2%) developed complicated parapneumonic effusion or empyema. The pneumonia specific and generic sepsis scoring systems had no value in predicting complicated parapneumonic effusion or empyema.

Multivariate logistic regression identified albumin <30g/L adjusted odds ratio (AOR) 4.55 (95% confidence interval 2.45-8.45,p<0.0001), sodium <130mmol/l AOR 2.70 (1.55-4.70,p=0.0005), platelet count >400x109/L AOR 4.09 (2.21-7.54,p<0.0001), C-reactive protein >100mg/l AOR 15.7 (3.69-66.9,p<0.0001) and a history of alcohol abuse AOR 4.28 (1.87-9.82,p=0.0006) or intravenous drug use AOR 2.82 (1.09-7.30,p=0.03) as independently associated with development of complicated parapneumonic effusion or empyema. A history of COPD was associated with decreased risk AOR 0.18 (0.06-0.53,p=0.002).

A 6 point scoring system using these combined variables had good discriminatory value AUC 0.84 (95% confidence interval 0.81-0.86,p<0.0001).

Conclusion: This study has identified 7 clinical factors predicting the development of complicated parapneumonic effusion or empyema. Independent validation is needed.