Comparison of the prognostic performance of the CURB-65 and a modified version of the pneumonia severity index designed to identify high-risk patients using the International Community-Acquired Pneumonia Collaboration Cohort.

BACKGROUND: Although the PSI and CURB-65 represent well-validated prediction rules for pneumonia prognosis, PSI was designed to identify patients at low risk and CURB- 65 patients at high risk of mortality. We compared the prognostic performance of a modified version of the PSI designed to identify high-risk patients (i.e., PSI-HR) to CURB-65 in predicting short-term mortality. METHODS: Using data from 6 pneumonia cohorts, we designed PSI-HR as a 6-class prediction rule using the original prognostic weights of all PSI variables and modifying the risk score thresholds to define risk classes. We calculated the proportion of low-risk and high-risk patients using CURB-65 and PSI-HR and 30-day mortality in these subgroups. We compared the rules' sensitivity, specificity, positive and negative predictive values for mortality at all risk class thresholds and assessed discriminatory power using areas under their receiver operating characteristic curves (AUROCs). RESULTS: Among 13,874 patients with pneumonia, 1,036 (7.5%) died. For PSI-HR versus CURB-65, aggregate mortality was lower in low-risk patients (1.6% vs. 2.2%, p = 0.005) and higher in high-risk patients (36.5% vs. 32.2%, p = 0.27). PSI-HR had higher sensitivities than CURB-65 at all thresholds; PSI-HR also had higher specificities at the 3 lowest thresholds and specificities within 0.5% points of CURB-65 at the 2 highest thresholds. The AUROC was larger for PSI-HR than CURB- 65 (0.82 vs. 0.77, p < 0.0001). CONCLUSIONS: PSI-HR demonstrated superior prognostic accuracy to CURB-65 at the lower end of the severity spectrum and identified high-risk patients with nonsignificant higher short-term mortality at the higher end.

Role of 'atypical pathogens' among adult hospitalized patients with community-acquired pneumonia.

BACKGROUND AND OBJECTIVE: Agents such as Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophila are recognized as important causes of community-acquired pneumonia (CAP) worldwide. This study examined the role of these 'atypical pathogens' (AP) among adult hospitalized patients with CAP. METHODS: A prospective, observational study of consecutive adult CAP (clinico-radiological diagnosis) patients hospitalized during 2004-2005 was conducted. Causal organisms were determined using cultures, antigen testing and paired serology. Clinical/laboratory/radiological variables and outcomes were compared between different aetiologies, and a clinical prediction rule for AP was constructed. RESULTS: There were 1193 patients studied (mean age 70.8 +/- 18.0 years, men 59.3%). Causal organisms were identified in 468 (39.2%) patients: 'bacterial' (48.7%), 'viral' (26.9%), 'AP' (28.6%). The AP infections comprised Mycoplasma or Chlamydophila pneumoniae (97.8%) and co-infection with bacteria/virus (30.6%). The majority of AP infections involved elderly patients (63.4%) with comorbidities (41.8%), and more than one-third of patients were classified as 'intermediate' or 'high' risk CAP on presentation (pneumonia severity index IV-V (35.1%); CURB-65 2-5 (42.5%)). Patients with AP infections had disease severities and outcomes similar to patients with CAP due to other organisms (oxygen therapy 29.1% vs 29.8%; non-invasive ventilation 3.7% vs 3.3%; admission to the intensive care unit 4.5% vs 2.7%; length of hospitalization 6 day vs 7 day; 30-day mortality: 2.2% vs 6.0%; overall P > 0.05). Age <65 years, female gender, fever > or =38.0 degrees C, respiratory rate <25/min, pulse rate <100/min, serum sodium >130 mmol/L, leucocyte count <11 x 10(9)/L and Hb < 11 g/dL were features associated with AP infection, but the derived prediction rule failed to reliably discriminate CAP caused by AP from bacterial CAP (area under the curve 0.75). CONCLUSIONS: M. pneumoniae and C. pneumoniae as single/co-pathogens are important causes of severe pneumonia among older adults. No reliable clinical indicators exist, so empirical antibiotic coverage for hospitalized CAP patients may need to be considered.