Pneumonia is an inflammation of the lung tissue due to an infectious agent. Community acquired pneumonia (CAP) refers to pneumonia acquired outside of hospital or extended care facilities. CAP have an incidence of about 20% to 30% in developing countries ascompared to 3% to 4 % in developed countries[1]. The incidence varies markedly with age, being much higher in the extremes of age [2].

The causative agent in CAP is often difficult to establish. Even after extensive investigations; aetio-logical confirmation was achieved in not morethan 45% to70% of patients [3]. Streptococcus pneumoniae is the most commonly isolated pathogen responsible for 35% of patients. It is followed by Klebsiella pneumonia (22%), staphylococcus aureus (17%), mycoplasma (15%), Escherichia Coli (11%), beta hemolytic streptococci (7.5%) and other gram negative bacteria (9%) [4]. The morbidity and mortality levels vary significantly with the severity of the disease. CAP is one of the commonlife threatening infections, which results in deaths mostly in the developing countries [5]. The mortality in a study of CAP reported by Bansal et al [4] in India is 11 percent. The symptoms of CAP can range from mild to severe. The commons symptoms arefever (95.1%) followed by cough (75.7%) and breathlessness (65%) [6].

The knowledge of relevant prognostic factors might be useful for early identification of patients at high risk who requires intensive treatment. Prognostic scoring systems, such as pneumonia severity index (PSI) and the CURB-65 rule for CAP have been developed to address these issues. The most widely studied predictive model in CAP is the PSI score developed in USA. It is based on 20 variables that are used to derive a score which enables patient to be stratified in to five, risk categories [figure 2] The major limitation of PSI is the complexity involved in the calculation of the score. The CURB-65 score is based on the clinical information available at initial hospital assessment [figure 1]. This enables patients to be stratified according to increasing risk of mortality. However, the major deficiency of the CURB-65 approach is that it does not generally account for comorbid illness. Even though most of the burden in terms of mortality and morbidity occurs in under developed countries, not enough studies are availableto study the factors associated with an adverse prognosis of CAP in this region.

Those with CURB-65 scores 0 and 1 were grouped mild, 2 as moderate and scores 3,4 and 5 as severe. CAP patients with PSI risk class I, II, III were grouped as mild, PSI risk class IVas moderate and risk class V as severe.

Statistical analysis: Data was coded and entered in Microsoft Excel and statistical analysis was performed using Epiinfo software and SPSS (version10.0).Descriptive statistics of sociodemographic and clinical variables included frequencies, percentages, means and standard deviations. Receiver operating characteristic curves were calculated to evaluate how well the scores discriminated between patients who survived CAP and those who died, values for other parameters like need for ICU care and mechanical ventilation were also determined. The area under the curve (AUC) and 95% confidence intervals were obtained. A two-tailed p-value <0.05 was considered statistically significant.

Ethical Considerations: Clearance from the institutional ethical committee was obtained prior to the study. All the study participants weregiven subject information sheet along with a verbal briefing about the study and those who gave their written consent were only included in the study. At most care was taken to see that no personal identifiers in any form pertaining to the study participants were disclosed at any stage of this study

Scoring systems used

CURB-65 SCORE

PSI SCORE

The scores 0 and 1 were included in mild group, score 2 in moderate group, scores 3, 4,5 in severe group. Out of 68 patients, 37 were in mild group, 18 in moderate group and 23 in severe group.

Various prognostic parameters like need for ICU admission, need for mechanical ventilation and inhospital mortality were noted separately for mild, moderate and severe groups of CURB-65 and depicted in table 2.

Table-3: Showing the patient distribution for mild, moderate and severe groups of PSI

ICU ADM-ICU admission

Maximum mortality rates were noted in the severe group.

The subjects were given PSI scoring and were grouped into mild, moderate and severe. Out of 68 patients, 55 were in mild group, 18 in moderate group and 5 in severe group.

Various prognostic parameters like need for ICU admission, need for mechanical ventilation and inhospital mortality were noted separately for mild, moderate and severe groups of PSI score and depicted in table 3.

Figure-3: ROC curve for PSI and CURB-65 with inpatient mortality as outcome

The Area under the Curve (AUC) was more for CURB-65(0.935) as compared to PSI (0.920) when in-patient mortality is considered.

The CURB-65 has a better discriminatory power than PSI as far as the in-patient mortality is considered.

This is particularly important in developing countries like India where there is scarcity of resources both human and economic. It has effects onboth the level of treatment received by the patient as well as the overall expense related totreatment [7]. The first landmark study to prognosticate patients of CAP was conducted by the Research Committee of the BTS. Then formulated rules were transformed into a risk scoreby Lim and co-workers in 2002 at the university of Nottingham [8].

The scoring system consists of a six-point score determined at the time of initial presentation. In the original study, mortality risk in the six separate groups was as follows: group 0, 0.7%; group 1, 3.2%; group 2, 3%; group 3, 17%; group 4, 42%; and group 5, 57 percent. In 1997, Fine et al [9] introduced the pneumonia severity index (PSI), a product of the Pneumonia PORT study of ambulatory and hospitalized patients with CAP.

The rule stratifies patients into five classes of risk for death within 30 days of presentation. The lowest risk class (risk class I) comprises patients who are younger than 50 years of age, have none of the five important coexisting illnesses and have normal mental status and normal or only mildly abnormal vital signs at presentation.

Assignment to the remaining risk classes depends on the presence or absence of a set of medical history, physical examination, and laboratory findings [table 2]. Mortality rates in risk classes I, II, and III were low (0.1% to 0.4% in class I and 0.9% to 2.8% in class III), with correspondingly higher mortality rates in risk classes IV and V. The cumulative mortality rate of patients in risk classes I to III is less than one percent.

The variables in PORT study were derived from and validated in more than 50,000 patients, the largest database ever studied in the history of CAP research. A major limitation of the PSI is the unbalanced impact of age on the score, resulting in a potential under-estimation of severe pneumonia, particularly in younger otherwise healthy individuals [10].

Capelastegui et al [11] presented a comparative validation of the CURB-65, CRB-65 (which omits the blood urea measurement) and PSI scores in a population of 1,776 patients including 676 outpatients. The 30-day mortality increased with increasing score, and predictions of 30-day mortality were equivalent for all scores as assessed by ROC analysis.

Thus, both tools offer a valuable assessment of patient illness, but from different perspectives, and each is best at identifying patients at opposite ends of the disease severity.

Reviewing the literature, many studies are available which compares the discriminatory power of different everity assessment scores. Study by Aujesky et al showed PSI has got a higher discriminatory power for predicting mortality compared to CURB 65 score[12]. Busing et al study showed PSI and CURB 65 scores are equally powerful as prediction tools for mortality and need for mechanical ventilation [15]. Little information is available from India regarding prognostic factors in patients with community acquired pneumonia (CAP).

Shah BA et al showed both PSI and CURB-65 were found to have equal sensitivity to predict death from CAP. Specificity of CURB-65 was higher than that of PSI. However, PSI was more sensitive in predicting ICU admission than CURB-65. Study done by Khan et al concluded PSI as a good predictor of mortality, need of ICU admission and mechanical ventilation [18].

In our study both the scoring systems accurately classify CAP patients into different management groups based on in-patient mortality, need for ICU admission and mechanical ventilation with statistical significance. The CURB 65 has got the maximum AUC and hence better discriminatory power than the PSI score in all the three parameters. There are a few limitations of this study. The sample size in our study was small. Our study was conducted in a single tertiary care centre and hence the sample population might not represent the general population.

CAP patients in the mildgroup ofCURB 65 and PSI are at very low risk of mortality and lowest rates of ICU admission and mechanical ventilation, thus may be suitable for outpatient management. Patients in the moderate groups who are at intermediate risk of mortality should be considered for inpatient management. Patients in the severe groups who are at high risk of mortality and maximum rates of ICU admission and mechanical ventilation should be managed as having severe pneumonia in high dependency units.