Prognostic factors for mortality in SG pneumonia patients vary across age groups
Different age groups of patients with community-acquired pneumonia (CAP) in Singapore exhibit distinct risk factors for mortality, according to a study.
Furthermore, pneumonia severity index (PSI) appears to achieve significantly better mortality prediction performance than CURB-65 (Confusion, Uraemia, Respiratory rate ≥ 30 per minute, low Blood pressure, age 65 years or older). However, the discriminative power of PSI decreases with advancing age, said researchers from the Singapore General Hospital.
Researchers looked at a cohort of 1,902 patients with CAP from three age groups and evaluated a total of 27 prognostic factors influencing mortality. Twenty of which were derived from the PSI scoring tool and included demographic factors, comorbidities, initial vital signs, laboratory test results and chest radiography findings.
The overall rate of 30-day mortality, the primary outcome, was 15.7 percent. Of the 299 deaths recorded, 85.3 percent were in-hospital deaths and 14.7 percent occurred after discharge. [Singapore Med J 2017;doi:10.11622/smedj.2017079]
An increase in individual mortality rates was noted with each successive age group, from 7.3 percent in the 18 to 64 years group (n=614) to 16.1 percent in the 65 to 84 years group (n=944) and to a further 29.7 percent in the ≥ 85 years group (n=344; p<0.001).
In a multivariate logistic regression model, mortality increased in the presence of malignancy (odds ratio [OR], 8.1; p<0.001) and tachycardia (pulse rate ≥125 per minute; OR, 4.3; p<0.001) among CAP patients aged 18 to 64 years.
Among patients aged 65 to 84 years, mortality was significantly associated with male gender (OR, 2.0; p=0.001), malignancy (OR, 2.8; p<0.001) and congestive heart failure (OR, 2.6; p=0.003). Eight other parameters reflecting acute disease severity emerged as prognostic indicators of mortality, with altered mental status (OR, 3.3; p=0.005), tachycardia (OR, 3.2; p<0.001) and arterial pH <7.35 (OR, 3.4; p<0.001) ranking as the top three factors.
For patients aged ≥85 years, significant predictors of mortality were altered mental status (OR, 6.1; p=0.001), tachycardia (OR, 2.5; p=0.043), blood urea nitrogen (OR, 2.0; p=0.019), hypoxaemia (OR, 2.7; p=0.009), arterial pH (OR, 3.0; p=0.03) and pleural effusion (OR, 2.2; p=0.005).
When patients were grouped into different severity classes based on PSI and CURB-65 scores, mortality rates were found to increase significantly as severity levels increased.
“In general, PSI was more sensitive than CURB-65 for mortality prediction among patients with CAP. [However], the sensitivity of PSI had a big drop from 100 to 80 percent at the class IV cutoff among patients aged 18 to 64 years, whereas it remained at 97 and 99 percent, respectively, in the other two patient groups,” researchers said.
Given that the best PSI cutoff score for mortality prediction was around 85 to 90 for younger patients, which was equivalent to PSI class III, researchers highlighted the indispensability of close monitoring and intensive clinical intervention in younger CAP patients even if the PSI severity level is not high. In elderly patients who may clinically present only with delirium or acute confusion instead of respiratory signs or symptoms, altered mental state is crucial in forecasting the high risk of death shortly after.
“The prognostic factors evaluated [in the present study] are all readily available when patients visit emergency departments. Clear awareness of these factors and understanding their predictive value would help physicians to predict the clinical outcome and customise the medical care being provided,” researchers said.
The study is not without limitations. Among those that researchers cited include the potentially reduced accuracy of data due to the retrospective design of the study and the possibility that the study might have been underpowered in terms of detecting some associations due to inadequacy of sample size for subgroup analyses.