Predictive factors for pneumonia mortality vary with age
The predictive value of different risk factors for mortality in pneumonia vary according to different age groups, a recent Singapore study has shown. Moreover, the Pneumonia Severity Index (PSI) appears to have a higher sensitivity than the CURB-65 (confusion, uraemia, respiratory rate ≥30 per minute, low blood pressure, age ≥65 years) measure.
Mortality rate was lowest in patients aged 18–64 years (n=614; 7.3 percent) and rose to 16.1 percent and 29.7 percent in those who belonged to the 65–84 and ≥85 years age brackets, respectively (p<0.001). The overall 30-day mortality rate was 15.7 percent, 85.3 percent of which were in-hospital while 14.7 percent occurred postdischarge. [Singapore Med J 2018;59:190-198]
In the 18–64 age group, malignancy (odds ratio [OR], 8.1; 95 percent CI, 4.0–16.6; p<0.001) and tachycardia (pulse rate ≥125/minute; OR, 4.3; 2.0–9.3; p<0.001) were significantly predictive of mortality. An arterial pH <7.3 showed borderline significant predictive value (OR, 2.8; 1.0–8.2; p=0.05).
Liver disease, dementia, chronic obstructive pulmonary disease and Parkinson’s disease were excluded from the analysis in the youngest age group due to low frequencies.
In patients aged 65–84 years, the male sex (OR, 2.0; 1.3–3.0; p=0.001), malignancies (OR, 2.8; 1.8–4.3; p<0.001), congestive heart failure (OR, 2.6; 1.4–4.7; p=0.003), altered mental status (OR, 3.3; 1.4–7.7; p=0.005), tachycardia (OR, 3.2; 1.8–5.6; p<0.001) and respiratory rate ≥30/minute (OR, 2.5; 1.2–5.3; p=0.02) significantly predicted mortality.
In the same age group, blood urea nitrogen ≥11 mmol/L (OR, 2.0; 1.3–3.1; p=0.002), serum sodium <130 mmol/L (OR, 1.7; 1.1–2.6; p=0.03), hypoxaemia (OR, 1.7; 1.1–2.9; p=0.03), arterial pH <7.35 (OR, 3.4; 1.8–6.5; p<0.001) and pleural effusion (OR, 2.6; 1.7–3.9; p<0.001) were also significantly predictive of mortality from pneumonia.
In patients ≥85 years of age, altered mental status (OR, 6.1; 2.1–17.3; p=0.001), tachycardia (OR, 2.5; 1.0–6.1; p=0.043), age (OR, 1.1; 1.03–1.17; p=0.006), blood urea nitrogen ≥11 mmol/L (OR, 2.0; 1.1–3.4; p=0.019), hypoxaemia (OR, 2.7; 1.3–5.7; p=0.009), arterial pH <7.35 (OR, 3.0; 1.1–8.4; p=0.03) and pleural effusion (OR, 2.2; 1.3–3.7; p=0.005) were the factors significantly associated with mortality.
Notably, in the oldest age group, asthma (OR, 0.1; 0.03–0.98; p=0.047) had a protective effect against pneumonia mortality.
“Asthmatic patients with [community-acquired pneumonia (CAP)] have been reported to present earlier to the hospital, are more often given antibiotic treatment before hospital admission, and generally have low CAP severity,” explained researchers. “All these may indicate that these patients are more aware of respiratory problems, even when symptoms are mild, and actively seek medical care earlier during the course of disease.”
For the study, researchers recruited 1,902 pneumonia patients who were then divided into the 18–64, 65–84 and ≥85 age groups. Multivariate logistic regression was performed for each age group to identify which of the 27 included prognostic factors were predictive of mortality.
Researchers also compared the PSI and CURB-65 indices in terms of predictive value and found that in general, PSI had a higher sensitivity than CURB-65. Receiver operator characteristic curve analysis showed that both PSI and CURB-65 decreased in accuracy as age increased, but that the area under the curve was higher in PSI than CURB-65 for each age group.