CD4⁺ T cells related to disease severity in elderly and frailty community-acquired pneumonia patients: A retrospective cohort study

Backgrounds: Elderly and frailty individuals show a more senescent immune system, which may relate to worse outcome in community-acquired pneumonia (CAP). This study aimed to explore prognostic factors related to immune.Methods: Sixty of elderly (>= 65 years) and frailty (clinical frailty scale >= 5 scores) nonsevere CAP patients and 60 severe CAP (SCAP) patients were recruited at our center. Clinical and laboratory data, and several assessment scores were collected.Results: Compared with nonsevere CAP group, the elderly and frailty SCAP patients showed higher level of BMI, PaCO2 and lactate in arterial blood-gas, CURB-65 score, ICU admission, mechanical ventilation, shock accidence, and longer hospital stay using two-tailed t test. The SCAP group also showed increased CRP, IL-6, and PCT, and decreased CD3(+) T cells, CD4(+) T cells, and CD8(+) T cells. Logistic regression analysis showed that CD4(+) T cells, IL-6 and PCT were independent prognostic factors for SCAP. The area under the receiver operating characteristic (ROC) curve for CD4(+) T cells combined with PCT was 0.771 (95% CI 0.683-0.859), and the sensitivity and specificity were both 76.7%. Paired t test analysis showed that low CD4(+) T cells in SCAP patients increased after treatment.Conclusions: CD4(+) T cells decreased in elderly and frailty SCAP patients, and CD4(+) T cells combined with PCT were relatively accurate in the prediction of elderly and frailty SCAP.