Radiological Patterns and Clinical Characteristics of Pneumococcal Pneumonia in Older Adults: A Retrospective Cohort Study
Background: Pneumococcal pneumonia is a major cause of mortality among the older adult population. Chest computed tomography (CT) findings can be broadly classified into three radiological types: alveolar, bronchopneumonia, and ground glass opacity (GGO) types. However, the clinical differences between these phenotypes remain poorly understood. This study aimed to clarify the clinical characteristics associated with each radiological type in patients aged 65 years and older. Methods: We retrospectively analyzed 184 patients hospitalized with pneumonia between April 1, 2011, and December 31, 2021, who tested positive for Streptococcus pneumoniae urinary antigen. Patients were classified into three groups based on chest CT findings: alveolar (n = 84), bronchopneumonia (n = 71), and ground-glass opacity type (n = 29). We compared the clinical features of these groups, including demographic characteristics, activities of daily living (ADL), inflammatory markers, and nutritional indicators. Results: ADL significantly deteriorated in all groups (Bowker’s test: alveolar, p = 0.046; bronchopneumonia, p < 0.001; GGO, p = 0.0498). Although the extent of decline did not differ significantly among the groups (Kruskal-Wallis test, p = 0.53), the pattern of changes in ADL tended to be different among the three types. The mortality rate was higher in the alveolar group (7 / 84, 8.3%) compared with the non-alveolar group (5 / 100, 5.0%) (Fisher’s exact test, p = 0.024). Procalcitonin (PCT) levels were significantly higher in the alveolar group than in the bronchopneumonia group (p = 0.04), while there was no significant difference in the nutritional findings. Conclusion: Among the three types of pneumococcal pneumonia, the alveolar type exhibited distinct clinical features, characterized by a higher frequency of COPD, increased mortality, and elevated PCT levels, compared with the other two types. In contrast, no significant differences were observed between the bronchopneumonia and ground-glass opacity patterns in the clinical findings investigated in this study.
