Fetal hemoglobin as a marker of maladaptation in community-acquired pneumonia in older adults

Background: Community-acquired pneumonia in older adults may act as a stress test that reveals limited adaptive reserve in the aging body. The search for laboratory markers capable of assessing the severity and duration of maladaptation remains an important interdisciplinary task at the intersection of clinical medicine and human ecology. Aim: This study aimed to evaluate etiology-specific changes in fetal hemoglobin over time as an indicator of erythropoietic stress in older patients with community-acquired pneumonia. Methods: This was a prospective, comparative study that included 85 patients aged 60 years and older with moderate community-acquired pneumonia (CURB-65 score 1–2): group 1, bacterial pneumonia (n = 30); group 2, COVID-19-associated pneumonia (n = 30); and group 3, influenza-associated pneumonia (n = 25). The control group consisted of 30 apparently healthy donors. Fetal hemoglobin concentration in erythrocyte hemolysates was measured using the Mancini radial immunodiffusion method at the peak of disease and at discharge. Statistical analysis was performed using the Shapiro–Wilk test, Kruskal–Wallis test (with Dunn post hoc test), Mann–Whitney test, and Wilcoxon test. Results: At the peak of disease, fetal hemoglobin levels were significantly elevated in all groups, reaching the highest values in bacterial pneumonia (4.2-fold higher than controls; p 0.001). In viral pneumonias (influenza- and COVID-19–associated), the increase was moderate (2.3–2.4-fold; p 0.01). At discharge, fetal hemoglobin levels in bacterial pneumonia were nearly normalized, whereas in influenza- and COVID-19-associated pneumonia, they remained persistently elevated (2.3-fold; p 0.001), not differing from values observed during the acute phase. Conclusion: Changes in fetal hemoglobin levels over time demonstrate pronounced etiology-specific patterns. Persistent elevation of fetal hemoglobin following viral pneumonias may serve as a potential marker of prolonged adaptive stress, likely reflecting incomplete recovery processes and indicating increased medical and ecological vulnerability of patients. These findings support the need for further prospective studies to evaluate the feasibility of fetal hemoglobin testing as a criterion for identifying patients at increased medical and ecological risk in the postinfectious period

Bacterial pneumonia · Etiology · Fetal hemoglobin · Hemoglobin · Hypoxemia · Pneumonia · Thalassemia · Venous blood · Blood groups and transfusion · Hemoglobinopathies and Related Disorders · Pneumonia and Respiratory Infections