Post-COVID-19 lung disease: utility of biochemical and imaging markers in uncovering residual lung inflammation and monitoring anti-inflammatory therapy, a prospective study.

Abstract

Post-COVID-19 lung disease (PCLD) is a significant concern following the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. PCLD encompasses persistent debilitating respiratory symptoms and radiological changes beyond the acute disease phase. It highlights the ongoing search to identify and manage lingering diseases. This prospective study utilizes F18-Fludeoxyglucose (FDG) PET/CT to identify residual inflammatory lung lesions in PCLD. Treatment response was assessed after anti-inflammatory and antifibrotic therapies. Thirty patients post-severe COVID-19 pneumonia enrolled. They underwent baseline ¹⁸F-FDG PET/CT scans to unveil residual lung inflammation lesions on FDG and CT. They received antifibrotic (Pirfenidone) and anti-inflammatory (Methylprednisolone) drugs for 6-12 weeks. They were followed up for clinical, biochemical, and imaging treatment responses. Baseline ¹⁸F-FDG PET/CT revealed ongoing lung inflammation in all PCLD (mean SUV_max: 3.8 ± 2.3 and number of segments: 8±3 ). The mean CT severity score was 17.7 ± 3.4 with moderate (n = 16) or severe (n = 14) disease involvement. Mild, moderate, and severe ¹⁸F-FDG PET/CT categories were noted in the 8, 14, and 8 patients, respectively. Following treatment, a PET scan showed a significant decrease in disease extent (segments) and severity (FDG uptake) and an improvement in disease grading on imaging (97% of patients). In PET concordance, there was a significant clinical and radiological improvement with a fall in inflammatory markers (p < 0.005). Serum Ferritin and total leukocyte counts were significantly associated with PCLD severity on ¹⁸F-FDG PET/CT(p < 0.05). This prospective study identifies and quantifies ongoing significant residual lung inflammation in PCLD on ¹⁸F-FDG PET/CT. Anti-inflammatory and antifibrotic drug therapy led to clinical and radiological improvement. ¹⁸F-FDG PET/CT as a non-invasive biomarker helped manage and follow up PCLD patients. Not applicable.