Relation of pulmonary diffusing capacity changes to HRCT chest and V/Q SPECT findings at short-term and intermediate follow-up after COVID-19: a prospective cohort study (The secure study)

Background Several patients exhibit a severity-dependent reduced pulmonary diffusing capacity (D LCOc ) following coronavirus disease 2019 (COVID-19) infection. This has been attributed to fibrosis-like restrictive lung disease, as shown by chest high-resolution computed tomography (HRCT), and concurrent ventilatory disturbances observed by ventilation-perfusion single-photon emission computed tomography (V/Q SPECT) imaging. The aim of this study was to investigate whether reductions in D L,COc at short- and intermediate-term follow-up were associated with initial severity of COVID-19, and to which extend this was linked to the presence of fibrosis-like abnormalities on HRCT and ventilatory disturbances on V/Q SPECT. Methods A total of 153 patients diagnosed with COVID-19 between March 2020 and March 2021 were included in the study. The patients underwent lung function testing, chest HRCT, and V/Q SPECT at short-term (5.6 months) follow-up. Individuals exhibiting any evidence of post-COVID-19 sequelae ( n = 121) were also referred to intermediate follow-up (12.5 months). Results At short-term follow-up, a severity dependent reduction in D L,COc was observed, which was not evident at intermediate follow-up. At both short-term and intermediate follow-up, HRCT showed ground-glass opacity (GGO) and fibrosis-like abnormalities related to disease severity. Most patients had V/Q defects mainly with ventilatory abnormalities, including both matched and inversely matched defects at both follow-up times. Conclusion The severity-dependent reduction in D L,COc at short-term follow-up, associated with restrictive lung function pattern, GGO and fibrosis on HRCT, and ventilatory disturbances on V/Q SPECT, showed spontaneous recovery by intermediate follow-up. However, the restrictive ventilatory disturbances and associated morphological changes persisted.