Comparison of pulmonary function test, diffusion capacity, blood gas analysis and CT scan in patients with and without persistent respiratory symptoms following COVID-19

Background Long-lasting symptoms following SARS-CoV2-infection have been described in several studies. However, there is only limited knowledge about the ongoing pathophysiology and the association with pathological findings in medical examinations. Methods In this post hoc analysis of a prospective trial, 135 patients following COVID-19 were enrolled and grouped with respect to the presence or absence of respiratory ongoing symptoms following COVID-19. Pulmonary function test (PFT), diffusion capacity measurement (TLCO SB and TLCO/VA), blood gas analysis (BGA), laboratory tests and high-resolution computed tomography (HRCT) of patients with persistent respiratory symptoms were compared to those of asymptomatic patients. Results In this analysis, 71% (96/135) of all patients (mean age 49 years; range 20–91 years) reported long-lasting symptoms after a median (IQR) of 85 days (60–116) following COVID-19 whereby 57.8% (78/135) complained about persistent pulmonary symptoms. Pathological findings in blood test, PFT, TLCO, BGA and/or HRCT were found in 71.8% and 64.1% of patients with and without long-lasting respiratory symptoms respectively. Patients with persistent respiratory symptoms were significantly younger and presented a significant lower FVC (%), TLC (L), and TLCO SB compared to asymptomatic patients ( p < 0.05). The multiple logistic regression results in a significant effect of age (p = 0.004) and TLCO SB ( p = 0.042). Conclusion Following COVID-19, a large proportion of patients experience ongoing symptoms, whereby the respiratory symptoms are the predominant complaints. Compared to asymptomatic patients, patients with ongoing symptoms were younger and presented a significant lower FVC, TLC and TLCO SB. The multiple logistic regression demonstrated only a significant association between the TLCO SB as the only PFT parameter and the perceived symptoms.