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.