Clinical predictors of lung function in patients recovering from mild COVID-19

Abstract

Background: Few studies have assessed lung function in Hispanic subjects recovering from mild COVID-19. Therefore, we examined the prevalence of impaired pulmonary diffusing capacity for carbon monoxide (DLCO) as defined by values below the lower limit of normal (< LLN, < 5th percentile) or less than 80% of predicted in Hispanics recovering from mild COVID-19. We also examined the prevalence of a restrictive spirometric pattern as defined by the ratio of forced expiratory volume in 1 s (FEV₁) to forced vital capacity (FVC) being ≥ LLN with the FVC being < LLN. Finally, we evaluated previous studies to find factors correlated to impaired DLCO post-COVID-19.

Methods: In this observational study, adult patients (n = 146) with mild COVID-19 were recruited from a long-term follow-up COVID-19 clinic in Yucatan, Mexico, between March and August 2021. Spirometry, DLCO, and self-reported signs/symptoms were recorded 34 ± 4 days after diagnosis.

Results: At post-evaluation, 20% and 30% of patients recovering from COVID-19 were classified as having a restrictive spirometric pattern and impaired DLCO, respectively; 13% had both. The most prevalent reported symptoms were fatigue (73%), a persistent cough (43%), shortness of breath (42%) and a blocked/runny nose (36%). Increased age and a restrictive spirometric pattern increased the probability of having an impaired DLCO while having a blocked nose and excessive sweating decreased the likelihood. The proportion of patients with previous mild COVID-19 and impaired DLCO increased by 13% when the definition of impaired DLCO was < 80% predicted instead of below the LLN. When comparing previous studies, having severe COVID-19 increased the proportion of those with impaired DLCO by 21% compared to those with mild COVID-19.

Conclusions: One-third of patients with mild COVID-19 have impaired DLCO thirty-four days post-diagnosis. The criteria that define impaired DLCO and the severity of COVID-19 disease affects the proportion of those with impaired DLCO at follow-up. One-fifth of patients have a restrictive spirometric pattern.

Keywords: DLCO; Lung; Mexico; Respiratory function test; SARS-CoV-2.