The Cat Is Significantly Correlated to Dlco and 6-Minute Walk Test in Patients with Long-Covid

ABSTRACT

PURPOSE/HYPOTHESIS: Literature has reported some patients experience long-term impairments in pulmonary function following COVID-19 infection, with the most common abnormality being diffusing capacity for carbon monoxide (DLCO). Research on DLCO's association with other measures has been varied, with some studies demonstrating a significant association with older age, female gender, and disease severity, however these results are not consistent. In pulmonary patients, a DLCO of<40% or a drop in DLCO of >4 units is associated with increased morbidity and mortality, is an independent predictor of decreased exercise capacity, and predicts a more rapid decline in pulmonary function. In COPD patients, every 10% decrease in DLCO was associated with worsening quality of life (QOL), 6MWT, severe exacerbations, symptoms, and COPD assessment test (CAT) scores. CAT scores represent the general health status and include cough, sputum, energy, and ability to perform physical work. Daynes et al found an average of 52% of COVID-19 patients had high CAT scores (>10), which the GOLD guidelines suggest using as a cutoff to indicate symptomatic COPD. They found no significant association between CAT score and hospital length of stay or days on mechanical ventilation, but did find a moderately significant association to anxiety, depression, and self-reported physical activity levels.While a patient's pulmonary function test (PFT) may not be available to a clinician, the CAT is a quick and easy screening tool that can be performed in the clinic. The purpose of this study was to assess possible relationships between PFT measures and outcome assessments that can be performed in the clinic by a physical therapist (PT), which may aid in prognosis. NUMBER OF SUBJECTS: Sixteen subjects (8 male and 8 female with a mean age and BMI of 52 +/- 16 and 32 +/- 5, respectively) diagnosed with long-COVID and referred to pulmonary rehabilitation (PR). MATERIALS AND METHODS: Baseline PFT and CAT scores were obtained during the initial evaluation. Spearman's rho correlation analyses were performed. The 6MWT and DLCO were performed using standardized methods. RESULT(S) The baseline CAT, DLCO, and 6MWT were 22.2 +/- 6.7, 14.1 +/- 7.3 and 292 +/- 144 m, respectively. The CAT was significantly correlated to the DLCO (r-value of -0.63;P = .009) and 6MWT (r-value of -0.52;P = .04). CONCLUSION(S) Self-reported CAT scores were significantly correlated with DLCO and 6MWT in patients with long-COVID. CLINICAL RELEVANCE DLCO is the most common PFT abnormality observed in patients with long- COVID and can provide useful information to the clinician regarding prognosis and possibly disease severity. However, PTs may not have access to a patient's PFT report. Alternatively, a CAT assessment is free and quick and can be easily performed in the clinic.We found CAT scores were significantly correlated to DLCO and 6MWT, which may allow clinicians to use CAT scores as a surrogate measure to aid in establishing a prognosis and/or understanding of disease severity in patients with long-COVID.