Background

NHLC patients typically have no structural cause on chest CT to explain their symptoms.

Aims

EXPLAIN is a multi-centre, prospective, observational, cohort study comparing Lung Function Tests (LFT), dyspnoea scores and hyperpolarised 129Xe MRI in dyspnoeic and non-dyspnoeic NHLC patients and asymptomatic post-COVID controls. Here, we present the LFT interim analysis of 116 participants. 

Methods

NHLC patients were recruited from post-COVID clinics. Participants with significant smoking history and cardiorespiratory diseases were excluded from the study. The median time from infection was 463, 235, and 202 days in dyspnoeic NHLC patients, non-dyspnoeic NHLC patients and controls respectively.

Results

All participants had normal or near-normal chest CT. At least 89% of participants were Caucasians in each group (p=0.5).

Although within normal limits, FVC (101 vs 109%predicted, p=0.007) and DLCO (94 vs 102%predicted, p=0.013) were significantly lower in the breathless group compared with the control group.

Conclusion

Preliminary data suggests unexplained lower FVC %predicted and DLCO %predicted seen in NHLC breathless patients with no associated CT abnormalities beyond a year of mild COVID-19 infection compared with fully recovered controls. We aim to use 129Xe MRI to elucidate the underlying mechanisms contributing to these observed differences.