Thoracic Ultrasound Refines Detection of ILD in Rheumatoid Arthritis

Thoracic ultrasound (TUS) combined with systematic screening for pre-defined respiratory symptoms may reduce the diagnostic delay in detecting rheumatoid arthritis-association interstitial lung disease (RA-ILD).¹

In the analysis, TUS examination accurately detected 82.6% of ILD cases, suggesting its applicability as a screening method to determine the need for further diagnostic workup for ILD, such as a chest high-resolution computed tomography (HRCT).

“Early identification of ILD should minimize the time of disease manifestation to treatment and, thereby, reduce the disease burden and treatment necessary to manage the lung disease and improve quality of life and overall survival,” wrote the investigative team, led by Bjørk K. Sofíudóttir, MD, department of rheumatology, Odense University Hospital.

A severe manifestation of RA, RA-ILD is present in approximately 2-10% of the patient population and demonstrates a 5-year mortality risk of 40%, compared with matched controls.² As a result, patients with RA are recommended to receive a diagnostic workup for ILD, with a chest HRCT and multi-disciplinary team (MDT) discussion considered the gold standard.³

However, although patients with RA are prone to lung diseases, including chronic obstructive pulmonary disease (COPD), there are no guidelines to screen for respiratory symptoms in RA.⁴ TUS has shown promising results in RA and other ILD populations, but it has not been validated as a screening method for undiagnosed RA-ILD.

The throrAcic UltRasOund in RA (AURORA) study was a prospective cross-sectional diagnostic test accuracy study with patient enrollment from June 2022 to May 2023.¹ Sofíudóttir and colleagues sought to determine the diagnostic accuracy of TUS in detecting ILD in RA patients with respiratory symptoms using chest HRCT combined with MDT.

Eligible patients were adults diagnosed with RA, assessed by an experienced rheumatologist, and presenting with respiratory symptoms, including dyspnea, cough, recurrent pneumonia, prior severe pneumonia, or a chest X-ray indicating interstitial abnormalities. A respiratory disease diagnosis other than ILD excluded a patient from the study, as did an HRCT in the previous 12 months.

TUS positive criteria included B-lines must be present in ≥2 zones with ≥10 B-lines in total or thickened and fragmented pleura in a minimum of 1 zone bilaterally. HRCT, the imaging reference standard for diagnosing ILD, was performed within 30 days after TUS. The sensitivity and specificity of TUS, comprising its positive predictive value (PPV) and negative predictive value, were the analysis’ primary outcomes.

Study participants were consecutively enrolled in outpatient clinics in rheumatology departments in four different hospitals in Southern Denmark. Ultimately, 80 participants with a positive screening were consecutively included in the study, of whom 77 received HRCT <30 days after TUS. A total of 23 (30%) participants were diagnosed with ILD, and TUS indicated ILD in 45 (58%) participants.

Upon analysis, TUS exhibited a sensitivity of 82.6% (95% CI, 61.2 - 95.0) and a specificity of 51.9% (95% CI, 37.8 - 65.7), with a diagnostic odds ratio (OR) of 5.12 (95% CI, 1.5 to 17.0). These results corresponded to a PPV of 42.2% (95% CI, 27.7 - 57.8) and an NPV of 87.5% (95% CI, 71.0 - 96.5).

Sofíudóttir and colleagues noted the increasing mortality rates in RA-ILD may be due to both the unawareness of the condition, as well as a delay in ILD diagnostics, often at late and severe stages of the lung disease. Evidence-based screening for the early initiation of diagnostics may be warranted to treat RA-ILD at earlier stages, including TUS.

“Using HRCT combined with MDT as a reference test for ILD, this study has validated TUS as a radiation-free bedside tool for triaging RA patients with respiratory symptoms for HRCT, with an NPV of 87.5%,” they wrote.

References

1. _{Sofíudóttir BK, Harders S, Laursen CB, et al. Detection of Interstitial Lung Disease in Rheumatoid Arthritis by Thoracic Ultrasound. A Diagnostic Test Accuracy study. Arthritis Care Res (Hoboken). Published online April 15, 2024. doi:10.1002/acr.25351}
2. _{Hyldgaard C, Hilberg O, Pedersen AB, Ulrichsen SP, Lokke A, Bendstrup E, et al. A population-based cohort study of rheumatoid arthritis-associated interstitial lung disease: comorbidity and mortality. Ann Rheum Dis. 2017;76(10):1700-6.}
3. _{Lynch DA, Sverzellati N, Travis WD, Brown KK, Colby TV, Galvin JR, et al. Diagnostic criteria for idiopathic pulmonary fibrosis: a Fleischner Society White Paper. Lancet Respir Med. 2018;6(2):138-53.4}
4. _{Hyldgaard C, Ellingsen T, Bendstrup E. COPD: an overlooked cause of excess mortality in patients with rheumatoid arthritis. Lancet Respir Med. 2018.}