Standardization of interstitial lung disease assessment by ultrasound: results from a Delphi process and web-reliability exercise by the OMERACT ultrasound working group.

OBJECTIVES: Over the last years ultrasound has shown to be an important tool for evaluating lung involvement, including interstitial lung disease (ILD) a potentially severe systemic involvement in many rheumatic and musculoskeletal diseases (RMD). Despite the potential sensitivity of the technique the actual use is hampered by the lack of consensual definitions of elementary lesions to be assessed and of the scanning protocol to apply. Within the Outcome Measures in Rheumatology (OMERACT) Ultrasound Working Group we aimed at developing consensus-based definitions for ultrasound detected ILD findings in RMDs and assessing their reliability in dynamic images. METHODS: Based on the results from a systematic literature review, several findings were identified for defining the presence of ILD by ultrasound (i.e., Am-lines, B-lines, pleural cysts and pleural line irregularity). Therefore, a Delphi survey was conducted among 23 experts in sonography to agree on which findings should be included and on their definitions. Subsequently, a web-reliability exercise was performed to test the reliability of the agreed definitions on video-clips, by using kappa statistics. RESULTS: After three rounds of Delphi an agreement >75 % was obtained to include and define B-lines and pleural line irregularity as elementary lesions to assess. The reliability in the web-based exercise, consisting of 80 video-clips (30 for pleural line irregularity, 50 for B-lines), showed moderate inter-reader reliability for both B-lines (kappa = 0.51) and pleural line irregularity (kappa = 0.58), while intra-reader reliability was good for both B-lines (kappa = 0.72) and pleural line irregularity (kappa = 0.75). CONCLUSION: Consensus-based ultrasound definitions for B-lines and pleural line irregularity were obtained, with moderate to good reliability to detect these lesions using video-clips. The next step will be testing the reliability in patients with ILD linked to RMDs and to propose a consensual and standardized protocol to scan such patients.

Quantitative ultrasound assessment of bone.

In the last two decades, several non-invasive techniques have been developed to measure bone density at axial and peripheral skeletal sites. The dual-energy X-ray absorptiometry (DXA) technique allows accurate measurement of bone density, but does not provide information about the structural and qualitative features of bone, which play an important role in fracture risk determination. Increasing interest in quantitative ultrasonography (QUS) has recently developed; it may be considered a safe and quite inexpensive diagnostic technique. Ultrasound devices routinely measure two parameters: broadband ultrasound attenuation (BUA) and speed of sound (SOS). Two other parameters, stiffness and index of consistency (QUI), can be derived from BUA and SOS. SOS is influenced by the elasticity of bone as well as by its density. BUA is determined by mechanisms of diffraction, scattering and absorption in the bone, marrow and soft tissue. Absorption predominates in cortical bone and scattering in trabecular bone. BUA is a measure of the approximately linear frequency dependence of ultrasound attenuation. Several QUS devices are now available for clinical use for measuring various parameters at skeletal sites with different contents of trabecular and cortical bone. Standardization of instruments is one of the major limitations of this technique today. Many studies have demonstrated that BUA and SOS, measured at any level, can discriminate normal subjects from osteoporotic patients. Moreover, there is evidence documenting the ability of QUS to predict osteoporotic fracture risk and to give further BMD-independent information on bone. QUS at the heel can now be considered as an alternative technique to identify subjects with a high risk of bone fragility. Further studies are needed for better definition of the role of QUS in clinical practice.