Abstract
Background and Aims
In recent years, point-of-care ultrasonography (POCUS) with lung ultrasonography (LUS) and inferior vena cava diameter (IVCD) measurements have attracted growing attention due to their capacity to estimate volume status in end-stage kidney disease (ESKD). There have been concerns about inter-operator reproducibility in POCUS, particularly the new user’s ability to distinguish varying lung pathologies on LUS accurately. For instance, lung diseases with thickening of subpleural structures, such as pulmonary fibrosis, can mimic LUS B-lines. B-lines are artefacts produced by extravascular lung water, which is summated into a B-line score (BLS). This study aims to investigate the ease of learning, and the inter-operator reproducibility of LUS and IVCD in an Asian haemodialysis (HD) cohort, in users with no prior ultrasound experience.
Method
A subgroup of 14 HD patients from the observational study by Teng et al comparing LUS and IVCD with other fluid assessment methods in a HD cohort, underwent LUS and IVCD pre- and post-HD with 2 operators in separate settings. LUS was performed via a 28-point protocol, while IVCD was measured in both inspiration (IVCDmin) and expiration (IVCDmax). IVCDi was calculated by indexing IVCD to body surface area. Study details are available elsewhere.
One operator was a Nephrologist experienced in ultrasonography who had done 150 previous studies, whilst the second operator was a Resident who had no prior exposure to POCUS. The Resident underwent 4 hours of instructional teaching including theory sessions, simulation and image interpretation. Images acquired by the Resident during the study were audited for interpretative accuracy, such as the ability to diagnose lung pathology accurately. The Resident was required to review the clinical presentations of all patients before making ultrasound diagnoses.
Results
392 lung images and 56 IVC images were acquired for 14 HD patients. 100% of patients’ clinical notes were reviewed prior to making ultrasound diagnosis. >98% of the diagnoses were correctly made, and only in 1 patient (7 lung images; case of bronchiectasis), was the ultrasonographic diagnosis incorrectly made of B-lines, although B-lines were seen in other lung fields in the same patient.
There was excellent inter-operator variability for BLS (r = 0.983, p < 0.001). There was moderate agreement between both operators in terms of BLS and by BLS categories (k = 0.586, p = 0.015 and k = 0.521, p = 0.010). In 14 independent LUS studies, only 1 reading demonstrated interobserver difference exceeding 1.96 standard deviation (SD).
There was also excellent inter-operator variability for IVCDimax (r = 0.994, p < 0.001) and IVCDimin. In 14 independent IVCDimax readings, 2 readings demonstrated interobserver difference exceeding 1.96 SD.
Conclusion
Point-of-care ultrasonography for volume assessment is able to demonstrate good inter-operator reproducibility and is easy for new users to learn. There is hence potential for more widespread incorporation of these volume assessment tools into community dialysis centres. POCUS has traditionally been performed by medical professionals, but in light of the relative ease of learning curve, it may be possible for allied healthcare professionals to acquire skills in POCUS.
Point of Care Ultrasonography for Objective Assessment of Heart Failure: Integration of Cardiac, Vascular, and Extravascular Determinants of Volume Status