What is the impact of changing body position on liver stiffness estimates obtained using point shearwave elastography in fasted healthy volunteers?
Suman Bassi1, Anne-Marie Culpan2, Kirstie Godson2, 1Philips Clinical Applications Specialist, 2University of Leeds
Aim:
To investigate the effect of changing posture on liver stiffness elastography measurements (LSEM) obtained using Point Shear-wave Elastography (PSWE) in healthy volunteers.
Materials and Methods
Sixteen self-selecting healthy volunteers with BMI < 30 kgm-2 were fasted for at least 3 hours before being examined by a single operator using an Affiniti 70 Philips® system with C5-1 curvi-linear transducer. Ten LSEM (kPa) were performed with participants in standard supine (control), left lateral decubitus (LLD) (experimental 1) and semi-erect (SE) (experimental 2) positions. The right lobe of liver was accessed intercostally on neutral breath hold. Data analysis of the mean LSEM using both Bland Altman assessment for agreement and paired sample T-tests to compare control values with each of the two experimental positions was performed.
Results
Median age: 37 years (range 22-61); median BMI 22.2kgm-2 (range 17-28). LSEM mean (SD) and median (range) in kPa: Supine: 4.66 (0.85), 4.66 (3.22-6.95); LLD: 4.80 (1.06), 4.65 (3.40-6.95); semi-erect: 5.26 (1.42), 5.23 (2.87-7.68).
Experiment 1 resulted in mean difference 0.14, p=0.593 (95% CI -0.41 - 0.69); Experiment 2 showed mean difference 0.59, p=0.027 (95% CI 0.07- 1.11). Bland Altman analysis indicates 95% limits of agreement for experiment 1 (2.22 to -1.98) and experiment 2 (2.5 to -1.3).
Conclusion
Both experimental postures showed increased variability in LSEM relative to supine control. No statistically significant difference for supine v LLD suggests these postures are interchangeable in clinical practice; statistically significant difference for SE posture suggests this could lead to higher liver stiffness grading, up to 1kPa. Although small mean differences, the wide LoA (approx. 2kPa) for both experimental postures could have clinical impact particularly in mild/moderate fibrosis categories due to narrower cut-off ranges. Results suggest measurements should be performed in supine posture where possible, or same posture maintained for patients undergoing serial surveillance scans.
Please note I have done this MSc study whilst employed by Philips as an Applications Specialist, but this study has not been sponsored by Philips.