Reliability Criteria for Liver Stiffness Measurements with Real-Time 2D Shear Wave Elastography in Different Clinical Scenarios of Chronic Liver Disease

Abstract

Purpose Liver stiffness measurement by real-time 2-dimensional shear wave elastography (2D-SWE) lacks universal reliability criteria. We sought to assess whether previously published 2D-SWE reliability criteria for portal hypertension were applicable for the evaluation of liver fibrosis and cirrhosis, and to look for criteria that minimize the risk of misclassification in this setting.

Materials and Methods In a biopsy-controlled diagnostic study, we obtained five 2D-SWE measurements of optimal image quality. Correctly classified cases of fibrosis and cirrhosis were compared to misclassified cases. We compared reliability predictors (standard deviation (SD), SD/mean, size of region of interest (ROI) and difference between a single measurement and the patient’s median) with those obtained in a prior study on clinically significant portal hypertension.

Results We obtained 678 2D-SWE measurements from 142 patients. Overall, the variability in liver stiffness within single 2D-SWE measurements was low (SD = 1.1 ± 1.5kPa; SD/mean = 12 ± 9 %). Intra-observer analysis showed almost perfect concordance (intraclass correlation coefficient = 0.95; 95 % CI 0.94 – 0.96; average difference from median = 0.4 ± 0.9kPa). For the diagnosis of cirrhosis, a smaller SD (optimally ≤ 1.75 kPa) and larger ROI size (optimally ≥ 18 mm) were associated with higher accuracy. Similarly, within the published cohort of patients assessed for portal hypertension, a low variability of measurements was associated with high reliability.

Conclusion A high quality 2D-SWE elastogram ensures low variability and high reliability, regardless of indication. We recommend aiming for a combination of low standard deviation and large ROI.

Zusammenfassung

Ziel Bei Messung der Lebersteifigkeit mittels Echtzeit-2D-Shearwave-Elastografie (2D-SWE) fehlen allgemein gültige Reliabilitätskriterien. Wir waren bestrebt herauszufinden, inwieweit die zuvor publizierten 2D-SWE-Reliabilitätskriterien bei Pfortaderhochdruck auch bei der Bewertung der Leberfibrose und Zirrhose anwendbar sind und suchten nach Kriterien, das Risiko einer Falschdiagnose in diesem klinischen Umfeld zu minimieren.

Material und Methoden In einer zytologisch kontrollierten diagnostischen Studie erzielten wir fünf 2D-SWE-Messungen mit optimaler Bildqualität und korrekt klassifizierten Fibrose- und Zirrhosefälle wurden mit falsch klassifizierten Fällen verglichen. Wir verglichen Prädiktoren für Verlässlichkeit (Standardabweichung (SD), SD/Mittelwert, Größe der „region of interest“ (ROI) und Differenz zwischen Einzelmessung und Patientenmedian) mit denen in einer Vorgängerstudie bei klinisch signifikantem Pfortaderhochdruck erhobenen.

Ergebnisse Wir erhielten 678 2D-SWE-Messungen von 142 Patienten. Insgesamt war die Variabilität der Lebersteifigkeit innerhalb der einzelnen 2D-SWE-Messungen gering (SD = 1,1 ± 1,5 kPa; SD/Mittelwert = 12 ± 9 %); die Intraobserver-Analyse zeigte eine nahezu perfekte Übereinstimmung (Intraklasse-Korrelationskoeffizient = 0,95; 95 % CI 0,94 – 0,96; durchschnittliche Differenz zum Median = 0,4 ± 0,9 kPa). Bei der Diagnose einer Zirrhose war ein geringerer SD (optimal ≤ 1,75 kPa) und ein größerer ROI-Bereich (optimal ≥ 18 mm) mit einer höheren Genauigkeit assoziiert. Ähnlich wie in der publizierten Kohorte von Patienten mit Verdacht auf Pfortaderhochdruck bestand ein Zusammenhang zwischen geringerer Variabilität der Messungen und hoher Verlässlichkeit.

Schlussfolgerung Ein 2D-SWE-Elastogramm von hoher Qualität gewährleistet unabhängig von der Indikation niedrige Variabilität und hohe Verlässlichkeit. Wir empfehlen niedrige Standardabweichungen zusammen mit einer großen ROI anzustreben.

Key words

elastography - liver - aixplorer - quality criteria - supersonic shear imaging

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