Adaptation of liver stiffness measurement depth in bariatric surgery candidates with suspected nonalcoholic fatty liver disease

Fibroscan-Based Score to Predict Significant Liver Fibrosis in Morbidly Obese Patients with Nonalcoholic Fatty Liver Disease

BACKGROUND

The prevalence rate of nonalcoholic fatty liver disease (NAFLD) has been reported in 74 to 90% of morbidly obese patients. This study aims to develop a scoring system that predicts significant liver fibrosis in morbidly obese patients.

METHODS

This prospective cohort study involved 123 morbidly obese patients who underwent metabolic surgery at Taipei Medical University Hospital between October 2016 and June 2018. Wedge liver biopsy was performed during surgery, and significant liver fibrosis was defined as a fibrosis score ≧ 2. Ultrasonography and transient elastography were performed prior to surgery to assess the risk factors associated with significant liver fibrosis.

RESULTS

Mean patient age was 35.5 years, mean body mass index (BMI) was 40.6 kg/m2, and 87 (70.7%) were female. Fibrosis staging revealed 28 (22.8%) at stage 2, 14 (11.4%) at stage 3, and 2 (1.6%) at stage 4. Patients were then separated into training (n = 73) and validation (n = 50) cohorts. Multivariate analysis revealed a liver stiffness measurement (LSM) > 7 kPa and aspartate aminotransferase/platelet ratio index (APRI) > 0.40 as independent factors associated with significant liver fibrosis among the training cohort. Fibroscan-base score weighted sum of (1 for presence of APRI > 0.40) + (2 for presence of LSM > 7 kPa) yielded the highest area under receiver operating curve (0.854, P = 0.0001; 0.785, P = 0.0002) compared with other non-invasive markers in the training and validation cohorts, respectively.

CONCLUSION

We developed a simple, clinical scoring system incorporating Fibroscan and APRI to predict significant liver fibrosis in morbidly obese patients.

Adaptation of controlled attenuation parameter (CAP) measurement depth in morbidly obese patients addressed for bariatric surgery

Background and aim

The controlled attenuation parameter (CAP) using FibroScan (Echosens, Paris, France) M or XL probe has been developed for liver steatosis assessment. However, CAP performs poorly in patients with high body mass index. The aim of our study was to assess whether CAP is overestimated using the standard XL probe in patients with morbid obesity, and in the case of an overestimation, to reprocess the data at a greater depth to obtain the appropriate CAP (CAPa).

Patients and methods

We conducted an observational prospective cohort study on a total of 249 severely obese patients admitted to our institution to undergo sleeve gastrectomy. Patients had a liver biopsy performed during the surgery and a CAP measurement during the 15 days preceding biopsy. Patient files were reprocessed retrospectively by an algorithm, blinded to the patients’ clinical data. The algorithm automatically assessed the probe-to-capsula distance (PCD) by analysing the echogenicity of ultrasound signals on the time-motion mode. In the case of a distance >35 mm, the algorithm automatically selected a deeper measurement for CAP (CAPa). When PCD was less than 35 mm, the measured CAP was considered as appropriated (CAPa) and no further reprocessing was performed.

Results

CAP recording was not performed at a sufficient depth in 130 patients. In these patients, the CAPa obtained at the adapted depth was significantly lower than CAP (298±3.9 versus 340±4.2 dB/m; p< 0.0001) measured at the standard depth (35 to 75 mm). Multiple linear regression analysis revealed that both body mass index and hepatic steatosis were independently correlated with CAP values. After reprocessing the CAP in patients with PCD > 35 mm, steatosis stage was the only parameter independently correlated with CAP values. For the diagnosis of steatosis (S≥1), moderate to severe steatosis (S≥2) and severe steatosis (S = 3), the AUROC curves of CAPa (measured CAP in patients with PCD<35 mm and reprocessed CAP in those with PCD>35 mm) were 0.86, 0.83 and 0.79, respectively. The Obuchowski measure for the diagnosis of steatosis was 0.90±0.013.

Conclusion

CAP was overestimated in a half of morbidly obese patients using an XL probe, but CAP can be performed correctly in these patients after adapting the measurement depth.

Controlled attenuation parameter for diagnosing steatosis in bariatric surgery candidates with suspected nonalcoholic fatty liver disease

INTRODUCTION

Steatosis in patients with nonalcoholic fatty liver disease (NAFLD) is often benign, but may progress to fibrosis. The accurate diagnosis of hepatic steatosis is therefore important for clinical decision-making and prognostic assessments. The controlled attenuation parameter (CAP), a noninvasive measurement obtained with Fibro-Scan, has been developed for liver steatosis assessment. CAP performs poorly in patients with high BMI. The XL probe was initially developed for measuring liver stiffness in overweight patients. We assessed the diagnostic value of CAP in candidates for bariatric surgery with suspected NAFLD examined with the XL probe.

PATIENTS AND METHODS

For the retrospective group, raw ultrasonic radiofrequency signals were stored prospectively in the Fibro-Scan examination file for offline CAP calculation in 194 consecutive obese patients undergoing liver stiffness measurement in the 15 days before liver biopsy. For the prospective group, CAP was calculated automatically and prospectively from the XL probe in 123 obese patients.

RESULTS

In the retrospective group, the diagnostic accuracy of CAP was satisfactory for differentiating S3 from S0-S1-S2 (0.79±0.03; 95% confidence interval: 0.71-0.84) and S3 from S0 (0.85±0.05; 95% confidence interval: 0.73-0.92). The Obuchowski measure demonstrated a very good discriminatory performance: 0.87±0.02 in the retrospective group and 0.91±0.02 in the prospective group.

CONCLUSION

CAP calculations from XL probe measurements efficiently detected severe steatosis in morbidly obese patients with suspected NAFLD. However, the cutoff values should now be confirmed in a larger prospective cohort.