Development and Validation of a Predictive Model of Success in Bariatric Surgery

Presurgery health influences outcomes following vertical sleeve gastrectomy in adolescents

OBJECTIVE

Weight loss following vertical sleeve gastrectomy (VSG) in youth can range from 10% to 50%. We examined whether there are differences in demographic or metabolic parameters before VSG in youth who achieve above-average weight loss (AAWL) versus below-average weight loss (BAWL) at 1 year post VSG and if youth with BAWL still achieve metabolic health improvements at 1 year post VSG.

METHODS

Demographic, anthropometric, and clinical lab data were collected before VSG and at 1, 3, 6, and 12 months after VSG.

RESULTS

Forty-three youth with a mean age of 16.9 (SD 1.7) years before VSG were studied; 70% were female, 19% non-Hispanic Black, 58% non-Hispanic White, and 23% mixed/other race. Mean baseline BMI was 51.1 (SD 10.5) kg/m2. Average weight loss was 25.8%. The AAWL group lost 18.6 kg/m2 (35.3%) versus the BAWL group, who lost 8.8 kg/m2 (17.5%). BMI, age, race, sex, and socioeconomic status at baseline were similar between AAWL and BAWL groups; however, the BAWL group had a higher frequency of pre-VSG dysglycemia, steatotic liver disease, and dyslipidemia. At 1 year post VSG, fewer youth in the BAWL group achieved ideal health parameters, and they had less resolution of comorbidities.

CONCLUSIONS

The presence of comorbidities before VSG is associated with less weight loss and reduced resolution of metabolic conditions at 1 year post VSG.

Developing a Decision Aid for Clinical Obesity Services in the Real World: the DACOS Nationwide Pilot Study

PURPOSE

The purpose of this study is to develop a decision aid tool using "real-world" data within the Australian health system to predict weight loss after bariatric surgery and non-surgical care.

MATERIALS AND METHODS

We analyzed patient record data (aged 16+years) from initial review between 2015 and 2020 with 6-month (n=219) and 9-/12-month (n=153) follow-ups at eight clinical obesity services. Primary outcome was percentage total weight loss (%TWL) at 6 months and 9/12 months. Predictors were selected by statistical evidence (p<0.20), effect size (±2%), and clinical judgment. Multiple linear regression and bariatric surgery were used to create simple predictive models. Accuracy was measured using percentage of predictions within 5% of the observed value, and sensitivity and specificity for predicting target weight loss of 5% (non-surgical care) and 15% (bariatric surgery).

RESULTS

Observed %TWL with bariatric surgery vs. non-surgical care was 19% vs. 5% at 6 months and 22% vs. 5% at 9/12 months. Predictors at 6 months with intercept (non-surgical care) of 6% include bariatric surgery (+11%), BMI>60 (-3%), depression (-2%), anxiety (-2%), and eating disorder (-2%). Accuracy, sensitivity, and specificity were 58%, 69%, and 56%. Predictors at 9/12 months with intercept of 5% include bariatric surgery (+15%), type 2 diabetes (+5%), eating disorder (+4%), fatty liver (+2%), atrial fibrillation (-4%), osteoarthritis (-3%), sleep/mental disorders (-2-3%), and ≥10 alcohol drinks/week (-2%). Accuracy, sensitivity, and specificity were 55%, 86%, and 53%.

CONCLUSION

Clinicians may use DACOS to discuss potential weight loss predictors with patients after surgery or non-surgical care.

Machine learning models to predict success of endoscopic sleeve gastroplasty using total and excess weight loss percent achievement: a multicentre study

BACKGROUND

The large amount of heterogeneous data collected in surgical/endoscopic practice calls for data-driven approaches as machine learning (ML) models. The aim of this study was to develop ML models to predict endoscopic sleeve gastroplasty (ESG) efficacy at 12 months defined by total weight loss (TWL) % and excess weight loss (EWL) % achievement. Multicentre data were used to enhance generalizability: evaluate consistency among different center of ESG practice and assess reproducibility of the models and possible clinical application. Models were designed to be dynamic and integrate follow-up clinical data into more accurate predictions, possibly assisting management and decision-making.

METHODS

ML models were developed using data of 404 ESG procedures performed at 12 centers across Europe. Collected data included clinical and demographic variables at the time of ESG and at follow-up. Multicentre/external and single center/internal and temporal validation were performed. Training and evaluation of the models were performed on Python's scikit-learn library. Performance of models was quantified as receiver operator curve (ROC-AUC), sensitivity, specificity, and calibration plots.

RESULTS

Multicenter external validation: ML models using preoperative data show poor performance. Best performances were reached by linear regression (LR) and support vector machine models for TWL% and EWL%, respectively, (ROC-AUC: TWL% 0.87, EWL% 0.86) with the addition of 6-month follow-up data. Single-center internal validation: Preoperative data only ML models show suboptimal performance. Early, i.e., 3-month follow-up data addition lead to ROC-AUC of 0.79 (random forest classifiers model) and 0.81 (LR models) for TWL% and EWL% achievement prediction, respectively. Single-center temporal validation shows similar results.

CONCLUSIONS

Although preoperative data only may not be sufficient for accurate postoperative predictions, the ability of ML models to adapt and evolve with the patients changes could assist in providing an effective and personalized postoperative care. ML models predictive capacity improvement with follow-up data is encouraging and may become a valuable support in patient management and decision-making.

Development of the national bariatric prioritization tool in Aotearoa New Zealand

BACKGROUND

Bariatric surgery is a proven effective method of reducing obesity and reversing or preventing obesity-related comorbidities. The aim of this study is to describe the development of a tool to assist with the prioritization of patients with obesity for bariatric surgery. The tool would meet the criteria for being evidence-based, fair, implementable and transparent.

METHODS

The development of the tool involved a validated step-by-step process based on the consensus of clinical judgement of the New Zealand Ministry of Health working party. The process involved elicitation of criteria, clinical ranking of vignettes and creation of weightings using the 1000Minds® tool. The concurrent validity was tested by comparing tool rankings of vignettes to clinical judgement rankings.

RESULTS

Four major criteria (impact on life, likelihood of achieving maximum benefit with respect to control of diabetes, duration of benefit and surgical risk) are used to characterize the need and potential to benefit. The impact on life criterion has the largest weighting (up to 44.3%). There was good concurrent validity with a correlation coefficient r = 0.67.

CONCLUSION

The tool as presented is evidence-based, transparent and internally valid. The next step is to assess the predictive validity of the tool using real patient data to evaluate the effectiveness of the tool and determine what modifications may be required.

Constructing and Validating a Dynamic Nomogram to Predict Response to Bariatric Surgery: A Multicenter Retrospective Study

PURPOSE

Suboptimal response is one of the major problems for bariatric surgery, and constructing an individualized model for predicting outcomes of bariatric surgery is essential. Thus, the aim of this study is to develop a nomogram to predict the response to bariatric surgery.

MATERIALS AND METHODS

509 patients who underwent bariatric surgery between 2019 to 2020 from 6 centers were retrieved and assessed. Multiple Imputation was used to replace missing data. Patients with %TWL ≥ 20% 1 year after bariatric surgery were classified as patients with optimal response, while the others were patients with suboptimal response. A web-based nomogram was constructed and validated. ROC curve and calibration curve were used to determine the predictive ability of our model.

RESULTS

56 (11.0%) patients were classified as patients with suboptimal response, and they showed advanced age, lower pre-operative BMI, smaller waist circumference, higher fasting glucose, higher HbA1c and lower fasting insulin compared to patients with optimal response. A forward likelihood ratio logistic regression analysis indicated that age (OR = 0.943, 95% CI: 0.915-0.971, p < 0.001), pre-operative BMI (OR = 1.109, 95% CI: 1.002-1.228, p = 0.046) and waist circumference (OR = 1.043, 95% CI: 1.000-1.088, p = 0.048) were essential factors contributing to the response to bariatric surgery. Lastly, a web-based nomogram was constructed to predict the response to bariatric surgery and demonstrated an AUC of 0.829 and 0.798 upon internal and external validation.

CONCLUSION

Age, BMI and fasting glucose were proved to be essential factors influencing the response to bariatric surgery. The nomogram constructed in this study demonstrated good adaptivity.

Distinct adaptations of endocrine and cognitive functions may contribute to high variability in long-term weight loss outcome after bariatric surgery

BACKGROUND

Bariatric surgery has been widely recognized as the most efficient long-term treatment method in severe obesity, yet therapy success shows considerable interindividual variability. Postoperative metabolic adaptations, including improved gut hormone secretion (GLP-1, PYY and ghrelin), and restored executive function may play an explanatory role in weight loss, yet causes for poor success in individual patients remain unknown. This study investigates gut-hormonal and cognitive characteristics in extreme weight loss responders to bariatric surgery.

METHODS

Patients (n=47) with high or low excessive weight loss (EWL) at least 2 years after Roux-en-Y-gastric bypass or sleeve gastrectomy were allocated into good responders (GR, EWL 82.4 ± 11.6%) and poor responders (PR, EWL 24.0 ± SD 12.8%) to study differences in postprandial secretion of GLP-1, PYY, ghrelin and in working memory (WM).

RESULTS

Mean BMI was 47.1 ± 6.2 kg/m² in PR (n=21) and 28.9 ± 3.1 kg/m² in GR (n=26, p < 0.001). Fasted GLP-1 and PYY were comparable for GR and PR (p > 0.2) and increased strongly after a standardized test meal (300 kcal liquid meal) with a peak at 15 to 30 minutes. The increase was stronger in GR compared to PR (GLP-1, PYY: Time x Group p < 0.05). Plasma ghrelin levels already differed between groups at fasted state, showing significantly higher levels for GR (p < 0.05). Postprandially, ghrelin secretion was suppressed in both groups, but suppression was higher in GR (Time x Group p < 0.05). GR showed significantly higher WM scores than PR (p < 0.05). Postprandial ghrelin (iAUC), but not GLP-1 or PYY plasma levels, significantly mediated the relationship between EWL and a WM subscore (IS score, CI = 0.07 - 1.68), but not WM main score (MIS score, CI = -0.07 - 1.54), in mediation analyses.

CONCLUSION

Excess weight loss success after bariatric surgical procedures is associated with distinct profiles of gut-hormones at fasted and postprandial state, and differences in working memory. Better working memory performance in GR might be mediated by higher postprandial reduction in ghrelin plasma levels. Future studies need to integrate longitudinal data, larger samples and more sensitive cognitive tests.

How Good is Stratification and Prediction Model Analysis Between Primary and Revisional Roux-en-Y Gastric Bypass Surgery? A Multi-center Study and Narrative Review

INTRODUCTIONS

Revision surgery because of weight recurrence is performed in 2.5-33% of primary vertical banded gastroplasty (VBG), laparoscopic sleeve gastrectomy (LSG), and gastric band (GB) cases. These cases qualify for revisional Roux-en-Y gastric bypass (RRYGB).

METHODS

This retrospective cohort study analyzed data from 2008 to 2019. A stratification analysis and multivariate logistic regression for prediction modeling compared the possibility of sufficient % excess weight loss (%EWL) ≥ 50 or insufficient %EWL < 50 between three different RRYGB procedures, with primary Roux-en-Y gastric bypass (PRYGB) as the control during 2 years of follow-up. A narrative review was conducted to test the presence of prediction models in the literature and their internal and external validity.

RESULTS

A total of 558 patients underwent PRYGB, and 338 underwent RRYGB after VBG, LSG, and GB, and completed 2 years of follow-up. Overall, 32.2% of patients after RRYGB had a sufficient %EWL ≥ 50 after 2 years, compared to 71.3% after PRYGB (p ≤ 0.001). The total %EWL after the revision surgeries for VBG, LSG, and GB was 68.5%, 74.2%, and 64.1%, respectively (p ≤ 0.001). After correcting for confounding factors, the baseline odds ratio (OR) or sufficient %EWL ≥ 50 after PRYGB, LSG, VBG, and GB was 2.4, 1.45, 0.29, and 0.32, respectively (p ≤ 0.001). Age was the only significant variable in the prediction model (p = 0.0016). It was impossible to develop a validated model after revision surgery because of the differences between stratification and the prediction model. The narrative review showed only 10.2% presence of validation in the prediction models, and 52.5% had external validation.

CONCLUSION

Overall, 32.2% of all patients after revisional surgery had a sufficient %EWL ≥ 50 after 2 years, compared to PRYGB. LSG had the best outcome in the revisional surgery group in the sufficient %EWL group and the best outcome in the insufficient %EWL group. The skewness between the prediction model and stratification resulted in a partially non-functional prediction model.

Microvesicular Steatosis in Individuals with Obesity: a Histological Marker of Non-alcoholic Fatty Liver Disease Severity

BACKGROUND

In non-alcoholic fatty liver disease (NAFLD), steatosis can manifest through two distinct forms: macrovesicular (macroS) and microvesicular (microS).

OBJECTIVE

To investigate the prevalence of microS and its association with biochemical parameters and NAFLD-related histological findings in individuals with obesity.

METHODS

This is an observational retrospective cross-sectional study, enrolling individuals who underwent bariatric surgery and liver biopsy at a university hospital. A 1:2 propensity matching was performed to pair microS with isolated macroS; this matching enrolled variables "age," "gender," "body mass index (BMI)," and "obesity-associated medical problems." Clinical, biochemical, and histopathological aspects were then analyzed and compared.

RESULTS

Of 115 participants, 88.7% were female; average age was 40.5 ± 5 years and mean BMI was 37.9 ± 3.3 kg/m². Steatosis occurred in 82.6% (67.8% isolated macroS and 14.8% microS). MicroS is significantly associated with higher levels of alanine aminotransferase (ALT) (39.8 ± 26.4 vs. 26.7 ± 17.5; p = 0.04) and glucose (103.8 ± 52.6 vs. 83.3 ± 10.8; p = 0.03) and higher frequencies of moderate to severe macroS (41.2% vs. 2.0%; p < 0.001), portal fibrosis (100% vs. 50%; p < 0.001), perisinusoidal fibrosis (100% vs. 55.9%; p < 0.001), lobular inflammation (100% vs. 41.1%; p < 0.001), and portal inflammation (100% vs. 41.1%; p < 0.001). An independently positive association was observed between intensities of microS and macroS (p < 0.001).

CONCLUSION

MicroS is significantly associated with higher levels of ALT and glucose and higher frequencies of moderate to severe macroS, hepatocellular ballooning, portal fibrosis, perisinusoidal fibrosis, lobular inflammation, and portal inflammation. These findings indicate that microS could be considered a reliable histological marker of NAFLD severity.

Long-term Engagement in Physical Activity Among Bariatric Surgery Patients: Associations with Treatment Outcomes at 5-Year Follow-up

PURPOSE

Physical activity studies involving bariatric surgery patients tend to be short-term or cross-sectional investigations. Longer-term studies are limited and typically consist of relatively brief objective measurement periods used to generalize activity patterns. Very little research combines objective measurements with structured interviews to determine both the patterns and related factors of long-term physical activity among patients undergoing bariatric surgery.

MATERIALS AND METHODS

Previous volunteers in a perioperative physical activity study were invited to participate in a mixed methods study investigating physical activity among bariatric patients over a 5-year postoperative period. Fifty-one patients (M_age = 45.4 years; 76.5% female, 90.2% White; 86.3% Roux-en-Y procedure) provided interview, survey, accelerometer, and anthropometric data.

RESULTS

Participants were divided into four exercise quartiles, based on self-report of their length of regular exercise involvement from 1 year before through 5 years after surgery. Those reporting the most periods of regular exercise took the most measured steps per day, had greater moderate-to-vigorous physical activity and more bout-related activity, experienced the largest decrease in BMI, and reported the most adherence to nutritional guidelines. Participants reporting the most and least physical activity found the measurement periods to be most similar to their normal activity patterns. While physical activity increased significantly after surgery, measured physical activity did not reach recommended levels for steps or exercise bout minutes.

CONCLUSIONS

Measured physical activity and self-reported physical activity show congruent trends among patients undergoing bariatric surgery. More research is needed to determine optimal long-term monitoring and promotion of physical activity among patients.

Advice of General Practitioner, of Surgeon, of Endocrinologist, and Self-determination: the Italian Road to Bariatric Surgery

PURPOSE

Bariatric surgery (BS) is considered the most efficient treatment for severe obesity. International guidelines recommend multidisciplinary approach to BS (general practitioners, endocrinologists, surgeons, psychologists, or psychiatrists), and access to BS should be the final part of a protocol of treatment of obesity. However, there are indications that general practitioners (GPs) are not fully aware of the possible benefits of BS, that specialty physicians are reluctant to refer their patients to surgeons, and that patients with obesity choose self-management of their own obesity, including internet-based choices. There are no data on the pathways chosen by physicians and patients to undergo BS in the real world in Italy.

METHODS

An exploratory exam was performed for 6 months in three pilot regions (Lombardy, Lazio, Campania) in twenty-three tertiary centers for the treatment of morbid obesity, to describe the real pathways to BS in Italy.

RESULTS

Charts of 2686 patients (788 men and 1895 women, 75.5% in the age range 30-59 years) were evaluated by physicians and surgeons of the participating centers. A chronic condition of obesity was evident for the majority of patients, as indicated by duration of obesity, by presence of several associated medical problems, and by frequency of previous dietary attempts to weight loss. The vast majority (75.8%) patients were self-presenting or referred by bariatric surgeons, 24.2% patients referred by GPs and other specialists. Self-presenting patients were younger, more educated, more professional, and more mobile than patients referred by other physicians. Patients above the age of 40 years or with a duration of obesity greater than 10 years had a higher prevalence of all associated medical problems.

CONCLUSIONS

The majority of patients referred to a tertiary center for the treatment of morbid obesity have a valid indication for BS. Most patients self-refer to the centers, with a minority referred by a GP or by specialists. Self-presenting patients are younger, more educated, more professional, and more mobile than patients referred by other physicians. Older patients and with a longer duration of obesity are probably representative of the conservative approach to BS, often regarded as the last resort in an endless story.

Polysomnography in pre-operative screening for obstructive sleep apnea in patients undergoing bariatric surgery: a retrospective cohort study

BACKGROUND/OBJECTIVES

To assess the impact of obstructive sleep apnea (OSA) screening with polysomnography on preventing cardiovascular and pulmonary complications in the postoperative period of bariatric surgery.

SUBJECTS/METHODS

This was a single-center retrospective cohort study, including 522 adults who underwent bariatric surgery between August 2010 and May 2019. Electronic medical records were accessed to obtain variables of interest. Screening for OSA was performed as a medical indication and registered as positive if apnea-hypopnea index was ≥5 events/hour in patients who did not have previous OSA diagnosis. The primary outcome was the presence of cardiac or pulmonary events in the 30-day postoperative period. Secondary outcomes included length of stay (days), need for an intensive care unit (ICU) after surgery, length of mechanical ventilation, and time from mechanical ventilation withdrawal. Statistical analyses were performed with χ², Fisher's exact test, Student's t-test, Mann-Whitney U test, and Poisson regression.

RESULTS

Most participants (n = 326) did not have OSA screening with polysomnography, while 196 had performed this screening. There was no difference in cardiopulmonary events between the screening and non-screening groups (4.2% vs. 2.8%; P = 0.45). Polysomnography screening could not reduce cardiovascular or pulmonary complications in the postoperative period, RR = 1.73 (95% CI: 0.68-4.14). There was no difference in ICU admission, length of stay, and time from mechanical ventilation between groups in secondary outcomes.

CONCLUSIONS

Our study suggests that OSA screening with polysomnography in the pre-operative care of bariatric surgery is a dispensable procedure, as it does not change postoperative cardiopulmonary outcomes. Indications for polysomnography should be made at the individual level.

Evaluation of Stomatognathic System Parameters After Bariatric Surgery

PURPOSE

The present study aimed to evaluate electromyographic activity, bite strength, and masticatory muscle thickness in women without obesity and with severe obesity elected for bariatric surgery. Also, patients with obesity underwent bariatric surgery and were re-evaluated 3 and 6 months after surgery to analyze the influence of bariatric surgery outcomes on the stomatognathic system, a functional anatomical system comprising teeth, jaw, and associated soft tissues.

MATERIAL AND METHODS

Thirty-seven women were enrolled in the study. Twenty-one women with class II and III obesity according to the body mass index (BMI) and eligible for bariatric surgery composed the obesity pre-surgery group (Ob). Sixteen women with a normal weight according to BMI composed the non-obesity group (NOb). Afterward, the patients from the Ob group were followed up for 3 and 6 months after undergoing Roux-en-Y gastric bypass. Anthropometry, body composition, and parameters of the stomatognathic system were evaluated.

RESULTS

The stomatognathic system of the Ob group had less muscle activity and bite strength, but the thickness of masseter and temporal muscles was larger than the NOb group. We also observed a significant change in the muscular activity and bit strength of the stomatognathic system post-bariatric surgery.

CONCLUSION

Evaluating the stomatognathic system indicated that women with clinically severe obesity have less masticatory efficiency than non-obese. Also, we found a positive influence of bariatric surgery in masticatory activity after 3 and 6 months. Thus, monitoring the parameters of the stomatognathic system could be important in the indication and outcomes of bariatric surgery.

Accuracy of ultrasound diagnosis of nonalcoholic fatty liver disease in patients with classes II and III obesity: A pathological image study

Liver biopsy is the gold standard method to diagnose nonalcoholic fatty liver disease (NAFLD). However, ultrasound is widely recommended as the first-line imaging test for individuals with suspected NAFLD. This study aimed to estimate the accuracy of ultrasound as a screening test for NAFLD compared to liver biopsy in a cohort of patients with class II and III obesity undergoing bariatric surgery. This retrospective study included patients undergoing Roux-en-Y gastric bypass in southern Brazil between 2010 and 2019 who were screened for NAFLD with both ultrasound and liver biopsy. All samples were collected by a core biopsy needle and were analyzed by the same pathologist. Sensitivity, specificity, and positive and negative predictive values of ultrasound were estimated. The final database included 227 patients, mostly female (84%) and white (83.6%), with a mean age of 42.5 ± 10.2 years and a mean preoperative body mass index of 49.5 ± 8.4 kg/m². A total of 153 subjects (67.4%) were diagnosed with NAFLD through liver biopsies: 41 (18%) had fatty liver and 112 (49.3%) had nonalcoholic steatohepatitis. Ultrasound sensitivity was 88.9% and specificity was 44.6%. Positive and negative predictive values were 76.8% and 66.0%, respectively. Positive likelihood ratio was 1.6 (95% CI 1.30-1.98), and negative likelihood ratio was 0.25 (95% CI 0.15-0.42). Therefore, approximately three every four subjects with an ultrasound suggesting NAFLD were true positives. Ultrasound showed a good sensitivity in detecting NAFLD in patients with class II and III obesity.

Cost-effectiveness of bariatric and metabolic surgery, and implications of COVID-19 in the United Kingdom

Background

People living with obesity have been among those most disproportionately impacted by the COVID-19 pandemic, highlighting the urgent need for increased provision of bariatric and metabolic surgery (BMS).

Objectives

To evaluate the possible clinical and economic benefits of BMS compared with nonsurgical treatment options in the UK, considering the broader impact that COVID-19 has on people living with obesity.

Setting

Single-payer healthcare system (National Health Service, England).

Methods

A Markov model compared lifetime costs and outcomes of BMS and conventional treatment among patients with body mass index (BMI) ≥ 40 kg/m², BMI ≥ 35 kg/m² with obesity-related co-morbidities (Group A), or BMI ≥ 35 kg/m² with type 2 diabetes (T2D; Group B). Inputs were sourced from clinical audit data and literature sources; direct and indirect costs were considered. Model outputs included costs and quality-adjusted life years (QALYs). Scenario analyses whereby patients experienced COVID-19 infection, BMS was delayed by five years, and BMS patients underwent endoscopy were conducted.

Results

In both groups, BMS was dominant versus conventional treatment, at a willingness-to-pay threshold of £25,000/QALY. When COVID-19 infections were considered, BMS remained dominant and, across 1000 patients, prevented 117 deaths, 124 hospitalizations, and 161 intensive care unit admissions in Group A, and 64 deaths, 65 hospitalizations, and 90 intensive care unit admissions in Group B. Delaying BMS by 5 years resulted in higher costs and lower QALYs in both groups compared with not delaying treatment.

Conclusion

Increased provision of BMS would be expected to reduce COVID-19-related morbidity and mortality, as well as obesity-related co-morbidities, ultimately reducing the clinical and economic burden of obesity.