Ruth Cassidy

Effect of registration on cyclical kinematic data.

Given growing interest in functional data analysis (FDA) as a useful method for analyzing human movement data, it is critical to understand the effects of standard FDA procedures, including registration, on biomechanical analyses. Registration is used to reduce phase variability between curves while preserving the individual curves shape and amplitude. The application of three methods available to assess registration could benefit those in the biomechanics community using FDA techniques: comparison of mean curves, comparison of average RMS values, and assessment of time-warping functions. Therefore, the present study has two purposes. First, the necessity of registration applied to cyclical data after time normalization is assessed. Second, we illustrate the three methods for evaluating registration effects. Masticatory jaw movements of 22 healthy adults (2 males, 21 females) were tracked while subjects chewed a gum-based pellet for 20s. Motion data were captured at 60 Hz with two gen-locked video cameras. Individual chewing cycles were time normalized and then transformed into functional observations. Registration did not affect mean curves and warping functions were linear. Although registration decreased the RMS, indicating a decrease in inter-subject variability, the difference was not statistically significant. Together these results indicate that registration may not always be necessary for cyclical chewing data. An important contribution of this paper is the illustration of three methods for evaluating registration that are easy to apply and useful for judging whether the extra data manipulation is necessary.

Technique or technology? Evaluating leaks after gastric bypass

OBJECTIVE To assess the relationship between technique and surgical devices on anastomotic and staple-line leaks after laparoscopic Roux-en-Y gastric bypass. BACKGROUND Leaks after bariatric surgery remain a major source of morbidity and mortality. The association of surgical technique and devices with leaks after gastric bypass is poorly understood. SETTING Multi-centered study that included teaching and non-teaching hospitals that participate in a statewide consortium for quality improvement using a payer-funded outcome registry. METHODS We analyzed data from the Michigan Bariatric Surgery Collaborative and performed a case-control study comparing patients who sustained a leak with those who did not after primary laparoscopic Roux-en-Y gastric bypass. A total of 71 (.44%) patients with leaks were identified between January 2007 and December 2011. The leak group was matched 1:2 to a control group (nonleak) based on procedure type, age, body mass index, sex, and the year in which the procedure was performed. Technique-specific case characteristics and device-specific factors were assessed by reviewing operative notes from all primary bariatric procedures in our study population. RESULTS The rate of leak decreased during the study period, and there was a significant downward trend (slope estimate: -.19961%, P = .0372). After performing multivariate analysis, the type of anastomosis (circular stapler, hand-sewn, or linear stapler) and stapler manufacturer were not associated with leaks. The use of buttressing material was associated with a higher rate of leaks (odds ratio: 8.79 [95% confidence interval: 2.49-31.01], P = .0007), whereas the use of fibrin sealant was associated with a lower rate of leaks (odds ratio .11 [95% confidence interval: .03-.41], P = .0013). These findings could not be explained by differences in measures of surgeon performance. CONCLUSION Leak rates after laparoscopic gastric bypass have fallen in Michigan despite variations in technique and device utilization. Although the type of anastomosis and stapler manufacturer do not appear to be significantly associated with leaks, it appears that the use of buttressing material was more common in cases in which leaks occurred, whereas the use of fibrin sealant was not. Given the complex interplay of multiple variables that affect surgical outcomes, future studies justifying the benefits of operative devices should be evaluated prospectively in the context of surgeon technique and skill.

Evaluating the effect of operative technique on leaks after laparoscopic sleeve gastrectomy: a case-control study ☆

OBJECTIVE To assess the effect of operative technique on staple line leaks after laparoscopic sleeve gastrectomy (LSG). BACKGROUND Staple-line leaks after LSG are a major source of morbidity and mortality. Variations in operative technique exist; however, their effect on leaks is poorly understood. METHODS We analyzed data from the Michigan Bariatric Surgery Collaborative (MBSC) to perform a case-control study comparing patients who had a clinically significant leak after undergoing a primary LSG to those who did not. A total of 45 patients with leaks were identified between January 2007 and December 2013. The leak group was matched 1:2 to a control group based on procedure type, age, body mass index, sex, and year the procedure was performed. Technique-specific factors were assessed by reviewing operative notes from all primary bariatric procedures in our study population. Conditional logistic regression was used to identify techniques associated with leaks. To increase the power of our analysis, we used a significance level of .10. RESULTS Leak rates with LSG have decreased over the past 5 years (1.18% to .36%) as annual case volume has increased (846 cases/yr to 4435 cases/yr). Surgeons who performed 43 or more cases per year had a leak rate<1%. Leaks were more common among cases requiring a blood transfusion (26.2% versus 1.08%, P = .0031) and when cases were converted to open surgery (7.14% versus 0%, P = .0741). However, there was no significant difference in operative time between cases involving a leak and their matched controls (95.4 min versus 87.1 min, P = .1197). Oversewing of the staple line was the only technique associated with less leaks after controlling for confounding factors (OR .397 CI .174, .909, P = .0665). Notably, surgeons who oversewed routinely were also found to have higher case volume (307 versus 140, P = .0216) and less overall complication rates (4.81% versus 7.95%, P = .0027). Furthermore, oversewing technique varied widely as only 22.6% of cases involved oversewing of the entire staple line. CONCLUSION Despite considerable variation in operative technique, leak rates with laparoscopic sleeve gastrectomy have decreased over time as operative volume has increased. Oversewing of the staple line was associated with fewer leaks, but specific suturing technique was not uniform and oversewing was performed routinely by more experienced surgeons with higher case volumes and less complication rates overall. Before standardizing surgical technique one must take into account variations in surgeon skill and experience.

Factors Associated With Achieving a Body Mass Index of Less Than 30 After Bariatric Surgery

Importance Achieving a body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) of less than 30 is an important goal of bariatric surgery, given the increased risk for weight-related morbidity and mortality with a BMI above this threshold. Objective To identify predictors for achieving a BMI of less than 30 after bariatric surgery. Design, Setting, and Participants This retrospective study used data from the Michigan Bariatric Surgery Collaborative, a statewide quality improvement collaborative that uses a prospectively gathered clinical data registry. A total of 27 320 adults undergoing primary bariatric surgery between June 2006 and May 2015 at teaching and nonteaching hospitals in Michigan were included. Exposure Bariatric surgery. Main Outcomes and Measures Logistic regression was used to identify predictors for achieving a BMI of less than 30 at 1 year after surgery. Secondary outcome measures included 30-day postoperative complications and 1-year self-reported comorbidity remission. Results A total of 9713 patients (36%; mean [SD] age, 46.9 [11.3] years; 16.6% male) achieved a BMI of less than 30 at 1 year after bariatric surgery. A significant predictor for achieving this goal was a preoperative BMI of less than 40 (odds ratio [OR], 12.88; 95% CI, 11.71-14.16; P < .001). Patients who had a sleeve gastrectomy, gastric bypass, or duodenal switch were more likely to achieve a BMI of less than 30 compared with those who underwent adjustable gastric banding (OR, 8.37 [95% CI, 7.44-9.43]; OR, 21.43 [95% CI, 18.98-24.19]; and OR, 82.93 [95% CI, 59.78-115.03], respectively; P < .001). Only 8.5% of patients with a BMI greater than 50 achieved a BMI of less than 30 after bariatric surgery. Patients who achieved a BMI of less than 30 had significantly higher reported rates of medication discontinuation for hyperlipidemia (60.7% vs 43.2%, P < .001), diabetes (insulin: 67.7% vs 50.0%, P < .001; oral medications: 78.5% vs 64.3%, P < .001), and hypertension (54.7% vs 34.6%, P < .001), as well as a significantly higher rate of sleep apnea remission (72.5% vs 49.3%, P < .001) and higher satisfaction rate (92.8% vs 78.0%, P < .001) compared with patients who did not. Conclusions and Relevance Patients with a preoperative BMI of less than 40 are more likely to achieve a BMI of less than 30 after bariatric surgery and are more likely to experience comorbidity remission. Policies and practice patterns that delay bariatric surgery until the BMI is 50 or greater can result in significantly inferior outcomes.

Are Patient-reported Outcomes Correlated With Clinical Outcomes After Surgery?: A Population-based Study.

Objective: To evaluate the extent to which patient-reported outcomes (PROs) (eg, health-related quality of life) are distinct from clinical outcomes following bariatric surgery. Background: Hospital quality measurement often focuses on traditional clinical outcomes (eg, complications). However, PROs may provide a unique perspective regarding performance, particularly for common, low-risk procedures. Methods: We used data from 11,420 patients who underwent bariatric surgery (2008–2012) from the Michigan Bariatric Surgery Collaborative (39 hospitals). We included both short-term (30-day complication rates) and long-term (1-year weight loss and comorbidity resolution) outcomes. For PROs, we used health-related quality of life assessed by the Health and Activities Limitations Index (HALex) and Bariatric Quality of Life (BQL) index preoperatively and at 1 year. We used multivariable linear regression to determine the association between these PROs and both short and long-term clinical outcomes, adjusting for patient factors and the type of surgical procedure. Results: After adjustment for risk factors and surgical procedure, hospital rankings based on PROs (either the average change in HALex or BQL scores) were not correlated with hospital rankings based on complications. In contrast, both PRO measures were correlated with weight loss. Specifically, the average change in HALex score (R2 = 0.24, P < 0.002) and average change in BQL score (R2 = 0.44, P < 0.001) were correlated with hospital average percent excess. One PRO measure—BQL score—was correlated with a decline in the need for medications due to associated comorbidities (R2 = 0.16, P < 0.01). After accounting for short and long-term clinical outcomes, between 15% and 44% of the variation in PROs remained unexplained at the hospital level. Conclusions: Patient-reported outcomes are not correlated with early perioperative events, but are correlated with measures of clinical effectiveness after bariatric surgery. A comprehensive approach to surgical quality should incorporate both clinical events and self-reported measures of health status throughout the short and long-term recovery period.

Variation in Patient-reported Outcomes Across Hospitals Following Surgery.

Background:Although there is growing interest in applying patient-reported outcomes (PROs) toward surgical quality, the extent to which PROs vary across hospitals following surgical procedures is unknown. Objectives:We examined variation in PROs, specifically health-related quality of life (HRQOL), across hospitals performing bariatric surgery. Research Design:A retrospective cohort study. Subjects:The Michigan Bariatric Surgery Collaborative is a statewide consortium of 39 hospitals performing laparoscopic gastric bypass, gastric banding, or sleeve gastrectomy (n=11,420 patients between 2008 and 2012). Measures:We examined generic and disease-specific HRQOL measured by the Health and Activities Limitations Index (HALex) and Bariatric Quality of Life index (BQL) preoperatively and at 1 year. We measured the variation in postoperative HRQOL across hospitals, and the effect of risk and reliability adjustment on hospital ranking. Results:In this cohort, HRQOL varied by 56% (HALex) and 37% (BQL) across hospitals. Patient factors accounted for 58% (HALex) to 71% (BQL) of the variation in HRQOL across hospitals. After risk and reliability adjustment, HRQOL varied by 18% (by HALex) and 14.5% (by BQL) across hospitals, and the proportion of patients who experienced a large improvement in HRQOL by HALex ranged from 33% to 69% and 67% to 92% by BQL. After adjusting for patient factors and reliability, these differences diminished to 55%–64% (HALex) and 79%–84% (BQL). Conclusions:Patient factors explain a large proportion of hospital-level variation in PROs following bariatric surgery, underscoring the importance of risk adjustment. However, some variation in PROs across hospitals remains unexplained, suggesting PROs may represent a viable indicator of hospital performance.

Clinical versus patient-reported measures of depression in bariatric surgery

BackgroundBariatric surgery patients with mental illness may experience worse surgical outcomes compared to those without. Depression is the most prevalent mental health diagnosis amongst Americans with obesity. Accurate diagnosis and treatment is of paramount importance to mitigate perioperative risk. Unfortunately, there is no standard method to screen patients for depression prior to surgery. Our goal was to understand the relationship between traditional clinical screening tools and a novel patient-reported depression screening survey, Patient Health Questionnaire 8 (PHQ-8), in the setting of the bariatric surgery preoperative assessment.MethodsThe study included all adult bariatric surgery patients from January 2014 through June 2016. Patients who were not assessed using both the PHQ-8 and a traditional clinical depression screening were excluded from the study. There were a total of 4486 patients who met the eligibility criteria and were included in analysis. We used comparative statistics to examine the association between these screening tools and to test for contributing demographic, surgical, and socioeconomic factors.ResultsThe overall rate of clinically diagnosed depression in the study cohort was 45.6%. In comparison, 14.8% of all patients screened positive for depression using the PHQ-8. Of the patients without a traditional clinical diagnosis of depression, 10.2% screened positive for depression using the PHQ-8. This subset of undiagnosed patients was more likely to be non-white, employed, and had a higher BMI than their clinically diagnosed counterparts.Conclusions and RelevanceWe found a higher rate of clinically diagnosed depression in our cohort compared to the general population. However, when using the validated PHQ-8 survey, the rate of depression more closely approximated the national incidence. Further, a significant proportion of patients were undiagnosed and/or misdiagnosed by current clinical assessments. Standardizing preoperative depression screening using validated patient-centered tools may prevent the consequences of untreated depression.