EAL

NCBS: Weight Loss and Weight Regain Expected After Procedure (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To discover the reasons patients do not return for annual follow-up visits and are lost to follow-up after one year
To determine whether long-term follow-up care after RYGBP surgery is a factor in weight loss.

Inclusion Criteria:

Patients who had undergone RYGBP surgery at least three years earlier.

Exclusion Criteria:

Patients who were less than three years post-operative for RYGBP surgery.

Description of Study Protocol:

Recruitment

Subjects recruited from patients of University of Washington Health Bariatric Surgery program.

Design

Retrospective cohort.

Blinding Used

None.

Intervention

Patients who had been lost to follow-up for more than two years were contacted and asked to come into clinic for a follow-up visit. If patients were unable, data were collected by phone.
After data were collected, investigators retrospectively reviewed data and divided post-operative patients into three cohorts according to follow-up status.

Statistical Analysis

Wilcoxon Rank-Sum test
Data presented as mean ± standard deviation of the mean.

Data Collection Summary:

Timing of Measurements

Follow-up visit (two and six weeks, six months and annually) in the three to four years after surgery.

Dependent Variables

Weight loss [percentage of excess weight lost (EWL)]
Distance in miles from patient’s home to surgery center
Initial body mass index (kg per m²)
Age at surgery
Gender.

Independent Variables

RYGBP surgery (three to four years prior to retrospective analysis).

Control Variables

Routine follow-up care offered to all patients.

Description of Actual Data Sample:

Initial N: 85
- Of 103 patients who were eligible (had surgery prior to 2003), 85 were successfully contacted and were retrospectively entered into the study and categorized into one of three cohorts:
  - Cohort 1: N=34 (of 103 who had attended every scheduled follow-up visit)
  - Cohort 2: N=41 (of 51 who had attended every follow-up visit up to and including the first annual visit)
  - Cohort 3: N=10.
Attrition: N=85 (no attrition in retrospective analysis of data)
Mean age: 44 years (range 32 to 57)
Ethnicity: Not described
Anthropometrics: No significant differences in patient anthropometrics at baseline (mean BMI 50kg per m²)
Location: Wisconsin.

Summary of Results:

Variables	Cohort 1 (Attended every F/U visit)	Cohort 2 (Attended every scheduled F/U visit through end of year 1)	Cohort 3 (Lost to F/U prior to first annual visit)	P-Value
Average Interval Between Surgery and Most Recent Encounter (Months)	37±2.0	39±4.0	37±3.0	P>0.05
Excess Weight Loss (%) at 1 Year	70%	65%	N/A	P>0.05
Excess Weight Loss (%) at 2 Years	74%^a	61%^b	60%^b	P<0.05 between ^a and ^b
Distance (Miles)	35±40	43±54	49±49	P>0.05

Author Conclusion:

Laparoscopic bypass patients who attended all follow-up visits lost more weight.

Funding Source:

University/Hospital:

University of Wisconsin School of Medicine

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	Yes
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	Yes
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes