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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Surgery for morbid obesity: selection of operation based on evidence from literature review

C Manterola, V Pineda, M Vial, H Losada, and S Munoz.

Review published: 2005.

CRD summary

This review assessed the effects of bariatric surgery for morbid obesity. The authors concluded that the methodological quality of primary studies up to 2002 has been poor. The authors' conclusions are appropriate and warranted given the evidence reviewed.

Authors' objectives

To assess the effects of bariatric surgery for morbid obesity on excess weight loss, surgical failure and reduction of co-morbidities.


MEDLINE, LILACS and the Cochrane Library were searched from January 1990 to December 2002; the search terms were reported. Studies were restricted to those published in Spanish, English, French or Italian.

Study selection

Study designs of evaluations included in the review

Studies of all designs were eligible for inclusion. Review and discussion articles, letters to the editor and clinical guidelines were excluded.

Specific interventions included in the review

Studies that assessed vertical or horizontal gastroplasty, adjusted or non-adjusted gastric banding, gastric bypass, open surgery or laparoscopy were eligible for inclusion. The included studies used laparoscopic and open banding, gastroplasty, gastric bypass and biliopancreatic diversion.

Participants included in the review

Studies that included patients aged older than 19 years with morbid obesity, defined as a body mass index (BMI) of at least 40 kg/m2 or a BMI greater than 35 kg/m2 with co-morbidity, and who had not undergone prior bariatric surgery, were eligible for inclusion.

Outcomes assessed in the review

Studies that assessed weight loss at 12, 24 and 36 months, reduction in co-morbidity, the percentage excess weight loss, operative complications, reoperations, hospital length of stay, follow-up, the percentages of successful and unsuccessful operations, and mortality associated with the operations, were eligible for inclusion.

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Assessment of study quality

The validity of the primary studies was assessed using a scale that assesses study design, sample size and other methodological aspects. The final potential score for each study ranged from 6 to 36 points. Studies scoring 18 points or more were considered higher quality. The authors did not state how many reviewers performed the validity assessment.

Data extraction

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction.

The percentage reductions in BMI (at 12, 24 and 36 months), excess weight loss and co-morbidities were calculated, along with the percentage of patients experiencing morbidity, mortality or reoperation, and the length of hospital stay.

Methods of synthesis

How were the studies combined?

The studies were grouped according to the type of surgery and by outcome measure, and a narrative synthesis was undertaken. The average percentage of patients with outcomes of interest were calculated for open surgery and for laparoscopic surgery. Publication bias was not assessed.

How were differences between studies investigated?

Differences between the studies were discussed according to methodological quality and the type of surgery.

Results of the review

Thirty-one studies involving 37 comparisons were included (n=8,446; 5,216 patients were treated with open surgery and 3,230 with laparoscopic surgery). There were 9 non-randomised or non-blinded clinical trials, 2 retrospective cohort studies and 26 case series.

The median quality score for the studies was 11 (out of a possible range of 6 to 29). When grouped according to therapy, the median quality score was 11 (95% confidence interval, CI: 7.0, 14.1) for studies assessing laparoscopy and 13 (95% CI: 9.0, 17) for studies assessing open surgery techniques.

Operative mortality was 0% for open surgery and 0.4% for laparoscopic surgery. The overall total mortality was 0.3% for open surgery at 35.7 months' follow-up, and 0.4% for laparoscopic surgery at 24.2 months' follow-up. At these same lengths of follow-up, morbidity was 16.7% for open surgery and 14.8% for laparoscopic surgery. The proportion of reoperations was 11.3% with open surgery versus 17.7% with laparoscopic surgery. At 36 months, the percentage reductions in BMI, excess weight loss and co-morbidities for open versus laparoscopic surgery were 30.9% versus 23.7%, 61.9% versus 55.9%, and 74.1% versus 70.9%, respectively. The length of hospital stay was 7 days for open surgery versus 3.8 days for laparoscopic surgery.

Authors' conclusions

The methodological quality of primary studies assessing bariatric surgery up until 2002 has been poor.

CRD commentary

The review objectives were clear, and the review question had been defined in terms of the interventions, participants, outcomes and study designs. A number of databases were searched, but no efforts were made to locate unpublished studies and several publications were not obtained. This means that some relevant studies might have been missed. Efforts were, however, made to minimise language bias. Since it was unclear how many reviewers selected the studies, assessed validity and extracted the data, it is not known whether any efforts were made to minimise reviewer bias and errors in the review process. The quality of the included studies had only been partially assessed, as it was limited to only five methodological aspects of the primary studies.

The use of a narrative synthesis was appropriate given the differences between the studies, and these were discussed in relation to the different procedures and study quality. Overall, the authors' conclusion about the quality of the primary studies is appropriate and warranted given the evidence reviewed.

Implications of the review for practice and research

The authors did not state any implications for practice or further research.

Bibliographic details

Manterola C, Pineda V, Vial M, Losada H, Munoz S. Surgery for morbid obesity: selection of operation based on evidence from literature review. Obesity Surgery 2005; 15(1): 106-113. [PubMed: 15760508]

Indexing Status

Subject indexing assigned by NLM


Body Mass Index; Confidence Intervals; Evidence-Based Medicine; Female; Gastric Bypass /adverse effects /methods; Gastroplasty /adverse effects /methods; Humans; Laparoscopy /adverse effects /methods; Male; Obesity, Morbid /diagnosis /surgery; Patient Satisfaction; Patient Selection; Postoperative Complications /epidemiology; Probability; Prognosis; Risk Assessment; Surgical Procedures, Operative /adverse effects /methods; Treatment Outcome; Weight Loss



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 15760508