CRD summary

This review concluded that there was preliminary evidence to support continued investigation of surgery as a means of achieving lasting resolution of type 2 diabetes in the non-morbidly obese population. Numerous shortcomings in the review process mean that these conclusions should be treated with caution.

Authors' objectives

To assess bariatric surgery in patients with a body mass index (BMI) less than 35kg/m² for the resolution of type 2 diabetes.

Searching

MEDLINE, Current Contents, Science Citation Index and The Cochrane Library were searched from January 1979 to October 2009. Search terms were reported. References of identified studies were checked. Only studies published in English in peer reviewed journals were eligible for inclusion.

Study selection

Studies that provided data on the treatment of type 2 diabetes using any form of metabolic/bariatric surgery in which mean BMI was less than 35kg/m² were eligible for inclusion.

Included studies assessed the following restrictive, malabsorptive/restrictive or malabsorptive procedures: biliopancreatic diversion (BPD), stomach- and pylorus-preserving BPD (BPD-SPP), Roux-en-Y gastric bypass (RYGB), laparoscopic adjustable gastric banding (LAGB), duodenal-jejunal bypass (DJB), mini-gastric bypass (MGB), ileal interposition with sleeve gastrectomy (IL-SG) and ileal interposition with diverted sleeve gastrectomy (IL-DSG). Various definitions of type 2 diabetes resolution were employed. Outcomes assessed were BMI, fasting plasma glucose, haemoglobin A1C (HbA_1c), diabetes medication usage and safety. Sixty-six per cent of patients in the included studies were female. Mean age ranged from 38.2 to 56 years. Most patients were diagnosed with type 2 diabetes within one to 10 years of surgery. Most patients took a daily for of oral or injectable diabetes medication. Mean baseline BMI was 29.4kg/m². Mean baseline fasting plasma glucose was 198.5mg/dL. Mean baseline glycated HbA_1c was 8.7%.

The authors did not state how many reviewers performed the study selection.

Assessment of study quality

The authors did not state that they assessed validity.

Data extraction

Baseline pre-operative and postoperative follow-up data were extracted for all outcomes.

The authors did not state how many reviewers performed the data extraction.

Methods of synthesis

Pre-operative and postoperative weighted means and simple means of means, together with 95% CI, were calculated for pre- and post-operative BMI, fasting plasma glucose and HbA_1c and used to calculate pre-operative to postoperative weighted mean differences and changes in simple means. The combined numbers and percentages of patients off diabetes medication were calculated. Subgroup analyses were carried out for the different types of procedure and status of overweight versus obese. Safety outcomes were summarised narratively.

Results of the review

Sixteen studies (343 participants) were included in the review. Follow-up ranged from six to 216 months. Eleven studies had a prospective design.

Postoperative weighted mean BMI was 24.2kg/m², a weighted mean change of -5.1kg/m² (95% CI -5.3 to -4.8). Postoperative fasting plasma glucose was 105.2mg/dL, a change of -93.3 (95% CI -96.3 to -90.0). HbA1c was 6.0%, a decrease of 2.7% (95% CI -2.8 to -2.6). Resolution of diabetes was experienced by 85.3% of patients (using a definition of HbA1c≤6% and termination of diabetes medications). There was a trend toward resolution with other definitions of diabetes resolution.

One patient died (mortality rate 0.29%). The rate of total complications was 4%.

Results of subgroup analyses for different procedure types were reported.

Authors' conclusions

There was preliminary evidence to support continued investigation of surgery as a possible method of achieving lasting resolution of type 2 diabetes in the non-morbidly obese population.

CRD commentary

The review question and inclusion criteria were clear. Three relevant databases were searched, but the decision to limit the review to peer-reviewed studies published in English increased the chances of selection biases and omission of relevant studies. The authors did not report that they used methods designed to reduce reviewer bias and error at any stage of the review process. No assessment of the validity of the included studies was reported; this made it difficult to determine the strength of the evidence represented in the review. No studies were randomised and most were not controlled. Few details of the statistical synthesis were reported. There was no reported assessment or exploration of statistical heterogeneity between studies.

The authors' conclusions were relatively cautious and were supported by the results reported in the review, but numerous shortcomings in the review process mean that they should be treated with caution.

Implications of the review for practice and research

Practice: The authors did not state any implications for practice.

Research: The authors stated that future trials of bariatric surgery for type 2 diabetes should employ standardised end points. They stated a need for trials to compare surgery with standard medical treatment and identified two such RCTs as being underway.

Funding

Ethicon Eno-Surgery (Europe) GmbH.

Bibliographic details

Fried M, Ribaric G, Buchwald JN, Svacina S, Dolezalova K, Scopinaro N. Metabolic surgery for the treatment of type 2 diabetes in patients with BMI <35 kg/m^2: an integrative review of early studies. Obesity Surgery 2010; 20(6): 776-790. [PubMed: 20333558]

Original Paper URL

http://www.springerlink.com/content/f38121141083l777/

Indexing Status

Subject indexing assigned by NLM

MeSH

Bariatric Surgery /methods; Biliopancreatic Diversion /methods; Blood Glucose /analysis; Body Mass Index; Diabetes Mellitus, Type 2 /drug therapy /metabolism /surgery; Gastrectomy /methods; Gastric Bypass /methods; Gastroplasty /methods; Hemoglobin A, Glycosylated /analysis; Humans; Hypoglycemic Agents /therapeutic use

AccessionNumber

12010007924

Database entry date

12/10/2011

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.