Systematic review of risk prediction models for diabetes after bariatric surgery

BACKGROUND

Diabetes remission is an important outcome after bariatric surgery. The purpose of this study was to identify risk prediction models of diabetes remission after bariatric surgery.

METHODS

A systematic literature review was performed in MEDLINE, MEDLINE-In-Process, Embase and the Cochrane Central Register of Controlled Trials databases in April 2015. All English-language full-text published derivation and validation studies for risk prediction models on diabetic outcomes after bariatric surgery were included. Data extraction included population, outcomes, variables, intervention, model discrimination and calibration.

RESULTS

Of 2330 studies retrieved, eight met the inclusion criteria. Of these, six presented development of risk prediction models and two reported validation of existing models. All included models were developed to predict diabetes remission. Internal validation using tenfold validation was reported for one model. Two models (ABCD score and DiaRem score) had external validation using independent patient cohorts with diabetes remission assessed at 12 and 14 months respectively. Of the 11 cohorts included in the eight studies, calibration was not reported in any cohort, and discrimination was reported in two.

CONCLUSION

A variety of models are available for predicting risk of diabetes following bariatric surgery, but only two have undergone external validation.

Pregnancy after diabetes obesity surgery (PADOS): Qualitative study of pre-pregnancy care

Half of all bariatric surgical procedures are in women of childbearing age. Surgery may improve fertility yet exacerbate nutritional deficiencies, that may be disadvantageous to the fetus. A frequently encountered subgroup of obese women have type 2 diabetes. The health risks, to both mother and child, of diabetes in pregnancy are well described including 4.7× risk of stillbirth and 2× risk of congenital abnormality. What is not clear is whether bariatric surgery mitigates or complicates the health consequences of women with obesity and diabetes in pregnancy. In addition the influence of the type of surgery, the optimal interval between surgery and conception and evidence based preconception recommendations are unknown. This study complements wider research aiming to inform optimal management of this patient population. Obese diabetic women require clear guidance regarding pregnancy planning after surgery. This study will develop an understanding of the barriers and facilitators (psychological, behavioural, attitudinal and nutritional) to achieving effective pre-pregnancy health and care in women with type 2 diabetes who have undergone metabolic surgery. Currently women's perception of fertility issues and risks after bariatric surgery is unknown and thus a qualitative interpretive paradigm was chosen. Interviews with the target population will explore decision-making processes; experience regarding metabolic surgery and perceived pregnancy risk. Interviews with a broad range of health professionals involved in bariatric care will include rationale for selected surgical procedure and post surgery referral processes e.g. contraceptive care. This will advance understanding of how to provide targeted support and monitoring.

Pregnancy after diabetes obesity surgery (PADOS): Incidence and outcomes

Half of all bariatric surgical procedures are in women of childbearing age but it remains unclear whether surgery is suitable for women who subsequently conceive: specifically the relative risks and benefits of potential nutrient deficiencies versus weight reduction. We will present data collected from Clinical Practice Research Databases on the maternal and fetal outcomes of pregnancies complicated either by obesity or previous bariatric surgery (BS). Two groups, matched to obese controls for BMI pre-BS and post-BS (at the time of ante-natal booking) will be compared. In this way, the effect of BS on pregnancy outcomes may be examined, independent of its effect on weight. A sub-group of women with antecedent Type 2 diabetes (T2DM) will allow for investigation of the additional impact and persistence of this co-morbidity. This builds upon pilot data collected from a retrospective cohort of women (18-45years) undergoing laparoscopic roux-en-Y (RYGB) surgery over a 24-month period (n=218). After exclusions and loss to follow up, data from 111 patients were analysed; 81 (73%) had conceived prior to RYGB, 20 (18%) became pregnant post RYGB and a further 22 patients (20%) were trying to conceive at the time of data collection. Three women had T2DM which resolved post BS. A suggestion of greater miscarriage risk prior to surgery in this sub-group will be confirmed as more women are recruited. Pregnancy is a frequent desire/occurrence after BS. This database study will advance understanding of the maternal and fetal outcomes of such pregnancies and inform antenatal care.

Letter 1: randomized clinical trial of bowel preparation with a single phosphate enema or polyethylene glycol before elective colorectal surgery (Br J Surg 2006; 93: 427-433)

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