Genetic Testing for Type 2 Diabetes

Study Overview
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Brief Summary
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In this 6-month randomized, controlled trial, we examined whether providing participants with genetic test results and counseling regarding their risk for type 2 diabetes would motivate them to improve their health behaviors and lose weight to reduce their diabetes risk. We hypothesized that participants who received conventional diabetes counseling plus genetic test results and counseling would have at least 6 lb greater weight loss at 3 months than participants who received conventional diabetes counseling without genetic test results.

Detailed Description
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In this 6-month randomized, controlled trial, we evaluated the impact of genetic testing for type 2 diabetes on psychological, health behavior, and clinical outcomes. Eligibility criteria included age 21 to 65 years, overweight or obese (body mass index [BMI] >27 kg/m2), and no prior diagnosis of type 2 diabetes. At baseline, participants (N=601) had conventional risk factors assessed, including demographics, fasting plasma glucose (FPG), and family history. They also provided blood samples for genetic testing of TCF7L2, PPARG, and KCNJ11, three genes that confer elevated risk for development of type 2 diabetes. Participants were then randomized to receive conventional counseling plus control eye disease counseling (CR+EYE) or conventional counseling plus genetic test results (CR+G). Two to four weeks following the baseline visit, when the genetic test results were available, participants returned for a visit with a genetic counselor. All participants received conventional risk counseling based on their lifetime population risk, FPG results, and family history. Next, participants were informed of their randomization assignments; CR+EYE participants received counseling on eye diseases, whereas CR+G participants received genetic counseling. Then perceived risk, affect, self-efficacy, and readiness to change were assessed. All other outcomes were also assessed at 3 and 6 months.

Official Title
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The Impact of Genetic Testing for Type 2 Diabetes on Health Behaviors

Conditions
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Diabetes Mellitus

Intervention / Treatment
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* Genetic: genetic testing for type 2 diabetes
* Behavioral: Conventional risk counseling
* Behavioral: eye disease counseling


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: body mass index >27 kg/m2 baseline fasting plasma glucose <=125 mg/dL Exclusion Criteria: prior diagnosis of type 2 diabetes fasting plasma glucose >125 mg/dL on more than one occasion HbA1c > 7% taking diabetes medication actively losing weight enrolled in research study focusing on lifestyle changes unable to provide informed consent or answer survey questions unassisted residing in nursing home or receiving home health care active diagnosis of psychosis or dementia at least one error on 6-item cognitive screener

Ages Eligible for Study
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Minimum Age: 21 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: CR+G<br>conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus genetic testing for type 2 diabetes | Genetic: genetic testing for type 2 diabetes<br>* TCF7L2, PPARG, or KCNJ11<br>Behavioral: Conventional risk counseling<br>* Risk based on lifetime risk, fasting plasma glucose results, and family history.<br>|
| Active Comparator: CR+EYE<br>conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus eye disease counseling | Behavioral: Conventional risk counseling<br>* Risk based on lifetime risk, fasting plasma glucose results, and family history.<br>Behavioral: eye disease counseling<br>* addresses risk for age-related macular degeneration, glaucoma, cataracts<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Weight | weight 3 months post-enrollment | 3 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Insulin Resistance (HOMA2-IR) | Calculated using the updated homeostasis model assessment (HOMA) calculator at http://www.dtu.ox.ac.uk/homacalculator/ Higher numbers indicate higher insulin resistance. There are no established cutoffs indicating impaired resistance. | 3 months | 
| Perceived Lifetime Risk of Type 2 Diabetes | measured on 1-7 scale (definitely will not get diabetes to definitely will get diabetes) | 3 months | 
| Daily Caloric Intake | Estimated daily caloric intake based on self-reported frequency and amount of intake of specific foods over the past 3 months as assessed by the Block Brief Food Frequency Questionnaire | 3 months | 
| Moderate Intensity Physical Activity | self-report based on the long version of the International Physical Activity Questionnaire. Moderate physical activity was queried in the domains of work (e.g., carrying light loads), transportation (e.g., bicycling), domestic chores and gardening (e.g., sweeping, raking), and leisure-time (e.g., bicycling, swimming). | 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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genetic screening