Genetic Testing for Type 2 Diabetes

Not Applicable

Completed

Interventions: Genetic: genetic testing for type 2 diabetes
Behavioral: Conventional risk counseling
Behavioral: eye disease counseling

Brief Summary: 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: 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.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

Arm && Interventions

Group	Intervention	Description
CR+G	Conventional risk counseling	conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus genetic testing for type 2 diabetes
CR+G	genetic testing for type 2 diabetes	conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus genetic testing for type 2 diabetes
CR+EYE	eye disease counseling	conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus eye disease counseling
CR+EYE	Conventional risk counseling	conventional risk counseling (lifetime risk, fasting plasma glucose, and family history) plus eye disease counseling

Primary Outcome Measures

Name	Time	Method
Weight	3 months	weight 3 months post-enrollment

Secondary Outcome Measures

Name	Time	Method
Daily Caloric Intake	3 months	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
Insulin Resistance (HOMA2-IR)	3 months	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.
Moderate Intensity Physical Activity	3 months	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).
Perceived Lifetime Risk of Type 2 Diabetes	3 months	measured on 1-7 scale (definitely will not get diabetes to definitely will get diabetes)