Genetic Testing for Type 2 Diabetes

Background:

T2DM is a debilitating, deadly, and costly chronic disease whose prevalence is increasing.
Although the development of T2DM can be delayed or prevented by lifestyle changes, changes
initiated too late may not delay T2DM onset indefinitely. Therefore, it is imperative to
intervene earlier and to find new ways to increase motivation to initiate and maintain
lifestyle changes.

Objectives:

New approaches to primary prevention could incorporate tests for genetic and genomic risk of
T2DM, creating a sizable and growing opportunity for the translation of such tests into
primary care and public health practice. However, the ability for these tests to demonstrate
improvement in patients' health outcomes remains unknown, posing a major obstacle to further
translation. In this 6-month randomized, controlled trial, we will evaluate the impact of
genetic testing for T2DM on psychological, health behavior, and clinical outcomes.

Methods:

Eligibility criteria include age 21 to 65 years, overweight or obese (body mass index [BMI]
>27 kg/m2), and no prior diagnosis of T2DM. At baseline, participants (N=600) will have
conventional risk factors assessed, including demographics, fasting plasma glucose (FPG),
and family history. They will also provide cheek tissue samples for genetic testing of
TCF7L2, PPARG, and KCNJ11, three genes that confer elevated risk for development of T2DM.
Participants will then be randomized to receive conventional counseling only (CR) or
conventional counseling plus genetic test results (CR+G). One to two weeks following the
baseline visit, when the genetic test results are available, participants will return for a
visit with a genetic counselor. All participants will receive conventional risk counseling
based on their lifetime population risk, FPG results, and family history. Next, participants
will be informed of their randomization assignments; CR participants will receive general
health risk counseling on issues unrelated to T2DM, whereas CR+G participants will receive
genetic counseling. Then perceived risk, affect, self-efficacy, and readiness to change will
be assessed. All other outcomes will be assessed at 3 and 6 months.

Status:

Enrollment for the RCT phase of this project began in January 2011 and is ongoing.
Currently, there are 323 participants enrolled.

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