I don't trust those "pop-up" clinics that test for pre-diabetes, either. Two people who are close to me submitted samples at health fairs. They were both told that they were pre-diabetic (although follow-up with their own primary care showed no such thing). Then, they both got notices from their health insurers that their rates may be raised due to a diagnosis of pre-diabetes. They had to have their primary physicians submit data to show that they did not have this condition. If you need to test for a health condition, do so through your own physician.