30% QDiabetes risk = 22% pickup rate for DM in one surgery

One participating surgery has just reported that although only 9 out of 50 people responded to our invite (for those over 30% QDiabetes risk) of those 9 patients, 2 have been shown to have undiagnosed Diabetes, and 4 have borderline HbA1c between 42 and 47.  Thats a 22% pickup rate.  How do we catch the non responders?

So far we are averaging about 14% pickup rate for those responders