A group of researchers led by Dr Diane Becker of the Johns Hopkins Medical Institutions in Baltimore, USA, evaluated the risk of developing diabetes in members of high-risk families with fasting plasma glucose (FPG) concentrations within the normal range. A total of 542 non-diabetic adults aged 30-59 with siblings with documented premature coronary disease were followed prospectively to determine the incidence of type 2 diabetes. The mean follow-up was 8.7 years.

The researchers found that 45 patients (7.8%) developed type 2 diabetes during the follow-up period. The incidence of diabetes increased with increasing thresholds of FPG (5.0, 5.6, 6.1, and 6.7mmol/L; p for trend <0.0001). The multivariable adjusted relative risk of developing diabetes in patients with FPG 5.0mmol/L or more, compared with those with FPG <5.0mmol/L, was 14.9 (95% CI 3.4-65.2). All FPG thresholds within the normal range (5.0 and 5.6mmol/L) had diagnostic efficiency levels >0.74, and maximal diagnostic efficiency for FPG was achieved at 5.50mmol/L, which had a sensitivity and specificity of 0.782.

The researchers concluded that higher FPG concentrations within the normal range were an independent risk factor for type 2 diabetes in high-risk adults, and may help identify candidates for primary preventive interventions.

Diabetes Research and Clinical Practice 2006;74:267-73