Identifying adolescents with high fasting glucose: the importance of adding grandparents' data when assessing family history of diabetes

Abstract

Objective: To evaluate the role of adding grandparents' data to parental information to the assessment of a family history of diabetes, in order to identify adolescents with high fasting glucose. Method: In 2003 we evaluated 1276 population-based 13-year-olds, from Porto, Portugal. The history of diabetes in parents and grandparents was collected using self-reported questionnaires and a clinical evaluation was performed, including a fasting blood sample. The 75th percentile of fasting plasma glucose (FPG = 91 mg/dl) was used to create two groups of participants (high vs. low fasting glucose). Results: No association was found between family history of diabetes (with or without grandparental data) and a high FPG. The sensitivity to identify individuals with high FPG increased from 7.8% to 47.9% when grandparental history was combined with parental data. The positive predictive value was slightly increased (25.2% vs. 27.8%) but the specificity dropped (91.8% vs. 56.4%). Conclusion: Combining parental with grandparental history increased the number of adolescents with a positive family history of diabetes and also increased the sensitivity to identify adolescents with high FPG. So, even if it determines a decrease in specificity, grandparental data is relevant when screening for high fasting glucose in adolescents.