Diabetes in adolescents not accurately diagnosed by HbA1c test, study says

July 21, 2011

Glycated hemoglobin (HbA1c) may now be internationally accepted for diagnosing diabetes, but it appears to be far less accurate for adolescents than adults, according to a new study. Read the results and analysis of a recent study here.

Glycated hemoglobin (HbA1c) may now be internationally accepted for diagnosing and monitoring diabetes, but it appears to be far less accurate for use in adolescents than adults, according to a new study.

Researchers caution that more studies are needed until HbA1c can confidently be used to diagnose diabetes and prediabetes in adolescents. Earlier this year, the World Health Organization (WHO) formally accepted the use of HbA1c for the diagnosis of diabetes, calling it a “practical method” that does not always require a patient to fast before a blood sample or to consume an unpalatable glucose drink.

In the study of adolescent diagnosis, patients were defined as having diabetes (fasting plasma glucose [FPG], ≥126 mg/dL; 2-hour plasma glucose [2-hr PG], ≥200 mg/dL) or prediabetes (100 mg/dL ≤ FPG <126 mg/dL; 140 ≤ 2-hr PG <200 mg/dL). Receiver operator character (ROC) analyses were used to evaluate HbA1c test performance.

Researchers reported that in assessing FPG to detect diabetes, an HbA1c of 6.5% had sensitivity rates of 75% (30.1%-95.4%) and 53.8% (47.4%-60%) and specificity rates of 99.9% (99.5%-100%) and 99.5% (99.3%-99.6%) for adolescents and adults, respectively. Additionally, when assessing FPG to detect prediabetes, an HbA1c of 5.7% had sensitivity rates of 5.0% (2.6%-9.2%) and 23.1% (21.3%-25%) and specificity rates of 98.3% (97.2%-98.9%) and 91.1% (90.3%-91.9%) for adolescents and adults, respectively.

According to the investigators, ROC analyses suggested that HbA1c was a poorer predictor of diabetes mellitus (area under the curve [AUC], 0.88 vs 0.93) and prediabetes (FPG AUC, 0.61 vs 0.74) for adolescents compared with adults. Accuracy was no better when 2-hr PG measurements were used, they said.

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