Non-invasive type 2 diabetes risk scores do not identify diabetes when the cause is β-cell failure: The Africans in America study

Background: Emerging data suggests that in sub-Saharan Africa beta-cell-failure in the absence of obesity is a frequent cause of type 2 diabetes (diabetes). Traditional diabetes risk scores assume that obesity-linked insulin resistance is the primary cause of diabetes. Hence, it is unknown whether diabetes risk scores detect undiagnosed diabetes when the cause is beta-cell-failure. Aims: In 528 African-born Blacks living in the United States [age 38 +/- 10 (Mean +/- SE); 64% male; BMI 28 +/- 5 kg/m(2)] we determined the: (1) prevalence of previously undiagnosed diabetes, (2) prevalence of diabetes due to beta-cell-failure vs. insulin resistance; and (3) the ability of six diabetes risk scores [Cambridge, Finnish Diabetes Risk Score (FINDRISC), Kuwaiti, Omani, Rotterdam, and SUNSET] to detect previously undiagnosed diabetes due to either beta-cell-failure or insulin resistance. Methods: Diabetes was diagnosed by glucose criteria of the OGTT and/or HbA1c >= 6.5%. Insulin resistance was defined by the lowest quartile of the Matsuda index (<= 2.04). Diabetes due to beta-cell-failure required diagnosis of diabetes in the absence of insulin resistance. Demographics, body mass index (BMI), waist circumference, visceral adipose tissue (VAT), family medical history, smoking status, blood pressure, antihypertensive medication, and blood lipid profiles were obtained. Area under the Receiver Operator Characteristics Curve (AROC) estimated sensitivity and specificity of each continuous score. AROC criteria were: Outstanding: >0.90; Excellent: 0.80-0.89; Acceptable: 0.70-0.79; Poor: 0.50-0.69; and No Discrimination: 0.50. Results: Prevalence of diabetes was 9% (46/528). Of the diabetes cases, beta-cell-failure occurred in 43% (20/46) and insulin resistance in 57% (26/46). The beta-cell-failure group had lower BMI (27 +/- 4 vs. 31 +/- 5 kg/m(2) P < 0.001), lower waist circumference (91 +/- 10 vs. 101 +/- 10cm P < 0.001) and lower VAT (119 +/- 65 vs. 183 +/- 63 cm(3), P < 0.001). Scores had indiscriminate or poor detection of diabetes due to beta-cell-failure (FINDRISC AROC = 0.49 to Cambridge AROC = 0.62). Scores showed poor to excellent detection of diabetes due to insulin resistance, (Cambridge AROC = 0.69, to Kuwaiti AROC = 0.81). Conclusions: At a prevalence of 43%, beta-cell-failure accounted for nearly half of the cases of diabetes. All six diabetes risk scores failed to detect previously undiagnosed diabetes due to beta-cell-failure while effectively identifying diabetes when the etiology was insulin resistance. Diabetes risk scores which correctly classify diabetes due to beta-cell-failure are urgently needed.

Automated summary

This study found that beta-cell-failure is a frequent cause of type 2 diabetes in sub-Saharan Africa. Traditional diabetes risk scores are unable to detect diabetes caused by beta-cell-failure, but they are effective in identifying diabetes caused by insulin resistance.