Racial differences in performance of HbA_1c for the classification of diabetes and prediabetes among US adults of non‐Hispanic black and white race

Abstract

Aim To characterize differences between black and white people in optimal HbA 1c thresholds for diagnoses of diabetes and prediabetes.Methods Data were included from the National Health and Nutrition Examination Survey, 2005-2014. Black and white adults (age 18-70 years) who underwent an oral glucose tolerance test and had available fasting plasma glucose, 2h plasma glucose and HbA 1c measurements were eligible for inclusion. Diabetes or prediabetes status was defined by fasting plasma glucose and 2-h plasma glucose using American Diabetes Association criteria. Classification of diabetes, prediabetes and dysglycaemia by HbA 1c was evaluated for a range of HbA 1c thresholds, with optimal thresholds defined as those values that maximized the sum of sensitivity and specificity (Youden's index). ResultsIn 5324 black (32.3%) and white (67.7%) individuals, Youden's index (optimal) thresholds for HbA 1c were ≥42 mmol/mol (6.0%) and ≥39 mmol/mol (5.7%) for discriminating diabetes vs non-diabetes, ≥ 44 mmol/mol (6.2%) and ≥39 mmol/mol (5.7%) for discriminating diabetes vs prediabetes (excluding normoglycaemia), ≥39 mmol/mol (5.7%) and ≥37 mmol/mol (5.5%) for discriminating dysglycaemia vs normoglycaemia, and ≥39 mmol/mol (5.7%) and ≥37 mmol/mol (5.5%) for discriminating prediabetes vs normoglycaemia (excluding diabetes), in black and white people, respectively.Conclusions Consistently higher optimal HbA 1c thresholds in black people than in white people suggest a need to individualize HbA 1c relative to glucose levels if HbA 1c is used to diagnose diabetes and prediabetes.

Learning about diabetes through epidemiology

“…In the cross‐sectional US National Health and Nutrition Examination Survey (NHANES) 2005–2014, Ford et al . compared the use of HbA 1c to define diabetes, with the fasting and 2‐h plasma glucose criteria as the gold standard . This yielded different ‘optimal’ HbA 1c thresholds for defining diabetes in the two ethnic groups studied: 42 mmol/mol (6.0%) for people of African ancestry and 39 mmol/mol (5.7%) for people of white European ancestry.…”

Cardiometabolic risk factors and cardiovascular disease predictions in older African and European Americans

“…This was different from another study which found that AA had higher blood pressure than EA ( Lee-Frye and Shah, 2022 ) but participants were younger in that study. Although AA had higher HbA1c and a trend toward higher TG values, the findings of few CMO risk factors that differed from EA was surprising and may have been partially the results AA having higher HDLs ( Ford et al, 2019 ).…”

Systematic review and meta‐analysis of patient race/ethnicity, socioeconomics, and quality for adult type 2 diabetes

“…Relative to whites, black and Hispanic patients had lower performance in intermediate outcomes but higher performance in many process measures. Recent studies suggest some of the differences between race/ethnic groups in intermediate outcomes may be attributable to biologic differences such as higher risk of hypertension among black patients 41 . Performance across both intermediate outcomes and process measures tended to rise with education although meta‐analyses found only two of the eight measures were statistically significant.…”