Mean blood glucose-independent HbA1c racial disparity and iron status in youth with Type 1 DM

Determination of Glucose-Independent Racial Disparity in HbA1c for Youth With Type 1 Diabetes in the Era of Continuous Glucose Monitoring

BACKGROUND

The magnitude and importance of higher HbA1c levels not due to mean blood glucose (MBG) in non-Hispanic black (B) versus non-Hispanic white (W) individuals is controversial. We sought to clarify the relationship of HbA1c with glucose data from continuous glucose monitoring (CGM) in a young biracial population.

METHODS

Glycemic data of 33 B and 85 W, healthy youth with type 1 diabetes (age 14.7 ± 4.8 years, M/F = 51/67, duration of diabetes 5.4 ± 4.7 years) from a factory-calibrated CGM was compared with HbA1c. Hemoglobin glycation index (HGI) = assayed HbA1c - glucose management index (GMI).

RESULTS

B patients had higher unadjusted levels of HbA1c, MBG, MBGSD, GMI, and HGI than W patients. Percent glucose time in range (TIR) and percent sensor use (PSU) were lower for B patients. Average HbA1c in B patients 8.3% was higher than 7.7% for W (P < .0001) after statistical adjustment for MBG, age, gender, insulin delivery method, and accounting for a race by PSU interaction effect. Higher HbA1c persisted in B patients when TIR was substituted for MBG. Predicted MBG was higher in B patients at any level of PSU. The 95th percentile for HGI was 0.47 in W patients, and 52% of B patients had HGI ≥ 0.5. Time below range was similar for both.

CONCLUSIONS

Young B patients have clinically relevant higher average HbA1c at any given level of MBG or TIR than W patients, which may pose an additional risk for diabetes complications development. HGI ≥ 0.5 may be an easy way to identify high-risk patients.

Can HbA1c Alone Be Safely Used to Guide Insulin Therapy in African Youth with Type 1 Diabetes?

Introduction

The relationship of HbA1c versus the mean blood glucose (MBG) is an important guide for diabetes management but may differ between ethnic groups. In Africa, the patient's glucose information is limited or unavailable and the management is largely guided by HbA1c. We sought to determine if the reference data derived from the non-African populations led to an appropriate estimation of MBG from HbA1c for the East African patients.

Methods

We examined the relationship of HbA1c versus MBG obtained by the continuous glucose monitoring in a group of East African youth having type 1 diabetes in Kenya and Uganda (n = 54) compared with the data obtained from A1c-derived average glucose (ADAG) and glucose management indicator (GMI) studies. A self-identified White (European heritage) population of youth (n = 89) with type 1 diabetes, 3-18 years old, living in New Orleans, LA, USA metropolitan area (NOLA), was studied using CGM as an additional reference.

Results

The regression equation for the African cohort was MBG (mg/dL) = 32.0 + 16.73 × HbA1c (%), r = 0.55, p < 0.0001. In general, the use of the non-African references considerably overestimated MBG from HbA1c for the East African population. For example, an HbA1c = 9% (74.9 mmol/mol) corresponded to an MBG = 183 mg/dL (10.1 mmol/L) in the East African group, but 212 mg/dL (11.7 mmol/L) using ADAG, 237 mg/dL (13.1 mmol/L) using GMI and 249 mg/dL (13.8 mmol/L) using NOLA reference. The reported occurrence of serious hypoglycemia among the African patients in the year prior to the study was 21%. A reference table of HbA1c versus MBG from the East African patients was generated.

Conclusions

The use of non-African-derived reference data to estimate MBG from HbA1c generally led to the overestimation of MBG in the East African patients. This may put the East African and other African patients at higher risk for hypoglycemia when the management is primarily based on achieving target HbA1c in the absence of the corresponding glucose data.

Glucose-independent racial disparity in HbA1c is evident at onset of type 1 diabetes

OBJECTIVE

Higher levels of HbA1c, independent of blood glucose levels, have been described in Blacks compared to Whites patients with established diabetes. The goal of this study was to determine if glucose-independent racial disparity in HbA1C is evident at diabetes onset.

RESEARCH DESIGN AND METHODS

We conducted a retrospective single-center chart review of 189 youth with new onset Type 1 diabetes (T1D) 60 % Whites and 40 % Blacks. HbA1c, glucose and other biochemistry measures were obtained at presentation in the Emergency Department before initiation of any therapy. HbA1c levels were adjusted for presenting glucose, self-identified race, age, gender, hematocrit, and RDW-CV.

RESULTS

Blacks with T1D had statistically significant higher unadjusted HbA1c (11.9 ± 1.9 vs 11.04 ± 2.0 %, p = 0.004), initial glucose (530.6 ± 230.4 vs 442 ± 211.3 mg/dL, p = 0.0075) and lower pHs (7.28 ± 0.15 vs 7.33 ± 0.12, p = 0.02) compared to white patients. Least squares means of HbA1c remained higher in Black patients even after statistical adjustment for presenting glucose, age, gender, RDW-CV, and pH. In a multiple variable model (R² = 0.38, p < 0.0001) c-peptide was influenced by HCO₃ (p = 0.0035), gender (p = 0.0092), BMI (p < 0.0001), but not race or glucose.

CONCLUSIONS

HbA1c at initial presentation of T1D is higher in young Black patients compared to Whites even after adjustment for glucose, age, gender, and RDW-CV. This racial disparity is consistent with other studies in individuals without diabetes and patients with long-standing diabetes under treatment.

Can Innovative Technologies Overcome HbA1c Disparity for African-American Youth with Type 1 Diabetes?

Achieving normal or near-normal glycemic control as reflected by HbA1c levels in patients with type 1 diabetes (T1D) is important for preventing the development and progression of chronic complications. Despite delineation and dissemination of HbA1c management targets and advances in insulin pharmacology, insulin delivery systems, and glucose monitoring, the majority of children with T1D do not achieve HbA1c goals. In particular, African Americans are more likely not to reach HbA1c goals and have persistently higher HbA1c than Non-Hispanic Whites. Availability of pumps and other technology has not eliminated the disparity in HbA1c. Multiple factors play a role in the persisting racial disparity in HbA1c outcome. The carefully designed application and deployment of new technology to help the patient/family and facilitate the supportive role of the diabetes management team may be able to overcome racial disparity in glycemic outcome and improve patient quality of life.