HbA1c Versus HbA1c-Hemoglobin Ratio to Predict Mortality in Patients With T2D, CKD

Chronic kidney disease (CKD) is common among patients who have type 2 diabetes (T2D). Both the American Diabetes Association and Kidney Disease: Improving Global Outcomes recommend regular evaluation of glycated hemoglobin A1c (HbA1c) to assess long-term glycemic control. However, an ideal HbA1c level for patients with both CKD and T2D has not been determined. The association of HbA1c with mortality also remains unclear.

A study conducted by Seng-Wei Ooi and others attempted to evaluate the association between mean HbA1c, visit-to-visit HbA1c, and HbA1c-hemoglobin (HH) ratio with all-cause mortality and cardiovascular mortality among T2D patients with CKD. Results appeared in BMC Nephrology.

The researchers identified 16,868 T2D patients with stage 3 or higher CKD from outpatient visits to Far Eastern Memorial Hospital in Taiwan between 2003 and 2018. They established all-cause mortality and cardiovascular mortality by linking to Taiwan’s National Death Registry. Most (55.45%) subjects were middle-aged (50-69 years); mean age was 63.61 ± 11.84 years. The population was split almost equally between male and female. Mean HbA1c of most (58.90%) subjects was around 6.00% to 7.90%, 44.96% were prescribed insulin, and 68.85% had stage 3a CKD. In addition, 58.54% had anemia and 29.36% had low mean albumin levels (<3.5 g/dL).

The research team estimated mortality rates using the Poisson distribution, and they conducted Cox proportional hazards regressions to determine relative risks of mortality corresponding to the mean HbA1c, average real variability (ARV) of HbA1c, and HH ratio. During a mean follow-up period of 8 years, 6857 (40.65%) patients experienced all-cause mortality, while 1357 (8.04%) experienced cardiovascular mortality.

HbA1c-ARV proved better than mean HbA1c or HH ratio at predicting mortality. Compared with patients with a mean HbA1c of 7.0% to 7.9%, a mean HbA1c <7.0% was consistently associated with the highest risk of all-cause mortality, but not cardiovascular mortality, after adjusting for confounders. Meanwhile, patients with HbA1c-ARV in the second to fourth quartiles and HH ratios in the higher quartiles demonstrated an increased risk of all-cause mortality and cardiovascular mortality versus those in the first quartiles.

The study’s limitations include a lack of data on body mass index and smoking, which may affect survival; differing clinical conditions during hemoglobin blood draws, which may confound results; and the single-center design, which limits generalizability.

“Our study found that in T2D patients with CKD, lower mean HbA1c (<7%) was associated with all-cause but not cardiovascular mortality,” the authors concluded. “HbA1c-ARV could more effectively predict both all-cause and cardiovascular mortality compared [with] HH ratio. In daily clinical practice, we should implement integrated and multifaceted diabetes care to optimize glucose control and minimize glycemic variability in T2D patients with CKD.”

Source: BMC Nephrology