What are alternative tests to Hemoglobin A1c (HbA1c) for checking glucose levels?

From the Guidelines

Fructosamine or glycated albumin can be used as alternatives to A1C for monitoring glycemic status, especially in individuals with conditions that interfere with A1C interpretation, as recommended by the most recent guidelines 1. When considering alternative tests to hemoglobin A1c for monitoring glucose, it's essential to understand the different options available and their implications for patient care.

• Fructosamine and glycated albumin reflect average glucose levels over a shorter period, typically 2-4 weeks, making them useful for detecting recent changes in glucose control or monitoring patients with conditions that affect red blood cell lifespan, such as hemolytic anemia, recent blood loss, or hemoglobinopathies 1.
• The typical reference range for fructosamine is 200-285 μmol/L, and these assays have been linked to long-term complications in epidemiologic cohort studies, although the evidence base is weaker than that for A1C 1.
• Continuous glucose monitoring (CGM) provides real-time glucose data and metrics like time in range, which can complement or sometimes replace A1c testing, with the glucose management indicator (GMI) calculated from CGM data serving as an estimated A1c equivalent.
• For immediate assessment, point-of-care random glucose testing or laboratory tests like fasting plasma glucose (normal <100 mg/dL) and oral glucose tolerance tests can be used, particularly when A1c results may be unreliable due to conditions affecting red blood cell turnover, pregnancy, or certain genetic variants.
• The most recent guidelines recommend assessing glycemic status by A1C and/or continuous glucose monitoring (CGM) metrics, with fructosamine or CGM as alternatives to A1C when necessary, and suggest assessing glycemic status at least two times a year, or more frequently in certain situations 1.

From the Research

Alternative Markers to Hemoglobin A1c

• Fructosamine and glycated albumin reflect mean blood glucose over a shorter period (three weeks) compared to HbA1c (three months) 2
• 1,5-Anhydroglucitol can measure hyperglycemic excursions in days to weeks, providing a more immediate assessment of glucose control 2
• Continuous glucose monitors offer immediate feedback for timely intervention to reduce glycemic excursions and can assess glycemic variability 2

Comparison of Alternative Markers

• Studies have compared the performance of glycated albumin, fructosamine, and HbA1c in determining glycemic control, with varying results 3, 4, 5, 6
• Fructosamine seems to more accurately reflect glycemic status in patients with type 2 diabetes receiving peritoneal dialysis or hemodialysis 4, 5
• Glycated albumin may provide a better assessment of glycemic control than HbA1c and fructosamine in patients with end-stage kidney disease and burnt-out diabetes 6

Limitations of Alternative Markers

• A lack of standardization for clinically useful cut-offs or guidelines limits the use of alternative markers 2
• Long-term data on the association of alternative markers with complications, particularly in varied patient populations, is lacking 2
• Certain conditions, such as anaemia, can affect the accuracy of alternative markers like fructosamine and HbA1c 3, 4, 5