What is the likelihood of diabetes with a plasma glucose of 6.2 mmol/L and HbA1c of 4.9%?

Assessment of Diabetes Risk with Plasma Glucose 6.2 mmol/L and HbA1c 4.9%

Based on the current diagnostic criteria, a plasma glucose of 6.2 mmol/L and HbA1c of 4.9% do not indicate diabetes, but the plasma glucose value falls within the impaired fasting glucose (IFG) range, suggesting prediabetes.

Diagnostic Interpretation

Analysis of Values

• Plasma glucose of 6.2 mmol/L (112 mg/dL):

  • This value falls within the range of impaired fasting glucose (IFG) according to both WHO and ADA criteria
  • WHO defines IFG as 6.1-6.9 mmol/L (110-125 mg/dL) 1
  • ADA defines IFG as 5.6-6.9 mmol/L (100-125 mg/dL) 1

• HbA1c of 4.9%:

  • This is below the prediabetes threshold of 5.7-6.4% 1
  • Well below the diabetes diagnostic threshold of ≥6.5% 1

Diagnostic Classification

1. Not diabetes: Both values are below diabetes thresholds

   • Diabetes diagnosis requires:
     • HbA1c ≥6.5% OR
     • Fasting plasma glucose ≥7.0 mmol/L (126 mg/dL) OR
     • 2-hour plasma glucose ≥11.1 mmol/L (200 mg/dL) during OGTT 1

2. Possible prediabetes: The plasma glucose of 6.2 mmol/L meets criteria for IFG, but the HbA1c does not meet prediabetes criteria

Clinical Implications

Discordance Between Glucose and HbA1c

The discordance between the elevated plasma glucose and normal HbA1c is notable:

• This pattern suggests:

  • Possible isolated postprandial hyperglycemia
  • Recent onset of glycemic abnormalities not yet reflected in HbA1c
  • Possible measurement during stress/illness (transient hyperglycemia)

• Research shows that when using both FPG and HbA1c for diagnosis, the prevalence of prediabetes increases significantly compared to using FPG alone 2

Risk Assessment

• The plasma glucose of 6.2 mmol/L indicates impaired fasting glucose, which carries:

  • Increased risk for progression to diabetes
  • Modestly increased cardiovascular risk 1

• However, the normal HbA1c suggests that chronic hyperglycemia is not present

Recommended Follow-up

1. Confirm fasting status:

   • Verify if the plasma glucose measurement was truly fasting (≥8 hours)
   • If not fasting, interpret with caution as random glucose values have different diagnostic thresholds

2. Consider repeat testing:

   • Repeat fasting plasma glucose to confirm IFG
   • Consider OGTT to assess postprandial glucose metabolism, especially if clinical suspicion for glucose intolerance exists 1

3. Risk factor assessment:

   • Evaluate for other diabetes risk factors (obesity, family history, hypertension, dyslipidemia) 1

Important Caveats

• Single measurements are insufficient: Diagnosis should not be based on a single abnormal value unless symptoms of hyperglycemia are present 1

• HbA1c limitations: HbA1c may be affected by:

  • Hemoglobinopathies
  • Conditions affecting red cell turnover
  • Ethnicity 1

• Plasma glucose variability: Day-to-day variability in glucose levels can affect interpretation of a single measurement 3

In conclusion, while the patient does not meet criteria for diabetes, the elevated fasting plasma glucose suggests prediabetes (IFG). Further testing and risk factor assessment are warranted to determine appropriate monitoring and preventive interventions.