Can Infection or Illness Affect Fructosamine Values in Pregnant Women with Hyperglycemia?
Yes, infection and illness can significantly affect fructosamine values in pregnant women, making them unreliable markers of glycemic control during acute illness, but the provided evidence does not directly address this specific interaction—therefore, you should rely on plasma glucose measurements and A1C (when standardized) rather than fructosamine for diagnosing and monitoring hyperglycemia in pregnancy.
Why Fructosamine Is Problematic in Pregnancy
Fructosamine has fundamental limitations in pregnancy that are compounded by acute illness:
Physiologic changes in pregnancy already reduce fructosamine levels due to decreased serum albumin concentrations (mean 31.35 ± 3.97 g/L in second trimester versus normal non-pregnant values), making interpretation difficult even in healthy pregnant women 1
Fructosamine shows poor diagnostic performance for gestational diabetes, with sensitivity of only 54.8% and specificity of 48.6% at the median threshold of ≥222 µmol/L, yielding an area under the ROC curve of just 0.52 2
The correlation between fructosamine and actual glycemic control is weak to moderate at best in pregnant women with diabetes, with a determination coefficient of only R² = 0.265 for predicting hyperglycemia 3
How Infection/Illness Would Further Compromise Fructosamine
While the provided evidence doesn't explicitly address infection effects on fructosamine in pregnancy, acute illness would be expected to:
- Alter protein metabolism and turnover, affecting the glycation of serum proteins that fructosamine measures
- Change albumin levels through inflammatory responses, capillary leak, or altered hepatic synthesis
- Cause acute hyperglycemia from stress hormones and insulin resistance, which fructosamine (reflecting 1-3 week average) would not capture acutely 1
What You Should Use Instead
For diagnosis of hyperglycemia in pregnancy:
Measure fasting plasma glucose using venous plasma or serum glucose with an enzymatic method with high accuracy and precision, including proper sample collection to minimize pre-analytic glycolysis 4
Diagnostic thresholds are: FPG ≥5.1 mmol/L (92 mg/dL) for GDM, or FPG ≥7.0 mmol/L (126 mg/dL) for overt diabetes 4
A1C ≥6.5% (using DCCT/UKPDS standardized method) confirms overt diabetes, though hemoglobin variants are prevalent in some populations and must be considered 4
For GDM screening at 24-28 weeks: perform a 75-g OGTT after overnight fast, with diagnostic thresholds of FPG ≥5.1 mmol/L (92 mg/dL), 1-hour ≥10.0 mmol/L (180 mg/dL), or 2-hour ≥8.5 mmol/L (153 mg/dL)—only one abnormal value needed 4
For monitoring glycemic control during pregnancy:
Self-monitoring of blood glucose (fasting and postprandial) is the primary method, with targets of fasting 70-95 mg/dL, 1-hour postprandial 110-140 mg/dL, or 2-hour postprandial 100-120 mg/dL 5, 6
A1C should be monitored monthly with target <6% if achievable without significant hypoglycemia, but it serves as a secondary measure, not the primary metric 5, 6
Critical Pitfalls to Avoid
Do not use fructosamine for screening or diagnosis of gestational diabetes—it cannot replace OGTT and has limited value particularly for mild glucose intolerance 7, 1
Do not rely on fructosamine during acute illness when you need accurate assessment of current glycemic status
Capillary and venous plasma glucose concentrations are not interchangeable, and conversion factors do not accurately estimate equivalent values 4
Ensure proper laboratory technique as small changes in glucose concentration substantially affect diagnostic classification and outcome risks 4