Recommended Methods for Glucose Testing in Diabetic Patients
The most effective approach to glucose testing in diabetic patients includes self-monitoring of blood glucose (BGM) for day-to-day management combined with regular HbA1c testing every 3 months to assess long-term glycemic control. 1
Primary Testing Methods
Blood Glucose Monitoring (BGM)
- Sample collection: Venous plasma is recommended for diagnosis, while capillary blood (fingerstick) is appropriate for routine monitoring 1
- Testing frequency:
HbA1c Testing
- Frequency: Every 3 months for patients not meeting glycemic targets or with therapy changes; twice yearly for patients with stable glycemic control 1
- Target values:
- General target: <7% for most adults
- Stricter target (6.5% or <7%): For younger patients with short duration of diabetes and no significant cardiovascular disease
- Less strict target (up to 8%): For older adults (≥65 years), history of severe hypoglycemia, or limited life expectancy 2
Specific Testing Technologies
Laboratory Testing
- Enzymatic methods: Hexokinase or glucose oxidase methods are most common (used in >99% of laboratories) 1
- Sample collection tubes: Citrate-containing tubes (citric acid, sodium citrate, EDTA) are recommended to prevent glycolysis and ensure accurate results 1
- Performance standards: Laboratory methods should aim for imprecision ≤2.2% CV with 0% bias to minimize misclassification of patients 1
Home Glucose Meters
- Accuracy standards: FDA requires 95% of readings to be within 15% of actual blood glucose values 2
- Reporting: Meters should report glucose concentrations in plasma equivalent values 1
- Quality control: Regular evaluation of monitoring technique and use of calibration/control solutions are essential 1
- Important note: Portable glucose meters should NOT be used for diagnosing diabetes 1, 2
Continuous Glucose Monitoring (CGM)
- Benefits: Provides trend data and patterns to detect hypoglycemia and hyperglycemia 2
- Options: Include Abbott FreeStyle Libre, Dexcom G6, and Medtronic systems 2
- Advantages: Newer factory-calibrated CGMs eliminate need for fingerstick calibration and have minimal lag time (4-12 minutes) between blood and interstitial glucose 1
- Special populations: May be particularly valuable for patients with advanced chronic kidney disease who have higher risk for severe hypoglycemia 1
Clinical Considerations
Postprandial Testing
- Postprandial monitoring is recommended for individuals with preprandial values within target but HbA1c values above target 2
- Postprandial and extended postprandial glucose may be better predictors of glycemic control than fasting glucose in type 2 diabetes 3
Special Situations
- Hospital settings: Professional-use meters with higher accuracy standards should be used in hospitals and acute care facilities 1
- Newborns: Only meters specifically intended for use in newborns should be used due to hematocrit considerations 1
- Advanced kidney disease: Patients with advanced CKD have higher risk for severe hypoglycemia and may benefit from CGM technology 1
Common Pitfalls to Avoid
- Using counterfeit test strips, which can lead to inaccurate results 2
- Not using results to guide therapy adjustments 2
- Failing to consider factors affecting accuracy (oxygen levels, medications, environmental factors) 2
- Using portable meters for diagnosis rather than monitoring 1, 2
- Not accounting for the difference between whole blood and plasma glucose values (plasma values are approximately 11% higher) 1
By implementing these recommended glucose testing methods and understanding their appropriate applications, healthcare providers can optimize the monitoring and management of diabetic patients, ultimately improving morbidity, mortality, and quality of life outcomes.