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Standardization of low molecular weight heparins: a collaborative study.
Thrombosis and Haemostasis
|October 30, 1985
Summary
Low molecular weight heparins (LMWH) cannot be reliably measured against the International Standard using current assays. A single LMWH standard and assay method are needed for accurate and consistent heparin potency determination.
Area of Science:
- Pharmacology
- Biochemistry
- Analytical Chemistry
Background:
- Low molecular weight heparins (LMWH) are widely used anticoagulants derived from unfractionated heparin.
- Accurate potency determination of LMWH is crucial for effective therapeutic use and patient safety.
- Existing international standards and assay methods may not adequately reflect the specific properties of LMWH.
Purpose of the Study:
- To evaluate the suitability of current assay methods and the International Standard (IS) for quantifying low molecular weight heparins (LMWH).
- To assess inter-laboratory and inter-assay variability in LMWH potency determination.
- To propose improvements for accurate and reliable LMWH standardization.
Main Methods:
- A collaborative study involving eight laboratories.
- Assay of eight different LMW heparins against the heparin International Standard (IS).
- Utilized activated partial thromboplastin time (APTT) assays and three distinct anti-factor Xa (anti-Xa) methods.
Main Results:
- LMW heparins cannot be validly assayed against the IS using either APTT or anti-Xa methods.
- Significant differences in LMWH potencies were observed between assay methods and laboratories.
- Potency results varied considerably when LMW heparins were assayed against the IS.
Conclusions:
- Current methods and the IS are inadequate for the reliable assay of LMWH.
- Adopting a single, specific LMWH standard is essential to improve assay validity and reduce inter-laboratory variation.
- A single, standardized assay method, such as plasma anti-Xa amidolytic assay, should be selected for calibrating the LMWH standard.