Coagulation Reference Laboratory (CRL)
Services offered
We perform ISI calibration by Manual Tilt tube technique (MTT) (Click here) by using Standards for Tromboplastin according to WHO guidelines
- International standard for recombinant human thromboplastin
- International standard for rabbit brain thromboplastin
Establishment of a Reference Measurement System
…Services offered
We perform ISI calibration by Manual Tilt tube technique (MTT) (Click here) by using Standards for Tromboplastin according to WHO guidelines
- International standard for recombinant human thromboplastin
- International standard for rabbit brain thromboplastin
Establishment of a Reference Measurement System
Oral anticoagulant therapy with vitamin K antagonists (VKA) must be monitored in each patient with a laboratory test of the coagulant activity of the patient’s blood. Among all tests, the prothrombin time (PT), i.e. the tissue factor-induced coagulation time is the most used. However, many different reagents and techniques are applied for this test causing that the PT is expressed in many different ways. This led to serious misconceptions with respect to the optimal therapeutic range for VKA treatment.
Intoducion of the Calibration model and Point-of-care testing (POCT)
Introduction Calibration model
Thromboplastins vary in their sensitivity (i.e. respons) to the coagulation defect by VKA.
To provide means of standardizing PT testst, the World Health Organization adopted e revised model for calibrating thromboplastins in term of an International Reference Preparation (IRP). In this model thromboplastin’s calibration line slope was defined as the International Sensivity Index (ISI). A patient’s INR could be calculated with the equation: INR=(PT/MNTP)ISI in which MNPT is denote the Mean Normal PT.
Introduction Point-of-care INR testing
Point-of-care (POC) procedures have been developed for INR testing that need less technical expertise because they use unmeasured whole blood samples and may be used by patients for self-testing. Accuracy, precision and stability of POC systems for INR testing have been assessed in a series of studies.
Today many patients treated with VKA use POC systems for self-testing and self-management.
Uncertainty of the INR
The use of the INR enables comparisons to be made between results obtained with different thromboplastins and methods. It is a misconception that for an individual patient’s plasma the INR will always be identical with different thromboplastins and methods.
Different thromboplastins vary greatly in their responsiveness to individual vitamin K dependent clotting factors, as well as to some non-vitamin K dependent factors. Discrepancies between INRs determined with different thromboplastins arising from these biological variations and from additional technical errors are therefore not unexpected. Studies in individual patients who were monitored with two different PT reagents for several months, showed that there could be consistent INR differences between the reagents amounting to approximately 0.5 INR
Key publications
Our team members
- Dhr. Dr. A.M.T.H. (Ton) van den Besselaar; Consultant CRL
- Supervision of CRL activities by prof. dr. C.M. (Christa) Cobbaert; Head of Department of Clinical Chemistry and Laboratory Medicine
Contact
Contact
Dhr. Dr. A.M.T.H. (Ton) van den Besselaar (Consultant CRL)
Phone: 071 526 25 16
Supervision of CRL activities by prof. dr. C.M. (Christa) Cobbaert (Head of Department of Clinical Chemistry and Laboratory Medicine)
Adress:
LUMC - Coagulation Reference Laboratory
Department of Clinical Chemistry, location E-2-31
…Contact
Dhr. Dr. A.M.T.H. (Ton) van den Besselaar (Consultant CRL)
Phone: 071 526 25 16
Supervision of CRL activities by prof. dr. C.M. (Christa) Cobbaert (Head of Department of Clinical Chemistry and Laboratory Medicine)
Adress:
LUMC - Coagulation Reference Laboratory
Department of Clinical Chemistry, location E-2-31
Postbus 9600
2300 RC Leiden
The Netherlands