History of the preanalytical phase: a personal view

In the 70ies of the last century, ther term “preanalytical phase” was introduced in the literature. This term describes all actions and aspects of the “brain to brain circle” of the medical laboratory diagnostic procedure happening before the analytical phase. The author describes his personal experiences in the early seventies and the following history of increasing awareness of this phase as the main cause of “laboratory errors”. This includes the definitions of influence and interference factors as well as the first publications in book, internet, CD-Rom and recent App form over the past 40 years. In addition, a short summary of previous developments as prerequesits of laboratory diagnostic actions is described from the middle age matula for urine collection to the blood collection tubes, anticoagulants and centrifuges. The short review gives a personal view on the possible causes of missing awareness of preanalytical causes of error and future aspects of new techniques in regulation of requests to introduction of quality assurance programs for preanalytical factors.     

Pharmacogenetic Aspects of Coumarinic Oral Anticoagulant Therapies

Coumarinic oral-anticoagulants (COAs) are commonly used for treatment of thromboembolic events. However, these medications have a narrow therapeutic range and there are large inter-individual variations in drug response. This is especially important in the initial phases of oral-anticoagulant therapy. Recent advancements in pharmacogenetics have established that clinical outcomes in oral-anticoagulant therapy are affected by genetic factors. The allelic variants of genes like cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex subunit 1 (VKORC1) are closely associated with maintenance dose of oral anti-coagulants. In addition, GGCX (Gamma-glutamyl carboxylase) polymorphism at position 12970 (rs11676382), CYP4F2 (rs2108622; V433M; 1347 C > T) and Apolipoprotein E (APOE) variants have been shown to explain a small but significant influence on dose requirements. There are large differences in the frequencies of these polymorphisms between different world populations which are also related to the requirements of oral anticoagulants. However, the final drug dosage in an individual is determined by complex sets of genetic and environmental factors and several dosing algorithms which combine clinical and genetic parameters to predict therapeutic COA doses have also been developed. The algorithm based dose prediction shows the importance of pharmacogenetic testing in patients undergoing oral anticoagulant therapies.     

The new oral anticoagulants and the future of haemostasis laboratory testing

The tests currently employed within most haemostasis laboratories to monitor anticoagulant therapy largely comprise the prothrombin time (PT)/ International Normalised Ratio (INR) and the activated partial thromboplastin time (APTT). These are respectively used to monitor Vitamin K antagonists (VKAs) such as warfarin, and unfractionated heparin. Additional tests that laboratories may also employ for assessing or monitoring unfractionated heparin include thrombin time (TT) and the anti-Xa assay, which can also be used to monitor low molecular weight heparin. Several new anti-thrombotic agents have recently emerged, or are in the final process of clinical evaluation. These novel drugs that include Dabigatran etexilate and Rivaroxaban would not theoretically require monitoring; however, testing is useful in specific situations. The tests currently used to monitor VKAs and heparin are typically either too sensitive or too insensitive to the new drugs to be used as ‘typically performed in laboratories’, and may thus require some methodological adjustments to increase or decrease their sensitivity. Alternately, different tests may be better employed in these assessments. Whatever the case, laboratories may soon be performing a reduced or possibly increased number of tests, the same kind of tests but perhaps differently, or conceivably different assay panels. Specific laboratory guidance on the choice of the appropriate test to be ordered according to the drug being administered, as well as on appropriate interpretation of test results, will also be necessary. The current report reviews the current state of play and provides a glimpse to the possible future of the coagulation laboratory.