The myths behind DOAC measurement: Analyses of prescribing information from different regulatory bodies and a call for harmonization

For more than a decade, US laboratories have failed to implement solutions to help their clinicians in managing complex situations or patients on direct oral anticoagulants (DOACs). The problem may find different origins, among which is the position of the Food and Drug Administration, which categorized these drugs as monitoring- and measurement-free, whereas other regulatory bodies like the European Medicines Agency or the Therapeutic Goods Administration in Australia were more conservative on the principle that the absence of proof (of monitoring/measurement benefits) is not proof of an absence (of monitoring/measurement needs). Pivotal clinical studies that led to the approval of DOACs were presented as devoid of such testing, although some companies considered monitoring as a solution to improve their benefit/risk ratio. In this JTH In Clinics issue, we report more than a decade of development that has permitted the activation of smart laboratory solutions to qualify or quantify DOACs and discuss myths and misconceptions around technical and regulatory requirements that support the current reluctance of implementing these technologies in most US laboratories. Use of DOACs is ever expanding, with DOAC prescriptions now exceeding those of other anticoagulants, including vitamin K antagonists, in some geographies. As this use increases, the likely need to measure DOAC exposure will also increase. Measurement of DOACs does not represent any technical difficulty. That these laboratory tests are not available in some locations suggests disparities in patient care, and we suggest it is time to address such inequalities.

Anti-Thrombin, Anti-Adhesive, Anti-Migratory, and Anti-Proliferative Activities of Sulfated Galactans from the Tropical Green Seaweed, Udotea flabellum

In this study, sulfated polysaccharide-rich extracts were isolated from 22 tropical seaweeds (4 red, 11 brown, and 7 green) found in northeastern Brazil, and evaluated for the role of anticoagulant agents. Fifteen of the extracts showed anticoagulant activity, including all the extracts from green seaweeds. Udoteaflabellum (a green seaweed) extract was the most potent, requiring an amount of only 3 µg to double the plasma coagulation time in the activated partial thromboplastin time test. A similar result was obtained with 1 µg of heparin. Two sulfated homogalactans with anticoagulant activity, F-I (130 kDa) and F-II (75 kDa), were isolated from this extract using several bio-guided purification steps. Their anticoagulant activity, as well as properties related to antitumor activity (anti-proliferative, anti-adhesive, and anti-migratory), were accessed. Their anticoagulant activities were close to that of heparin. We found that F-I and F-II (0.5–10 μg/mL) were not able to directly inhibit thrombin. In the presence of anti-thrombin, F-I (0.5 μg/mL) was more effective than heparin (0.5 μg/mL) in inhibiting thrombin, while F-II showed similar effects as heparin. F-I and F-II also inhibited B16-F10 (murine melanoma cells) adhesion, migration, and proliferation on a fibronectin-coated surface, but not on laminin- or collagen I-coated surfaces. Except for the antiproliferative activity, the other effects of F-I and F-II were eliminated upon their desulfation (~50%), indicating that the degree of sulfation is not as important for F-I and F-II anti-proliferative activity as the sulfation position. Taken together, the results provide strong evidence for the potential utility of sulfated galactans from U.flabellum, making these compounds an interesting option for future investigations that aim to design new anticoagulant/antitumor agents.

Disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a reflection of an underlying systemic disorder which affects the coagulation system, simultaneously resulting in pro-coagulant activation, fibrinolytic activation, and consumption coagulopathy and finally may result in organ dysfunction and death. Though septicaemia is the most common cause of DIC, several other conditions can also lead to it. A diagnosis of DIC should be made only in the presence of a causative factor supported by repeated laboratory tests for coagulation profile and clotting factors. An effective scoring system helps to detect an overt DIC and a high score closely correlates with mortality. Treatment of DIC is aimed at combating the underlying disorder followed by supportive management. Low molecular weight heparin is advocated in special situations whereas anti-thrombin III and activated protein C are of doubtful value. Early diagnosis and prompt treatment backed by laboratory support can reduce the morbidity and mortality associated with it. The methodology of search for this review article involved hand search from text books and internet search using Medline (via PubMed) using key words DIC, thrombosis, fibrin degradation products, anti-thrombin and tissue factor for the last 25 years and also recent evidence-based reviews.

The Anopheles gambiae cE5, a tight- and fast-binding thrombin inhibitor with post-transcriptionally regulated salivary-restricted expression

Mosquito saliva carries a large number of factors with anti-hemostatic, anti-inflammatory and immuno-modulatory activities. The cE5 protein was initially identified during an Anopheles gambiae salivary gland transcriptome study and later shown to share sequence similarity with anophelin, a thrombin inhibitor from the saliva of the New World mosquito Anopheles albimanus. The cE5 gene was found to encode different mRNA isoforms coexisting in several tissues of both male and female mosquitoes, a highly unusual profile for a gene potentially encoding an anti-thrombin and involved in blood feeding. Expression of the cE5 protein and assessment of its activity and inhibitory properties showed that it is a highly specific and tight-binding thrombin inhibitor, which differs from the A. albimanus orthologue for the fast-binding kinetics. Despite the widespread occurrence of cE5 transcripts in different mosquito tissues the corresponding protein was only found in female salivary glands, where it undergoes post-translational modification. Therefore, tissue-specific restriction of the A. gambiae cE5 is not achieved by transcriptional control, as common for mosquito salivary genes involved in hematophagy, but by post-trascriptional gene regulatory mechanisms. Our observations provide a paradigm of post-transcriptional regulation as key determinant of tissue specificity for a protein from an important disease vector and point out that transcriptomic data should be interpreted with caution in the absence of concomitant proteomic support.