Coagulation assays–An overview
Coagulation analyzers have come a long way from measuring the optical density of a clot in a cuvette to a combination of clotting, chromogenic & immunological assays for screening of normal hemostatic system. Abnormalities of the hemostatic system may be the result of anticoagulant therapy, underlying genetic mutations, or acquired pathologies. The prothrombin time (PT) testing usually accounts for the largest share of the coagulation analyzers market, followed by activated partial thromboplastin time. Specific coagulation factor levels and activities are also measured at specialty laboratories to test patients at risk of hypercoagulability. Laboratory tests of platelet function, like bleeding time, light transmission platelet aggregation, lumiaggregometry, impedance aggregometry on whole blood, and platelet activation, investigated by flow cytometry, are utilized for diagnosing platelet and hemostatic defects, but their use is still limited to specialized laboratories. Coagulation also initiates fibrinolysis, the products of which arereleased into circulation and can be measured as fibrinogen degradation products or D-dimers. D-dimers are more specific for identification of clot formation and breakdown and measured using immunoturbidity or ELISA.
In the recent past, the numbers of coagulation screening tests ordered have increased tremendously. This, in turn, has improved the efficiency of automated coagulation testing, enabling the generation of high-throughput, accurate, and precise analyzers with minimal human error in measurement. Nevertheless, incorrect or inappropriate test results are still reported, primarily due to pre-analytical events associated with sample collection and processing.These issues present a difficult scenario for laboratories as they are often outside the control of the laboratory performing the tests. For this reason, guidelines for specimen collection and handling must be strictly followed and deviations avoided.
Although laboratory determination of PT/INR from blood obtained by venipuncture remains the gold standard for monitoring INR, point-of-care (PoC) PT/INR measurement offers significant advantages as a decision and management tool, both in and out of the hospital. The need for PoC coagulation technologies becomes necessary as centralized laboratories are often unable to provide results in the time frames, which would allow timely intervention of anticoagulant therapy. In this regard, advanced technologies, such as microfluidics, fluorescent microscopy, electrochemical sensing, photoacoustic detection, and micro/nano electromechanical systems (MEMS/NEMS) have been employed to develop highly accurate, robust, and cost-effective PoC devices. These devices measure electrochemical, optical, and parameters of clotting blood, which can be correlated to light transmission/scattering, electrical impedance, and viscoelastic properties. However, it is important to ensure that PoC testing done by patients, receiving anticoagulants, or technologists provide results which are comparable with those of the central coagulation laboratory.
Automated technologies have revolutionized the monitoring of coagulation disorders in the central hospital laboratory setting, allowing for high-throughput testing, improved accuracy and precision, accompanied by a marked reduction in human error. T2 magnetic resonance, use of acoustic waves, andinfrared techniques are some new and emerging technologies that are able to detect clot formation. In development stages, the platelet contraction cytometer is a small device that can assess platelet contractile forces, and preliminary studies suggest that it may identify some patients with a bleeding tendency that cannot otherwise be identified by existing laboratory tests.
The coagulation analyzers in the Asian market are expected to grow owing to rising incidence of blood-related disorders, such as thalassemia, sickle-cell anemia, leukemia, rising number of general surgeries, and owing to rapidly growing geriatric population. Moreover, the increasing awareness about these conditions is anticipated to improve the preventive care management and diagnostic rate, which is expected to substantially drive the global special coagulation test market.
