The principle of the dry-hematology system.  As the blood sample is clotted, particle movement is decreased.  Clotting time is measured in seconds and correlated to fibrinogen concentrations.  (Image source: Anesthesia & Analgesia)

The principle of the dry-hematology system. As the blood sample is clotted, particle movement is decreased. Clotting time is measured in seconds and correlated to fibrinogen concentrations. (Image source: Anesthesia & Analgesia)

For patients undergoing cardiopulmonary bypass, measures of fibrinogen can guide hemostasis therapy. Typically, fibrinogen assays take 30-60 minutes, during which therapy may be delayed. Dr. Satoru Ogawa, Department of Anesthesiology, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, Japan, and colleagues from the Department of Anesthesiology, University of Pittsburgh, Pittsburgh, Pennsylvania, and the Research Institute, A&T Corporation, Kanagawa, Japan, tested the performance of a new laboratory system, the dry-hematology system (DRIHEMATO®), for measuring fibrinogen levels in whole blood or plasma. The results of their study are published in this month’s issue of Anesthesia & Analgesia in the article titled “Fibrinogen Measurements in Plasma and Whole Blood: A Performance Evaluation Study of the Dry-Hematology System.”

The dry-hematology system is similar to existing viscoelastic systems: it assesses fibrinogen levels by measuring the rate of thrombin-induced clot formation in a blood sample mingled with paramagnetic iron oxide particles. The sample is placed in an oscillating magnetic field and the motion of the particles is measured. As a clot forms, particle motion is restricted. The resulting derived values and graphics are superficially similar to the output of a thromboelastograph. The authors evaluated this system in whole blood and plasma drawn from healthy volunteers, and in samples from cardiac surgery patients. Samples were divided into aliquots with various degrees of dilution and tested with and without the presence of heparin in the sample.

The system generally performed well. Fibrinogen levels in plasma were consistent with those derived from existing standard of care devices and were not affected by the presence of heparin or colloids in the sample. Fibrinogen levels varied considerably in whole blood samples, but a simple adjustment for hematocrit corrected this issue. The clinical relevance of the dry-hematology system has yet to be established, and it is uncertain if this technology will gain market share relative to thromboelastography or thromboelastometry.

Based on the need for sample dilution and machine calibration, this new dry hematology assay will not be a bedside test. Nonetheless, development of the dry-hematology method indicates rising recognition that fibrinogen level is critical in assessing coagulation. More options for accurately tracking fibrinogen will improve the precision of hemostasis management.