Properties of Optical Data from Activated Partial Thromboplastin Time and Prothrombin Time Assays

Abstract

SummaryChanges in characteristics of optical transmittance data from coagulation assays were examined as a function of concentration of coagulation proteins or anticoagulants. Transmittance data were collected for activated partial thromboplastin time (APTT) and prothrombin time (PT) assays from: 1) plasmas prepared by mixing normal plasmas with deficient plasmas to give varying levels of coagulation proteins; 2) plasmas containing added heparin; and 3) 200 specimen plasmas that were also assayed for fibrinogen, coagulation factors, and other components. Optical profiles were characterized using a set of parameters describing onset and completion of coagulation, magnitude of signal change, rate of coagulation and other properties. Results indicated that parameters other than those typically reported for APTT and PT are associated with individual deficiencies, but that diagnosis of specimen status on the basis of optical data is complex. These results suggest possibilities for expanded interpretation of PT/APTT optical data for clinical or research applications.

Reflectance Changes in Clotting Native Blood: Evidence of a Red Cell Process

“…Blombäck and Okada [7] attribute the phenomenon to the presence of factor XIII, even in trace amounts, because factor XIIIa requires Ca 2+ and catalyses fibrin cross-linking. Consistent with this explanation, optical systems designed to study recalcified plasma report little deflection until after the clot point [8] . Clotting blood, which contains both Ca 2+ and factor XIII, also fits this pattern [1] .…”

Biphasic transmittance waveform in the APTT coagulation assay is due to the formation of a Ca++-dependent complex of C-reactive protein with very-low–density lipoprotein and is a novel marker of impending disseminated intravascular coagulation

“…The methodology has been described in detail elsewhere. [1][2][3][4] In brief, the MDA 180 uses a variable wavelength photo-optical detection system and can chart and quantify changes in light transmission when the plasma clots after activation and recalcification. Normal and biphasic waveforms at 580 nm are illustrated in Figure 1.…”

“…1,2 The biphasic waveform (BPW) was initially described when a decrease in plasma light transmittance before clot formation on the MDA 180 automated coagulation analyzer was shown to correlate with disseminated intravascular coagulation (DIC) in critically ill patients. [3][4][5] In contrast to the normal sigmoidal waveform pattern that is characterized by an initial 100% light transmittance phase before clot formation, patients with a biphasic pattern had an immediate, progressive decrease in light transmittance that occurred even in the preclotting phase.…”

“…with BPW of varying severity and DIC arising from sepsis (7), pancreatitis (2), respiratory distress syndrome (2), ruptured abdominal aortic aneurysm (1), and trauma. At the time of sampling, 7 patients required assisted ventilation, 3 required enteral feeding, and 2 required total parenteral nutrition.…”

Tests of global haemostasis and their applications in bleeding disorders

“…The process of thrombin generation and fibrin clot formation can be captured with greater sensitivity and completeness by tests that measure global haemostasis. These include the thrombin generation tests/assay (TGT/ TGA) [5,7], thromboelastography(TEG) [8] and the activated partial thromboplastin time (APTT) waveform analysis (WA) [9] using different instrument systems. These tests have not only helped in more complete assessment of the process of normal haemostasis but have also provided newer insights into the evaluation of disorders of haemostasis.…”