Viral and Rickettsial Hemorrhagic Fevers: Laboratory Investigation of the Hemorrhagic State
James H. S. Gear in CRC Handbook of Viral and Rickettsial Hemorrhagic Fevers, 2019
In interpreting the results of coagulation tests, particular attention should be paid to the relative derangements of PTT and PT. Gross derangements of the PT may indicate significant hepatic pathology, which should be further investigated by liver function tests. Appreciable prolongation of the PTT, on the other hand, with normal or mildly deranged PT, could be consistent with viral hemorrhagic fever. Derangements in either PT or PTT should be followed up by factor assays — in particular, the relative depletions of factor VIII and the “liver” factors should be noted. Depression of antithrombin III levels may be associated with DIC or with liver dysfunction. The thrombin time and fibrinogen determinations are useful markers of qualitative and quantitative fibrinogen status, while fibrin monomers and FDPs could indicate intravascular coagulation and fibrinolytic activity, respectively.
Congenital Platelet Dysfunction and von Willebrand Disease
Harold R. Schumacher, William A. Rock, Sanford A. Stass in Handbook of Hematologic Pathology, 2019
In the screening tests of secondary hemostasis, only the partial thromboplastin time was abnormal. This information is extremely helpful. The observed pattern of results provides no suggestion for a deficiency of coagulation factors participating in the extrinsic pathway or in the common pathway. The normal thrombin time confirms that the patient’s fibrinogen is likely to function normally in coagulation. Certainly the combination of a prolonged bleeding time and a prolonged FIT should immediately raise the question of vWD because, since vWF serves both as a participant with platelets in primary hemostasis and as a carrier for the factor VIII that is critical to secondary hemostasis, a deficiency of vWF would appear capable of explaining all the available findings.
Primary Hyperfibrino(Geno)Lytic Syndromes
Genesio Murano, Rodger L. Bick in Basic Concepts of Hemostasis and Thrombosis, 2019
The usually ordered biochemical survey, electrolytes, and CBC will detect those common acquired disorders often associated with a bleeding tendency, for example: chronic liver disease, chronic renal disease, and instances of hypersplenism or bone marrow failure. Most commonly, a pre-CPB hemostasis screen consists of a prothrombin time, an activated partial thromboplastin time, and a platelet count. While these tests will detect the majority of defects, they provide no information about vascular or platelet function and ignore fibrinolysis. Thus two additional procedures should be performed as part of the routine preoperative screen. A standardized template bleeding time, as described by Mielke and co-workers,66 is performed on all patients. This provides a screen for adequate vascular and platelet function. It should be recalled that this should not be performed until adequate platelet numbers are noted by count or smear evaluation. In addition, a thrombin time is performed. The resultant clot is observed for 5 min after the test is run. A normal thrombin time and the absence of lysis after 5 min assures the absence of significant hypofibrinogenemia, dysfibrinogenemia, fibrinolysis, and/or FDP elevation. The addition of both these tests to the routine presurgical screen adds only minimal cost or laboratory time, while providing additional invaluable information not obtained from a prothrombin time, activated partial thromboplastin time, or platelet count. If hypothermic perfusion is to be performed, cryoglobulins should also be tested for. Table 4 depicts a routine pre-CPB screen and provides references for hemostasis tests.
Perioperative management of anticoagulation
Published in Hospital Practice, 2020
Goutham Talari, Zachary D. Demertzis, Robert D. Summey, Baljinder Gill, Scott Kaatz
Thrombin time can be prolonged when dabigatran levels are below the therapeutic range, but they are always prolonged or out of range when the drug levels are within or above normal range [24,27]. The thrombin time is oversensitive to dabigatran and is prolonged in the presence of the dabigatran. A normal thrombin time excludes the presence of dabigatran, and hence possibly can be used as screening test [27]. Other nonspecific and less sensitive assays like thrombin generation assays, dilute prothrombin time, activated clotting time, prothrombinase induced clotting time, rotational thromboelastometry, endogenous thrombin potential, and thromboelastography are mentioned in the literature but are rarely of practical value at this time, and normal levels do not necessarily exclude important dabigatran levels [24,27].
Rare inherited coagulation disorders in young children in Oman
Published in Pediatric Hematology and Oncology, 2022
Surekha Tony, Roshan Mevada, Abdulhakim Al Rawas, Yasser Wali, Mohamed Elshinawy
Laboratory diagnosis usually starts with the assessment of the coagulation screening tests activated partial thromboplastin time (APTT) and prothrombin (PT). A prolonged APTT with normal PT suggests FXI deficiency after exclusion of FVIII, FIX, and FXII defects. The reverse pattern is usually due to a FVII deficiency, while the prolongation of APTT and PT together suggests the diagnosis of combined FV + FVIII, FX, FV, FII or fibrinogen deficiencies. To evaluate fibrinogen deficiency thrombin time (TT) is also important. When screening coagulation tests are abnormal, mixing analysis (50:50) must be done to exclude the presence of an inhibitor. Therefore, specific factor assays are performed to identify the deficiency. The diagnosis of FXIII defect requires specific tests, because all screening clotting assays are normal. Molecular diagnosis allows to identify the pathogenic mutation in genes that encode corresponding clotting factors.19,20
Characterization of the hemorrhagic syndrome in the New Zealand white rabbit model following total body irradiation
Published in International Journal of Radiation Biology, 2021
Isabel L. Jackson, Ganga Gurung, Emmanuel Ayompe, Elena-Rose Fown, Sarah Triesler, Buddha Mali, Andrea Casildo, Allison Gibbs, Yannick Poirier, Eric P. Cohen, Diana Newman, Zeljko Vujaskovic
Prothrombin time (PT) appeared to be shortened in response to radiation (Figure 4). Shortened activated partial thromboplastin times (aPTT) were observed during the first- to second-week post-exposure, but this did not achieve statistical significance (one-way ANOVA with Tukey’s multiple comparisons test). The shortened prothrombin time was observed at a higher rate among animals in the 7.0 Gy arm (11/19; 57.9%) than the 7.5 Gy arm (n = 9/31; 29%). A shortened thrombin time was observed during the second week post-exposure (e.g. 11−13.8 seconds and 13.4−13.5 seconds, unscheduled vs. scheduled) vs. 14.1−17.8 seconds. However, there was a marked difference in thrombin time between animals euthanized due to study endpoint (scheduled) vs. criteria (unscheduled) in the 7.5 Gy arm. Antithrombin was elevated in animals between days 5 and 20 regardless of TBI dose, with the most noticeable elevation occurring during the second-week post-exposure after which values returned to normal. One animal presented with antithrombin deficiency (37.2% of normal activity) on day 7 post-exposure to 7.0 Gy (Figure 4).