IntroductionInterference on biological assays due to hemolysis, icterus, or lipemia (HIL) could represent a significant source of analytical errors leading to inaccurate interpretation of results. The aim of this study was to assess the HIL interference on prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen, using mechanical and optical detection methods.MethodsControl plasmas and plasmas from patients treated with vitamin K antagonists or unfractionated heparin, with or without HIL, were performed on two analytical detection systems in order to identify potential analytical biases. Whether HIL lead to significant biological interferences was also evaluated, and a cutoff point for HIL‐induced analytical bias was determined.ResultsHemolysis influenced PT and aPTT when hemoglobin was at 5 and 1.5 g/L in plasma, respectively. At 1.8 g/L, a positive relationship was found between the bias and the hemoglobin supernatant level only for fibrinogen measurement, using optical detection. For icteric interference, no significant bias was observed until a bilirubin concentration of 30 mg/dL. Lipamia (>500 mg/dL) led to analytical interference when using the optical analyzer.ConclusionThe present study detected analytical interferences such as lipemia (>500 mg/dL) on coagulation tests on the optical analyzer. We also found a biological impact on the results in case of hemolyzed sample: Fibrinogen was decreased when the hemoglobin level was superior to 1.8 g/L, PT was prolonged beyond 5 g/L, and aPTT was shortened beyond 1.5 g/L hemoglobin concentration, especially in patients treated with heparin. Above these thresholds, it is important not to give results that could influence the clinical decision.
Introduction: The correct diagnosis and classification of VWD (von Willebrand dis-
Congenital factor XIII (FXIII) deficiency is one of the rarest coagulation factor deficiencies; the estimated prevalence is 1 in 2-5 million. FXIII has a tetrameric structure with two subunits, A and B.After activation, FXIII increases the resistance of clots but also possibly plays many other roles, notably in angiogenesis and maintaining pregnancy. Severe inherited FXIII deficiency is defined as a plasma level lower than 5 IU/dL and can affect the A or the B subunit. 1 The clinical characteristics are neonatal umbilical haemorrhage (80% of cases) and spontaneous intracranial haemorrhage (30% of cases); it can also be revealed by induced bleeding, delayed healing and repeated miscarriages. 2 To prevent the high risk of intracranial haemorrhage, prophylactic therapy with FXIII concentrates (FXIII) may be prescribed. 3The standard coagulation tests are insensitive to FXIII deficiency, which can only be diagnosed using specific assays. However, the widely used chromogenic method for the measurement of plasma FXIII activity has restricted linearity and lacks accuracy for low FXIII levels (<10 IU/dL), and enzyme-linked immunosorbent assay (ELISA) methods do not entirely reflect the plasma activity of FXIII. 4 This affects both diagnosis and therapeutic management.Thromboelastometry/ROTEM ® (Instrumentation Laboratory) is a global haemostasis assay measuring viscoelastic changes associated with fibrin polymerization and seems to provide more precise coagulation efficiency results for FXIII activities < 10 IU/dL. 5 ROTEM uses ellagic acid (INTEM test) or tissue factor (EXTEM test) for coagulation activation. In addition, in the FIBTEM test, cytochalasin D can be added to the EXTEM test reagents to inhibit the platelet contribution to the clot to isolate the contribution of fibrin/fibrinogen and FXIII. Among the ROTEM parameters measured, such as clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), % reduction in the MCF 60 minutes after the CT (LI60), and maximum lysis (ML), the FXIII deficiency could give reduced clot strength (MCF) and impaired clot stability (increased ML or reduced LI60). 5,6 In the present letter, we briefly report 3 cases for which we used thromboelastometry to monitor the effectiveness of the plasma-derived FXIII (pdFXIII) infusions in patients with severe congenital FXIII deficiency. The normalization of LI60 (reference range: 88%-96%) or the MCF (reference range: 50-72 mm) using the EXTEM assay were the criteria retained to modify the interval and/or the concentration of the pdFXIII doses.Case 1 was a girl in whom severe FXIII deficiency was diagnosed at 19 months of age following the fourth episode of intracerebral haemorrhage or subdural haematoma. Measurement of FXIII < 10 IU/dL led to the diagnosis of severe FXIII deficiency. The last haematoma was treated with 25 IU/kg/week pdFXIII for 1 month, which was then reduced to 25 IU/kg every 4 weeks, with the objective to maintain long-term prophylaxis (LTP) with the residual FXIII activity > 10 IU/ dL. Three months after ...
Introduction The accurate diagnosis of heparin‐induced thrombocytopenia (HIT) is essential to ensure adequate treatment and prevent complications. First step diagnosis test are immunoassays including enzyme‐linked immunosorbent assays (ELISAs) and rapid immunoassays. Methods Using a Bayesian approach, we prospectively evaluated the performance of the IgG PF4/polyvinylsulfonate ELISA and a chemiluminescent immunoassay (CLIA), which are specific for IgG and use the same antigenic target to detect HIT antibodies. Results One hundred and eighty‐four 184 consecutive patients with an intermediate (n = 159) or high (n = 25) clinical pretest probability of HIT based on the 4Ts score or platelet pattern were included. Both immunoassays (IAs) were performed on all 184 samples, and definite HIT was confirmed with a positive serotonin release assay in 29 patients (12.7%). The sensitivity (Ss) and negative predictive value (NPV) of ELISA were excellent (100%) allowing HIT to be excluded with good confidence when the test was negative. In addition, the Ss and NPV of the CLIA equalled 93.1% and 98.6%, respectively, as it was negative in two definite HIT. When the CLIA was negative, the post‐test probability of HIT was 0.7% in case of intermediate risk. Although there was excellent agreement between CLIA and ELISA results, the quantitative values provided by the two IAs were not correlated. Conclusion AcuStar HIT® detects more than 90% of HIT, as do all rapid IAs, and appears to be a good tool for excluding HIT when the pretest probability is intermediate. A chemiluminescent signal higher than 10 IU/mL is highly predictive of definite HIT with a PPV of 100%.
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