Performance and reference intervals of thrombin generation test: results from the Brazilian longitudinal study of adult health (ELSA-Brasil). A cross-sectional study

ABSTRACT BACKGROUND: The thrombin generation test (TGT) has shown promise for investigation of hemorrhagic and thrombotic diseases. However, despite its potential, it still needs standardization. Moreover, few studies have established reference values for TGT parameters. In Brazil, these values have not yet been established. OBJECTIVE: To determine TGT performance and reference intervals for TGT parameters in healthy individuals. DESIGN AND SETTING: Cross-sectional study conducted among participants in the Brazilian Longitudinal Study of Adult Health (Estudo Longitudinal de Saúde do Adulto, ELSA-Brasil). METHODS: The reference sample consisted of 620 healthy individuals. The calibrated automated thrombogram (CAT) method, under low and high tissue factor (TF) conditions, was used to assess thrombin generation. Test performance was analyzed using intra and interassay coefficients of variation (CV) and reference intervals were calculated using the nonparametric method proposed by the International Federation of Clinical Chemistry and the Clinical and Laboratory Standards Institute. RESULTS: The intraassay CV ranged from 1.4% to 2.2% and the interassay CV, 6.8% to 14.7%. The reference intervals for TGT parameters under low and high TF conditions were, respectively: lagtime: 3.0-10.3 and 1.4-3.7 min; endogenous thrombin potential (ETP): 1134.6-2517.9 and 1413.6-2658.0 nM.min; normalized ETP: 0.6-1.3 and 0.7-1.4; peak: 103.2-397.7 and 256.4-479.0 nM; normalized peak: 0.3-1.3 and 0.7-1.2; and time-to-peak: 5.6-16.0 and 3.4-6.7 min. These parameters were categorized relative to sex. Conclusion: TGT performance was adequate and the proposed reference intervals were similar to those of other studies. Our findings may be useful for consolidating the TGT, through contributing to its standardization and validation.

Thrombogram: case report of pseudothrombocytopenia / Plaquetograma: relato de caso de pseudotrombocitopenia

ABSTRACT The thrombogram is one of the components of the blood count that includes platelet quantification and evaluation. The presence of laboratory artifacts, such as incorrect platelet counts by autoanalyzers, can lead to pseudothrombocytopenia, which is responsible for 15% to 30% of the cases of isolated thrombocytopenia observed in laboratory routine. Pseudothrombocytopenia induced by the anticoagulant ethylenediaminetetraacetic acid (EDTA) is one of the most frequent cases in which the presence of anticoagulant in blood samples can cause platelet aggregation or platelet satellitism. Careful observation of the data emitted by autoanalyzers, such as platelet and flag histograms, is crucial. Other procedures, such as checking for clotting in the sample, repeating the sample and viewing a peripheral blood smear, requesting a new sample taken with another type of anticoagulant, such as citrate, are imperative for the confirmation of cases of pseudothrombocytopenia.

RESUMEN El plaquetograma es uno de los componentes del hemograma que incluye la cuantificación y la evaluación de las plaquetas. La presencia de artefactos de laboratorio, como los recuentos incorrectos del número de plaquetas por los analizadores hematológicos puede originar casos de pseudotrombocitopenia (del 15% al 30% de los casos de trombocitopenias aisladas observados en la rutina del laboratorio). La pseudotrombocitopenia inducida por el anticoagulante ácido etilendiaminotetraacético (EDTA) es uno de los casos más comunes en los que la presencia de anticoagulante con muestras de sangre puede producir agregación plaquetaria o satelitismo plaquetario. La observación criteriosa de los datos emitidos por los autoanalizadores (por ejemplo, histogramas plaquetarios y alarmas) es crucial. Otros procedimientos, como la verificación de la existencia de un coágulo en la muestra, la repetición del frotis de sangre periférica, además de la solicitud de nueva muestra con otro tipo de anticoagulante, como el citrato, son importantes para confirmar casos de pseudotrombocitopenia.

RESUMO O plaquetograma é um dos componentes do hemograma que inclui a quantificação e a avaliação plaquetária. A presença de artefatos laboratoriais, como as contagens incorretas do número de plaquetas pelos analizadores hematológicos, pode originar casos de pseudotrombocitopenia (15% a 30% de casos de trombocitopenias isoladas observados na rotina laboratorial). A pseudotrombocitopenia induzida pelo anticoagulante ácido etilenodiaminotetracético (EDTA) é um dos casos mais comuns em que a presença do anticoagulante em amostras de sangue pode provocar agregação plaquetária ou satelitismo plaquetário. A observação de forma criteriosa dos dados emitidos pelos analizadores (por exemplo, histograma de plaquetas e flags) é crucial. Outros procedimentos, como a verificação da existência de coágulo na amostra, a repetição da amostra e a visualização de um esfregaço de sangue periférico, além do pedido de nova amostra colhida com outro tipo de anticoagulante, como o citrato, são importantes para confirmar casos de pseudotrombocitopenia.

Platelet profile is associated with clinical complications in patients with vivax and falciparum malaria in Colombia

Introduction Thrombocytopenia is a common complication in malaria patients. The relationship between abnormal platelet profile and clinical status in malaria patients is unclear. In low and unstable endemic regions where vivax malaria predominates, the hematologic profiles of malaria patients and their clinical utility are poorly understood. The aim of this study was to characterize the thrombograms of malaria patients from Colombia, where Plasmodium vivax infection is common, and to explore the relationship between thrombograms and clinical status. Methods Eight hundred sixty-two malaria patients were enrolled, including 533 (61.8%) patients infected with Plasmodium falciparum, 311 (36.1%) patients infected with Plasmodium vivax and 18 (2.1%) patients with mixed infections. Results The most frequently observed changes were low platelet count (PC) and high platelet distribution width (PDW), which were observed in 65% of patients; thrombocytopenia with <50,000 platelets/µL was identified in 11% of patients. Patients with complications had lower PC and plateletcrit (PT) and higher PDW values. A higher risk of thrombocytopenia was identified in patients with severe anemia, neurologic complications, pulmonary complications, liver dysfunction, renal impairment and severe hypoglycemia. The presence of thrombocytopenia (<150,000 platelets/µL) was associated with a higher probability of liver dysfunction. Conclusions Young age, longer duration of illness and higher parasitemia are associated with severe thrombocytopenia. Our study showed that thrombocytopenia is related to malaria complications, especially liver dysfunction. High PDW in patients with severe malaria may explain the mechanisms of thrombocytopenia that is common in this group of patients. .

Thrombin generation increasing with age and decreasing with use of heparin indicated by calibrated automated thrombogram conducted in Chinese / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>Calibrated Automated Thrombogram(CAT) is a test to monitor the generation of thrombin. It can be described by four parameters: lag time, peak thrombin, endogenous thrombin potential (ETP) and time to peak (ttPeak). This study aims to determine the normal ranges of CAT parameters in Chinese, and evaluate whether thrombin generation is correlated with the concentration of heparin/low molecular weight heparin.</p><p><b>METHODS</b>Plasma from 120 healthy subjects were collected to determine the normal rangea of CAT parameters in Chinese. Normal plasma pool (NPP, n=25) spiked with different concentrations of heparin or enoxaparin were used to detecte CAT parameters. The overall and age specific normal ranges of CAT parameters were calculated using descriptive statistics method with mean±2SD. The correlation between CAT parameters and age or concentrations of heparin, enoxaparin were analyzed with linear regression model.</p><p><b>RESULTS</b>The normal ranges for lag time, peak thrombin, ETP, ttPeak in the subjects were 3.648±2.465 min, 367.39±151.93 nmol/L, 2277±1030 nmol/L•min and 6.372±4.280 min respectively. Age was linearly correlated with lag time (r=-0.6583, P<0.0001), peak thrombin (r=0.4863, P<0.0001), ETP (r=0.3608, P<0.0014) and ttPeak (r=-0.6313, P<0.0001). The values of ETP/peak ratio were linearly correlated with concentrations of heparin.</p><p><b>CONCLUSION</b>The normal ranges of four CAT parameters for Chinese were determined. CAT parameters are associated with age. ETP/peak ratio could be used to monitor the process of anticoagulation therapy.</p>