Fases pré-analítica, analítica e pós-analítica no monitoramento laboratorial da anticoagulação com antagonistas da vitamina K / Pre-analytical, analytical, and post-analytical phases in laboratory monitoring of anticoagulant therapy with vitamin K antagonists

A trombose é uma doença caracterizada por eventos de hipercoagulabilidade. A terapêutica anticoagulante oral com antagonistas da vitamina K (AVKs) é amplamente indicada para prevenção e/ou controle de distúrbios da coagulação. O manuseio de administração dos AVKs é difícil devido à complexidade da definição da dose. Em geral, o monitoramento de indivíduos submetidos à terapêutica com AVK é realizado pela determinação do tempo de protrombina, em que se avalia o grau de anticoagulação através do coeficiente internacional normatizado. Invariavelmente, o fluxo do processamento laboratorial, que compreende as fases pré-analítica, analítica e pós-analítica, é importante para a fidedignidade dos resultados, repercutindo na conduta médica de forma determinante. O objetivo deste estudo foi a realização de uma revisão da literatura científica descritiva utilizando bases de dados eletrônicos para busca de materiais científicos, como Google Scholar, MEDLINE, LILACS, PubMed, SciELO e Science Direct. Abordamos alguns aspectos relacionados ao fluxo analítico da monitoração laboratorial em um laboratório de análises clínicas. Em conclusão, é necessária uma apropriada condução das fases analíticas para que seja possível o sucesso terapêutico com uso dos AVKs (AU)

Thrombosis is a disease characterized by hypercoagulable events. Oral anticoagulant therapy with vitamin K antagonists (VKAs) is widely indicated for prevention and/or control of coagulation disorders. The administration of VKAs is difficult because of the complexity of dose setting. In general, individuals submitted to VKA therapy are monitored by prothrombin time, in which the degree of anticoagulation is assessed by the international normalized ratio. Invariably, the flow of laboratory processing, which comprises pre-analytical, analytical, and post-analytical phases, is of importance to the trustworthiness of results, with significant consequences to the medical practice. The purpose of this study was to carry out a review of the scientific literature using electronic databases to search for scientific materials, such as Google Scholar, MEDLINE, LILACS, PubMed, SciELO, and Science Direct. We discuss some aspects related to the analytical flow of laboratory monitoring in a clinical laboratory. In conclusion, appropriate management of the analytical phases is necessary so that therapeutic success using VKAs is possible (AU)

Determinación de valores de referencia para pruebas de coagulación en una población pediátrica / Determination of reference ranges for coagulation tests in a pediatric population / Determinação dos valores de referência para provas de coagulação numa população pediátrica

El sistema hemostático varía a lo largo de las primeras etapas de vida ya que el organismo sufre un proceso dinámico de cambios durante el período de crecimiento. En la literatura existen pocos trabajos sobre valores de referencia en niños de pruebas de hemostasia y por ello la importancia de investigar en el tema. El presente es un trabajo retrospectivo que se realizó sobre 512 niños hasta 17 años que concurrieron al hospital con pedido médico de estudio prequirúrgico para cirugías programadas ambulatorias de los cuales se obtuvieron, de sus historias clínicas, los valores de actividad protrombínica del plasma (APP), tiempo de tromboplastina parcialmente activada (aPTT) y fibrinógeno. Los resultados, teniendo en cuenta el percentilo 97,5, mostraron diferencias significativas para la determinación del APP y del aPTT, no observándose diferencias en la prueba del fibrinógeno. Es importante que cada laboratorio establezca sus propios valores de referencia para estas pruebas, ya que no son extrapolables a los de los adultos. En este estudio se demuestra que el sistema hemostático sufre modificaciones durante la infancia que deben ser tenidas en cuenta para interpretar correctamente los resultados de las pruebas realizadas.

The haemostatic system varies throughout the first stages of life since the body undergoes a dynamic process of changes during the growth period. Little research has been conducted on the reference ranges of haemostasis tests in children; therefore, it is of great significance to investigate this subject. The following study is retrospective and it was conducted on 512 children up to 17 years old that attended the hospital requesting presurgical testing for scheduled ambulatory surgeries. Ranges of plasma prothrombin activity (APP), the activated partial thromboplastin time (aPTT) and fibrinogen were obtained from the patients' medical records. Taking into account the 97.5 percentile, the results showed important differences in APP and aPTT determination but showed no differences in the fibrinogen test. It is important that all laboratories establish their own reference ranges for these tests since they cannot be extrapolated to the ones in adults. This study proves that the haemostatic system undergoes significant changes during infancy which shall be taken into account for the correct interpretation of the results of the tests carried out.

O sistema hemostático varia ao longo das primeiras etapas da vida visto que o organismo sofre um processo dinâmico de alterações durante o periodo de crescimento. Na literatura existem poucos estudos sobre valores de referência de testes de hemostasia em crianças e é por esse motivo que é importante pesquisar sobre o assunto. O presente trabalho é retrospectivo e foi realizado em 512 crianças de até 17 anos que assistiram ao hospital com pedido médico de exame pré-cirúrgico para cirurgias ambulatoriais programadas, de cujos prontuários foram obtidos os valores da atividade protrombínica (APP), tempo de tromboplastina parcialmente ativada (aPTT) e fibrinogênio. Os resultados, levando em consideração o percentil 97,5, mostraram diferenças significativas para a determinação do APP e do aPTT, não encontrando diferenças no teste do fibrinogênio. É importante que cada laboratório estabeleça seus próprios valores de referência para estes testes, visto que não se pode extrapolar para os adultos. Neste estudo é demonstrado que o sistema hemostático sofre modificações na infância as quais devem ser consideradas para interpretar corretamente os resultados dos testes realizados.

A survey of coagulation laboratory practice in Thailand: the first step to establish a National External Quality Assessment Scheme (NEQAS) for blood coagulation.

BACKGROUND: External quality assessment (EQA) is an essential component of laboratory quality assurance. In Thailand, there is no EQA program for coagulation tests at the national level. OBJECTIVE: To collect the necessary data in the first step to set up a National External Quality Assessment Scheme (NEQAS) and to assess the status of coagulation laboratory practice in Thailand. MATERIAL AND METHOD: Questionnaires were sent to hospitals to obtain information about the hospitals, their coagulation laboratory practice and EQA. RESULTS: From a dispatch of 220 questionnaires, 124 (56.4%) were returned. Of the 112 hospitals that had coagulation tests, all of them performed prothrombin time (PT), and 110 laboratories performed activated partial thromboplastin time (APTT) as well. Thirty eight percent of laboratories still used 3.8% sodium citrate as the anticoagulant for coagulation tests. The majority of laboratories (65%) reported normal control value with the patient results. Only 42% of coagulation laboratories established their own reference range. The denominators of PT ratio and APTT ratio calculations were derived from several sources apart from the mean of normal subjects. Seven of 112 (6%) laboratories participated in an EQA program. CONCLUSION: The present survey represents an overview of the current laboratory practice for coagulation tests in Thailand Improvement is necessary, and the survey results emphasize the need for establishing an EQA program in Thailand

Quality control and quality assessment of coagulation tests in Japan.

We have used prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (Fbg), and fibronogen/fibrin degradation products (FDP) as screening coagulation tests, and antithrombin III (AT III), plasminogen (Plg), alpha2-plasmin inhibitor (alpha2-PI), protein C (PC), thrombin-AT III complex (TAT), plasmin-alpha2-PI complex (PIC), and D-dimer as special coagulation tests. We report the present condition of internal and external quality control for these coagulation tests in Japan. We made a summary report of internal quality control of some coagulation tests in Division of Hematology Laboratory, Department of Laboratory Medicine, Hokkaido University Hospital. The repeatability and reproducibility of screening tests were good, but those of special tests were partly adequate. We have participated in some external quality control surveillance including Japan Medical Association (JMA), Japanese Association of Laboratory Medical Technologists (JALMT), College of American Pathologists (CAP), and some commercial quality control surveillance. We also reported the results of some external quality control surveillance.

Application of indicators for quality improvement in the coagulation laboratory.

Indicators are tools that measure work performance and serve as a guide to improve the quality of laboratories. Seven Indicators for quality improvement have been established in our coagulation laboratory. They are :- 1). percentage of pre-analytical problems, 2). personnel competency scores, 3). results of external quality assessment, 4). % coefficient of variation (CV) of control materials, 5). unit cost, 6). percentage of reports within determined time, and 7). percentage of customers who were satisfied. The percentage of preanalytical error gradually decreased from 1.8% in April 2001 to 0.8% in June 2001 as a result of co-operation between the coagulation laboratory and the wards. Since there is no system to check personnel competency at a national level in Thailand, we set up a program for testing personnel competency in our department by asking every technician to take a written and practical laboratory examination. The scores achieved by our personnel ranged from 40 to 90%. For those who achieved scores of lower than 70%, we limited their responsibilities and organized a training program for them. In order to check our laboratory's accuracy, we are enrolled in the WHO International External Quality Assessment Scheme (IEQAS) in Blood Coagulation and have been since 1987. The survey results indicated that most of our laboratory tests were within consensus including our homemade ELISA tests for protein C, protein S and vWF antigen. The percent CVs of control materials used for the internal daily control for every test were analyzed. They ranged from 2.3 for normal APTT to 11.4 for the low level of free protein S in plasma. The unit cost for each test was analyzed to determine the cost-effectiveness of the laboratory. We set the goal for the turn around time for emergency coagulation tests to be within an hour and the percentage of reports within this time was 91.6% in August 2001. The last indicator was the percentage of satisfied customers, which gave an indication of the quality of all Out Patient Department (OPD) services performed by our department. We sent 400 questionnaires to doctors, nurses and patients in OPD asking their opinion of both the technical services and the behavior of our technicians. The percentage satisfaction of our customers concerning services offered to OPD was lower than 50%. We plan to improve the last 2 indicators by expanding the space of the OPD/emergency laboratory and reorganizing the service system. All indicators mentioned above have helped to improve the quality of our laboratory greatly.

External quality assessment scheme for blood coagulation.

The aim of setting an External Quality Assessment Scheme (EQAS) for Blood Coagulation is to achieve a harmonization among the participating laboratories on blood coagulation testing. In Indonesia EQAS for blood coagulation is organized by the Department of Clinical Pathology, Faculty of Medicine, University of Indonesia which cooperates with the Indonesian Society of Clinical Pathologists, Jakarta Chapter. Currently coagulation tests in Indonesia are only performed in a limited number of laboratories especially in the hospital. Therefore only 65 laboratories participated in the first trial of EQAS. The control material for EQAS was provided by Organon Teknika and parameters involved in the first trial were PT, INR, APTT, and fibrinogen. Currently there are 7 brands of reagents for coagulation tests available in the market, i.e.: Behring, Biomerieux, Biopool, Human, Nycomed, Organon, and Ortho. In the evaluation, the results of each participant were compared to the median of participants who used the same reagent. If the number of participants using a given reagent was less than 10, then the result of each participant was compared to the median of overall participants. The result of a given parameter was classified as within consensus if it fell into the range of median +/- 15%. In the overall evaluation, the percentage of participants which was classified as within consensus for PT, INR, APTT, and fibrinogen were 68%, 64%, 63%, and 67%, respectively, but the CV for PT, INR, APTT, and fibrinogen were 19.84%, 17.89%, 20.21%, and 23.96% respectively. In the evaluation of participating laboratories using Behring's reagent, the percentages of participants classified as within consensus for PT, INR, APTT, and fibrinogen were 72%, 82%, 54%, and 74%, respectively. For Organon's product users, the percentages of those parameters were 84.6%-90%, 48%-75%, 86%, and 67%, respectively. It is concluded that around two-thirds of overall participating laboratories achieved harmonization in the results of coagulation test, but the variation of all parameters is still wide.

Aspectos del aseguramiento de la calidad en los laboratorios de hemostasia / Quality assurance in hemostasia laboratories

En concepto de control de la calidad se ha expandido en los últimos años y actualmente se está sustituyendo por el término de garantía de la calidad como concepto más abarcador, que comprende todo el proceso de la actividad relacionada con el laboratorio clínico, desde que se genera la petición analítica hasta que el resultado llega a manos del solicitante. Estas prácticas se requieren para la acreditación de los laboratorios clínicos y servicios de transfusión, en la que la palabra clave es la documentación de los sistemas de aseguramiento de la calidad. En la hemostasia, la etapa pre-analítica es una etapa fundamental; de ella depende en gran medida el resultado final, la preparación adecuada de controles, así como el uso de calibradores para la determinación de la actividad de los factores individuales y la detección de inhibidores. La determinación del tiempo de protrombina (TP), de la relación normalizada internacional y del tiempo parcial de tromboplastina activado (TPTA), son determinaciones usuales en el control externo de la calidad (CEC), mientras que la determinación de la concentración de fibrinógeno, factor VIII coagulante, otros factores e inhibidores fisiológicos de la coagulación, se incluyen de forma más esporádica. Actualmente se están llevando a cabo programas internacionales para la estandarización de varias pruebas de laboratorio. Para implementar la estandarización de las pruebas y materiales usados en la hemostasia, varias instituciones han decidido dirigir sus esfuerzos para lograr sistemas comunes de referencia.

Pruebas de coagulación

Los trastornos de la hemostasia vienen siendo un foco de interés durante los últimos años debido al progreso en el conocimiento y la comprención de algunas patologías que causan hemorragias o trombosis. Para un diagnóstico correcto y un tratamiento eficaz de las enfermedades trombóticas o hemorrágicas es necesaria una adecuada historia clínica del paciente; pero más importante aún, un laboratorio que garantice un estricto control de calidad en las pruebas de coagulación. En este módulo se revisarán las principales pruebas de laboratorio de coagulación disponibles en el medio, que ayudan al clínico a realizar un diagnóstico apropiado mediante la identificación del componente de la hemostasia que con mayor posibilidad está alterado o deficiente.

Técnicas diagnósticas de laboratorio en trombofilias congénitas / Diagnostic laboratory techniques for hereditary trombophillias

Las alteraciones hereditarias de los inhibidores naturales de la coagulación y de los componentes del sistema fibrinolítico, están asociadas con enfermedad tromboembólica. Como no siempre es posible determinar la causa de la trombofilia, se analizan aquí distintas metodologías que pueden ser de utilidad para arrojar más luz sobre este problema; y que están disponibles en la bibliografía, para medir la actividad funcional y la concentración de antitrombina III, proteína C, proteína S, cofactor II de la heparina, glicoproteína rica en histidina, lipoproteína A, fibrinógeno, plasminógeno y homocisteína. En todos los casos es conveniente comenzar primero con la determinación de la actividad funcional de la proteína en estudio y, en caso de encontrar una alteración, se completará el estudio con una cuantificación inmunológica u otra metodología que permita obtener mayor información sobre la alteración