Jornal Vascular Brasileiro
Jornal Vascular Brasileiro
Original Article

Comparison between the conventional method and a portable device for determination of INR

Determinação do INR: comparação entre método convencional e dispositivo portátil

André Camacho Oliveira Araújo; Rodrigo Borges Domingues; Bonno van Bellen

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CONTEXT:Anticoagulation with warfarin is considered the appropriate treatment for venous thromboembolism and other thrombotic pathologies. Regular INR control is required for dosage adjustment and therapeutic control. Use of portable monitoring systems optimizes management of these patients.OBJECTIVE: To compare INR measurements taken using the portable Coaguchek XS system in capillary blood with the standard laboratory method using venous blood.METHOD: Fifty-two samples each of venous and capillary blood were collected from nineteen patients on warfarin, who had been admitted to the Hospital da Beneficência Portuguesa de São Paulo, and analyzed using the conventional method and the Coaguchek XS system, respectively.RESULTS: Spearman's correlation coefficient ® for the overall performance of the two methods was 0.978 (p<0.0001; 95%CI 0.961-0.988). The Kappa measure of agreement for all patients was 76.8% (p<0.001; IC: 95% 0.975-0.561). Mean INR according to the Coaguchek XS system underestimated the values provided by the conventional method by -0.01 INR points, with a standard error of 0.342. Results for INR values greater than 3.5 were satisfactory with a correlation coefficient of 0.71, but without statistical significance (p>0.714).CONCLUSIONS: The Coaguchek XS system can be used to monitor prothrombin time in patients on oral anticoagulants, provided INR values greater than 3.5 are confirmed using the conventional laboratory method.


prothrombin time, blood coagulation, warfarin, venous thromboembolism


CONTEXTO: Anticoagulação por varfarina (warfarin) é considerada tratamento adequado para tromboembolismo venoso e outras patologias trombóticas. Deve ser realizada a mensuração do Índice Internacional Normalizado (INR) para ajuste de dosagem de medicamento para manutenção dos pacientes na faixa terapêutica. O uso de dispositivos portáteis otimiza o controle desses pacientes.OBJETIVO: Comparar as medidas do INR realizadas pelo sistema portátil Coaguchek XS, em sangue capilar, com o método laboratorial padrão em sangue venoso.MÉTODO: Dezenove pacientes em uso de varfarina, internados no Hospital da Beneficência Portuguesa de São Paulo, foram submetidos à coleta de 52 amostras analisadas pelo método convencional e coleta de sangue capilar para medida com o sistema Coaguchek XS.RESULTADOS: O coeficiente de correlação (r) de Spearman por meio da comparação de desempenho global entre os dois métodos foi de 0,978 (p<0,0001; IC: 95% 0,961-0,988). O percentual de concordância Kappa para todas as faixas foi de 76,8% (p<0,001; IC: 95% 0,975-0,561). O INR médio do sistema Coaguchek XS subestimou os valores obtidos em -0,01 pontos de INR, quando comparado ao método convencional, com erro padrão de 0,342. Valores acima de 3,5 mostraram resultados satisfatórios com coeficiente de correlação de 0,71, mas sem significância estatística (p>0,714).CONCLUSÕES: O sistema Coaguchek XS pode ser utilizado na monitorização do tempo de protrombina em pacientes com uso de anticoagulantes orais, desde que valores de INR acima de 3,5 sejam confirmados por meio de medidas realizadas em laboratório convencional.


tempo de protrombina, coagulação sanguínea, varfarina, tromboembolismo venoso


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