ABSTRACT
Objetivo: Analisar os testes de coagulação: tempo de protrombina (TP) e tempo de tromboplastina parcial (TTP) em diferentes tempos de centrifugação da amostra da biológica, com relação ao protocolo padrão do Clinical Laboratory Standards Institute (CLSI). Métodos: As amostras foram divididas em cinco alíquotas de 1 mL. Foi realizada a centrifugação em 15, 10, 5, 2 e 1 minuto, com velocidade de 1500 g. O TP e TTP foram imediatamente analisados em aparelho automatizado. Os plasmas foram analisados para presença de elementos residuais: eritrócitos, leucócitos e plaquetas. Resultados: Observou-se alteração dos valores do TP nos tempos de centrifugação 10, 5, 2 e 1 minuto e do TTP em 5, 2 e 1 minuto, com relação ao protocolo padrão. Na interpretação de Bland Altman, observou-se um viés significativo do limite clínico aceitável para o TP e para o TTP em todos os tempos de centrifugação, com relação ao protocolo padrão. Apenas no tempo de centrifugação de 15 minutos não foram encontradas células residuais nas amostras analisadas. Conclusão: O tempo de centrifugação de 15 minutos é o ideal para remoção completa das células sanguíneas residuais e para garantia da confiabilidade dos resultados dos testes de coagulação TP e TTP.
Objective: To analyze the coagulation tests: prothrombin test (PT) and partial thromboplastin time (PTT) in different centrifugation times of the sample, in relation to the standard protocol of the Clinical Laboratory Standards Institute (CLSI). Methods: The selected samples were splitted up into five aliquots of 1 mL. Centrifugation of these aliquots was carried out at 15, 10, 5, 2 and 1 minute at 1500 g. The PT and PTT were analyzed in an automated apparatus. The plasmas were analyzed for presence of residual elements: erythrocytes, leukocytes and platelets. Results: The results showed a change in the values of PT at the 10, 5, 2 and 1 minute centrifugation times and the PTT at 5, 2 and 1 minutes, relative to the standard protocol. In the interpretation of Bland Altman, a significant bias of the acceptable clinical limit for TP and TTP at all centrifugation times was observed, relative to the standard protocol. Only in the 15 minute centrifugation time no residual cells were found in the analyzed samples. Conclusion: The present study demonstrated that the 15-minute centrifugation time is ideal for complete removal of residual blood cells and to ensure the reliability of the results of the PT and PTT coagulation
Subject(s)
Humans , Male , Female , Prothrombin Time , Blood Coagulation Tests , CentrifugationABSTRACT
BACKGROUND: To evaluate the usefulness of preoperative screening for coagulation disorders in children who have undergone surgery. METHODS: From January 2003 to December 2005, we prospectively evaluated laboratory and bleeding histories in 1,911 children between the ages of one year and 15 years. All of the patients had preoperative coagulation screening with a measurement of complete blood count, prothrombin time and activated partial thromboplastin time. The sensitivity, specificity and positive and negative predictive values following a preoperative coagulation-screening test were evaluated by a comparison of the type of surgery and bleeding complications that occurred during and after surgery. RESULTS: There were no patients with previously proven coagulopathies or suspicious medical histories. Among the 1,911 cases, a subset of 22 patients had persistent abnormalities detected after laboratory testing. In two of the 22 patients, lupus anticoagulant was detected and in one of the 22 patients, a factor VIII deficiency was discovered. There were 46 patients that had postoperative bleeding and required hospitalization extension or readmission for stanching. Among the 46 patients, 44 patients demonstrated normal coagulation after testing and two patients demonstrated abnormal coagulation after testing. Following a preoperative coagulation-screening test, a low sensitivity (0.04) and positive predictive value (0.09) were determined. CONCLUSION: For the prediction of perioperative bleeding, the use of a coagulation-screeningtest showed a very low positive predictive value. Many false positive laboratory tests coupled with the relative rarity of inherited and acquired coagulopathies raises doubt about the overall value of routine preoperative coagulation screening in children.