[Obtaining a reference pattern of rabbit brain thromboplastin]. / La obtención de un patrón de referencia de tromboplastina de cerebro de conejo.

Thromboplastin is a tissue extract used in the prothrombin time test (PT) necessary for oral anticoagulant control. The interlaboratory variability of the results of the PT test with thromboplastins of different tissue types, besides differences due to reporting PT in seconds or percentage, indicate the need for a standardized reference thromboplastin in order to express PT results on a common scale. The aim of the present work is to encourage the laboratory hospital either singly or in regional groups, to produce a standardized thromboplastin for their own use, to insure the control of oral anticoagulant therapy. Rabbit brain thromboplastin was prepared by Quick's technique. The reagent was calibrated against the international reference thromboplastin RBT/079, following the recommendations of the World Health Organization (WHO). Statistical analyses of the data were performed using an orthogonal regression. We obtained an international sensitivity index (ISI) of 2.177, a standard error of 0.0454 and a coefficient of variation of 2.09%. An international normalized ratio (INR) was also obtained for the conversion of measured PT to a common scale. The INNSZ thromboplastin is the first national reference preparation. With this reagent the introduction of an international scale for the control of oral anticoagulant therapy has become feasible in our country.

Neutralizing antibodies against certain viruses in the sera of residents of Trinidad, B.W.I

Blood samples taken from 1,055 indigenous residents of Trinidad, B.W.I., were tested for neutralizing antibody against 17 different viral agents known or believed to be arthropod-borne, in 4,555 protection tests. Yellow fever, Ilheus and dengue are, or have, on the basis of protection tests, presumably present, widespread, and common in Trinidad. A yellow fever outbreak occurred during the course of investigations in 1954. There is no evidence that Venezuelan equine encephalitis has been present on the island since the last reported outbreak in 1943. A small number of sera were found which neutralized St. louis encephalitis virus. No interpretation of this result is attempted. Although no human sera netralized Eastern equine encephalitis virus, two different specimens of serum from one donkey neutralized the virus in two tests. Interpretation of tests against Uganda S, West Nile, Semliki, Ntaya, and Japanese B is complicated by the possibility of interfering cross-immune reactions. All tests with Bwamba, Zika, Anopheles A, Western equine encephalitis, and Bunyamwera viruses were negative. A provisional ecological zoning of the island is presented, based upon distribution of immunity against several Virus agents. (Summary).

Neutralizing antibodies against certain viruses in the sera of residents of Trinidad, B. W. I

Blood samples taken from 1,055 indigenous residents of Trinidad B. W. I., were tested for neutralizing antibody against 17 different viral agents known or believed to be arthropod-borne, in 4,555 protection tests. Yellow fever, Ilheus and dengue are, or have been, on the basis of protection tests, presumably present, widespread, and common in Trinidad. A yellow fever outbreak occurred during the course of investigation in 1954. There is no evidence that Venezuelan equine encephalitis has been present on the island since the last reported outbreak in 1943. A small number of sera were found which neutralized St Louis encephalitis virus. No interpretation of this result is attempted. Although no human sera neutralized Eastern equine encephalitis virus, two different specimens of serum from one donkey neutralized the virus in two different tests. Interpretation of tests against Uganda S, West Nile, Semliki, Ntaya, and Japanese B is complicated by the possibility of interfering cross-immune reactions. All tests with Bwamba, Zika, Anopheles A, Western equine encephalites, and Bunyamwere viruses were negative. A provisional ecological zoning of the island is presented, based upon distribution of immunity against several viral agents (Summary)