Sistema internacional de la OMS para evaluar la calidad de las pruebas detectoras de anticuerpos contra el VIH: resultados de la segunda distribución de sueros / WHO international quality assessment scheme for HIV antibody testing: results from the second distribution of sera

El sistema internacional de la OMS para evaluar la calidad de las pruebas detectoras de anticuerpos contra el virus de la inmunodeficiencia humana (VIH) se estableció para controlar la calidad de la labor desempeñada por los laboratorios en este campo. Después de la distribución de unos cuantos especímenes con fines experimentales a comienzos de 1989, una segunda distribución se hizo en febrero de 1990. En total se enviaron 20 especímenes de suero, 10 con anticuerpos contra el VIH-1, a 103 laboratorios en las seis regiones de la OMS. Se pidió a los participantes que aplicaran a los especímenes sus pruebas estandarizadas y que para cada uno notificaran a la OMS los resultados obtenidos con cada tipo de prueba diagnóstica y su interpretación con respecto ala presencia o ausencia de anticuerpos contra el VIH. En lo concerniente a los especímenes con anticuerpos, los resultados se consideraron positivos en 98,2 por ciento de los casos e indeterminados en 1,8 por ciento; no se notificaron resultados negativos falsos. En el caso de los especímenes sin anticuerpos, 90,3 por ciento de los resultados se consideraron negativos, 1,3 por ciento positivos y 8,4 por ciento indeterminados. La mayor parte de los informes con resultados indeterminados correspondieron a un espécimen en particular. Se uso una amplia variedad de pruebas diagnósticas solas y combinadas. Si se tienen en cuenta los resultados técnicos, más que su interpretación, la confiabilidad de las pruebas fue muy buena en lo que respecta a los especímenes positivos: 99,5 por ciento de los resultados registrados fueron positivos, 0,17 por ciento negativos y 0,34 por ciento indeterminados. Los especímenes negativos se asociaron con un mayor número de errores: 93,5 por ciento de los resultados registrados fueron negativos, 3,5 positivos y 3 por ciento indeterminados. Sin embargo, 61 por ciento de los resultados positivos falsos e indeterminados que se obtuvieron al aplicar las pruebas a especímenes negativos correspondieron a dos especímenes solamente. La prueba western blot dio resultados muy variados, a los que se aplicaron distintos criterios de interpretación

Sistema internacional de la OMS para evaluar la calidad de las pruebas detectoras de anticuerpos contra el VIH: resultados de la segunda distribución de sueros / WHO international quality assessment scheme for HIV antibody testing: results from the second distribution of sera

El sistema internacional de la OMS para evaluar la calidad de las pruebas detectoras de anticuerpos contra el virus de la inmunodeficiencia humana (VIH) se estableció para controlar la calidad de la labor desempeñada por los laboratorios en este campo. Después de la distribución de unos cuantos especímenes con fines experimentales a comienzos de 1989, una segunda distribución se hizo en febrero de 1990. En total se enviaron 20 especímenes de suero, 10 con anticuerpos contra el VIH-1, a 103 laboratorios en las seis regiones de la OMS. Se pidió a los participantes que aplicaran a los especímenes sus pruebas estandarizadas y que para cada uno notificaran a la OMS los resultados obtenidos con cada tipo de prueba diagnóstica y su interpretación con respecto ala presencia o ausencia de anticuerpos contra el VIH. En lo concerniente a los especímenes con anticuerpos, los resultados se consideraron positivos en 98,2 por ciento de los casos e indeterminados en 1,8 por ciento; no se notificaron resultados negativos falsos. En el caso de los especímenes sin anticuerpos, 90,3 por ciento de los resultados se consideraron negativos, 1,3 por ciento positivos y 8,4 por ciento indeterminados. La mayor parte de los informes con resultados indeterminados correspondieron a un espécimen en particular. Se uso una amplia variedad de pruebas diagnósticas solas y combinadas. Si se tienen en cuenta los resultados técnicos, más que su interpretación, la confiabilidad de las pruebas fue muy buena en lo que respecta a los especímenes positivos: 99,5 por ciento de los resultados registrados fueron positivos, 0,17 por ciento negativos y 0,34 por ciento indeterminados. Los especímenes negativos se asociaron con un mayor número de errores: 93,5 por ciento de los resultados registrados fueron negativos, 3,5 positivos y 3 por ciento indeterminados. Sin embargo, 61 por ciento de los resultados positivos falsos e indeterminados que se obtuvieron al aplicar las pruebas a especímenes negativos correspondieron a dos especímenes solamente. La prueba western blot dio resultados muy variados, a los que se aplicaron distintos criterios de interpretación

Publicado en inglés en el Bull. Pan Am. Health Organ. 70(5), 1992

WHO international quality assessment scheme for HIV antibody testing: results from the second distribution of sera.

The WHO international quality assessment scheme for human immunodeficiency virus (HIV) antibody testing has been established to monitor the quality of laboratory performance in testing for antibodies to HIV. Following a small trial distribution of specimens early in 1989, the second distribution was made in February 1990. A total of 20 specimens of sera, 10 of which contained antibodies to HIV-1, were sent to 103 laboratories located in the six WHO Regions. Participants were asked to test the specimens using their routine methods and to report to WHO their findings on each specimen for each diagnostic assay used and their interpretation of the HIV antibody status of each specimen. For the antibody-positive specimens, 98.2% of the results were interpreted as positive and 1.8% as indeterminate; no false-negative interpretations were reported. For the antibody-negative specimens, 90.3% of the results were interpreted as negative, 1.3% as positive, and 8.4% as indeterminate. Most of the indeterminate reports were associated with one particular specimen. A wide variety of diagnostic assays and combinations of assays were used. In terms of the technical results obtained rather than their interpretation, the assays appeared extremely reliable for the positive specimens, with 99.5% of assay results being recorded as positive, 0.17% as negative, and 0.34% as indeterminate.(ABSTRACT TRUNCATED AT 250 WORDS)

World Health Organization quality assessment programme on HIV testing.

A serum panel comprising 19 samples of known (five positives and 14 negatives) but undisclosed HIV-1-antibody content was distributed to 30 national reference laboratories for HIV serology. In order to simulate normal circumstances of referral, participants were asked to test the panel for HIV-1-antibody status using their normal procedures. Results of testing were returned by 28 participants. There were great variations in the number and combinations of tests used. The number used ranged from one to five assays per laboratory and none of the 24 laboratories using two or more tests employed the same combination. A high average success rate of 99% was seen with the positive samples. More errors occurred with the negative samples, with an average of 87% correct negative reports. Only four of the 14 negative specimens were reported as negative by all participants.

Medicion de los anticuerpos contra el virus de la inmunodeficiencia humana: estudio internacional en colaboración para evaluar los sueros de referencia de la OMS

Two preparations of human sera, one reactive against human immunodeficiency virus (HIV) and the other unreactive, were evaluated as potential international reference reagents (IRR) in an international collaborative study. Twenty-one laboratories participated and tested these and five other human sera which were found to range from highly reactive to unreactive. The proposed "positive" IRR was found to react strongly in all immunoassays and gave all the expected bands in immunoblot systems using HTLV-III, LAV-I or similar virus strains as antigens. The "unreactive" serum was judged to be negative by ELISA and immunoblots. The end-points determined by ELISAs varied considerably between laboratories, even between those using the same commercial kit. This variation was reduced somewhat when the reactivities of the samples were expressed relative to the proposed IRR

Measurement of antibodies to human immunodeficiency virus: an international collaborative study to evaluate WHO reference sera.

PIP: 21 laboratories participated in an international collaborative study to evaluate potential international reference reagents for measurement of antibodies to human immunodeficiency virus (HIV). Given inherent differences between the principles of currently used assays (based on enzyme-linked or radioimmunosorbance, immunofluorescence, immunoblotting, or immunoprecipitation) and batch-to-batch variations in the preparations of reagents and kits, there is an urgent need for well-characterized reference materials that can be used to define the reliability and sensitivity of the tests, for quality control of batches, and as common references between laboratories. The 7 human sera tested included 1 reactive against HIV and 1 unreactive. The study was designed to identify the coded preparations that reacted with HIV antibodies and to ascertain the minimum amount of the reactive samples that could be detected in the methods routinely used by the participants. Participants carried out single or duplicate assays for individual manufacturer's ELISAs or by their local methods. The proposed positive international reference reagent (coded A) reacted strongly in all immunoassays and gave all the expected bands in immunoblot systems using HIV-related virus strains as antigens. The unreactive serum (coded E) was negative by ELISA and immunoblots. Although the end-points determined by ELISAs varied considerably between laboratories, even when the same commercial kit was used, this variation was reduced somewhat when the reactivities of the samples were expressed relative to preparation A. It is concluded that the proposed international reference reagent A may have value as a qualitative check on the specificity of assays, in calibrating positive controls included in kits and other assays in arbitrary units, in calibrating detection limits in arbitrary units, and for calibrating immunoblots, especially for defining the optimal amounts of antigen and determining the relative mobilities of the major HIV peptides and glycopeptides.^ieng

Report of a joint DMRQC/Organon field trial to detect hepatitis A IgM by ELISA.

The results of a field trial of a joint DMRQC/Organon ELISA kit for the detection of hepatitis A IgM antibody are reported. The participating laboratories were asked to use the kit to test a panel of 360 specimens consisting of duplicate coded samples of 180 sera. The panel was also tested by MACRIA in the Virus Reference Laboratory, Colindale. The ELISA was shown to be specific and sensitive giving good discrimination between acute and late convalescent hepatitis A sera. It was proposed that the same cut-off control as is used in the RIA (equivalent to 10 RIA units) should be adopted for the ELISA also.

Enzyme-linked immunosorbent assay (ELISA) for the detection of hepatitis Be antigen and antibody: report of a field trial.

A field trial of an enzyme-linked immunosorbent assay (ELISA) for the detection of the hepatitis Be markers is reported. It is simple to perform, is designed to be read by eye and does not require any expensive apparatus. When compared with a commercially available RIA kit for the detection of the same markers, ELISA was shown to be as sensitive as RIA for the detection of anti-HBe but slightly less sensitive for the detection of HBeAg. However if all specimens negative for both HBeAg and anti-HBe by ELISA are considered to be potentially infectious, the ELISA should prove to be as useful as RIA for determining the "e" status of HBsAg-positive patients and, therefore, provide a reliable indication of the risk of secondary spread of hepatitis B infection to contacts by needle stick accident, close personal contact or perinatal transmission.

Comparison of a modified microagglutination technique for HBsAg with the standard technique and a new RIA system.

A further modification of the standard RPHA technique (Hepatest, Wellcome Reagents) for the detection of HBsAg is described. This modification does not require a centrifugation step which is required by the other modifications that have been described previously and consequently takes a little longer to perform. It does, however, retain the advantages of increased sensitivity and decreased costs which are also features of the other modifications. A series of 939 routine clinical specimens were used to evaluate the method described and to evaluate a new RIA kit for the detection of HBsAg (Hepatube, Wellcome Reagents). Of 53 specimens found to be positive for HBsAg by RIA, 50 (94% were detected by the modified Hepatest RPHA as opposed to 47 (89%) by the standard technique.

Histopathology and localization of viral antigens in the liver of HBsAg positive homosexuals.

In a survey of the prevalence of chronic hepatitis B in a male homosexual population, liver biopsies were done in 28 asymptomatic patients who had persistently raised aminotransferases. Four patients had active cirrhosis (AC), 13 had chronic active hepatitis (CAH) of various degrees of severity and 11 had either chronic persistent hepatitis (CPH) or minor changes of the type seen in hepatitis B virus carriers. Core associated antigens and surface antigen, were demonstrated by the PAP immunoperoxidase method in 20 cases. Core and surface antigens tended to be present in the same areas of the biopsy and quantitation showed higher core to surface antigen ratios in CAH than in CPH, the difference being statistically significant. In seven cases no core-associated antigens were demonstrated in the presence of surface antigen: most of these patients had either inactive disease or active cirrhosis. In one carrier neither antigen was demonstrated. Ten patients had two or more biopsies. Four of these had no treatment and the amounts of core and surface positive cells in the liver did not increase. Six were treated with immunosuppressants. This did not alter the degree of either inflammation or fibrosis. but the number of surface and core antigen positive cells in the liver was higher after treatment in almost every case.

IgM responses to hepatitis-A virus and hepatitis-B core antigen in acute and chronic liver disease in Malawi; possible role of non-A, non-B, hepatitis.

Of 33 patients with acute hepatitis in Malawi, 21 had infection by hepatitis-B virus (HBV), five by hepatitis-A virus (HAV) and seven, who had no markers of current HBV or HAV infections, were probably infected by the agent(s) of non-A, non-B, hepatitis. 87 of 88 sera from persons without liver disease contained antibody to HAV and 49 antibody to hepatitis-B surface antigen (anti-HBs) (six were positive for hepatitis-B surface antigen). The diagnosis of recent infection by HAV was made by detecting HAV-specific IGM in single serum samples and, although such tests showed that HAV caused acute hepatitis, its absence in patients with chronic liver disease suggests that, unlike HBV, infection by HAV does not play a role in chronic liver disease in Malawi. Anti-hepatis-B core antigen (anti-HBc)-specific IgM was detected in 19 of 21 patients with acute HBV infection, in three of five HbsAg-positive patients with cirrhosis, but in none of five HbsAg-positive patients with hepatoma.

IgM responses to hepatitis-A virus and hepatitis-B core antigen in acute and chronic liver disease in Malawi; possible role of non-A; non-B; hepatitis

Of 33 patients with acute hepatitis in Malawi; 21 had infection by hepatitis-B virus (HBV); five by hepatitis-A virus (HAV) and seven; who had no markers of current HBV or HAV infections; were probably infected by the agent(s) of non-A; non-B; hepatitis. 87 of 88 sera from persons without liver disease contained antibody to HAV and 49 antibody to hepatitis-B surface antigen (anti-HBs) (six were positive for hepatitis-B surface antigen). The diagnosis of recent infection by HAV was made by detecting HAV-specific IGM in single serum samples and; although such tests showed that HAV caused acute hepatitis; its absence in patients with chronic liver disease suggests that; unlike HBV; infection by HAV does not play a role in chronic liver disease in Malawi. Anti-hepatis-B core antigen (anti-HBc)-specific IgM was detected in 19 of 21 patients with acute HBV infection; in three of five HbsAg-positive patients with cirrhosis; but in none of five Hbs Ag-positive patients with hepatoma