Sensitivity, specificity and comparison of three commercially available immunological tests in the diagnosis of Cryptosporidium species in animals

ABSTRACT The study was conducted to compare the specificity of immunological diagnostic methods used for the diagnosis of Cryptosporidium species capable of causing life-threatening infection in both immunosuppressed and immunocompetent patients. For the detection of Cryptosporidium species in 79 animals with diarrhoea, we used three Copro-antigen tests: RIDASCREEN® Cryptosporidium test, Cryptosporidium 2nd Generation (ELISA) and RIDA®QUICK Cryptosporidium. For immunoassays we used positive and negative samples detected by means of polymerase chain reaction and validated by sequencing and nested polymerase chain reaction to confirm the presence six different species of Cryptosporidium species. Prevalence of cryptosporidiosis in the entire group determined by enzyme immunoassay, enzyme linked immunosorbent assay, immuno-chromatographic test and polymerase chain reaction was 34.17%, 27.84%, 6.33% and 27.84%, respectively. Sensitivity of animal samples with enzyme immunoassay, enzyme linked immunosorbent assay, and immuno-chromatographic test was 63.6%, 40.9% and 22.7%, resp., when questionable samples were considered positive, whereas specificity of enzyme immunoassay, enzyme linked immunosorbent assay and immuno-chromatographic test was 75.9%, 78.9% and 100%, respectively. Positive predictive values and negative predictive values were different for all the tests. These differences results are controversial and therefore reliability and reproducibility of immunoassays as the only diagnostic method is questionable. The use of various Cryptosporidium species in diagnosis based on immunological testing and different results obtained by individual tests indicate potential differences in Copro-antigens produced by individual Cryptosporidium species.

Costo-beneficio de las investigaciones inmunológicas en el Instituto Superior de Medicina Militar “Dr Luis Díaz Soto” / Cost-benefit of immunological research tests performed at “Dr Luis Díaz Soto” Higher Institute of Military Medicine

Se realizó un estudio retrospectivo (1996 a 1999) del costo-beneficio de las pruebas inmunológicas realizadas en el Instituto Superior de Medicina Militar “Dr Luis Díaz Soto”. Se crearon bases de datos con todas las pruebas realizadas en el Laboratorio de Inmunología de dicho instituto y se trabajó con los totales y variación de porcentajes de pruebas alteradas. El estudio demostró que antes de la intervención de los especialistas en el diagnóstico inmunológico se indicaban demasiadas pruebas por diversas causas. Se proponen estrategias educativas al personal médico y paramédico para disminuir el gasto de materiales y reactivos, y con ello aumentar la calidad del trabajo

A comparison of three malaria diagnostic tests, under field conditions in North-west Thailand.

A hospital-based trial to compare the clinical diagnosis of malaria; microscopy, and a rapid diagnostic antigen capture detection dipstick (ParaSight-F) was conducted in North-west Thailand. 301 people who presented themselves at the hospital were selected. 204 (68%) were presumptively diagnosed as having malaria by the triage nurses; 64 (21.3%) were P. falciparum parasite positive, and 94 (32%) tested positive for P. falciparum with the ParaSight-F test strips. There was no association between hemoglobin levels (<10g/dl and > or = 10g/dl) and malaria, and although there was a good statistical association between temperature and malaria the specificity, sensitivity and positive predictive values were all low, indicating that temperature alone is a poor indicator of the disease. Based on the microscopy results, we found that a presumptive clinical diagnosis dramatically over-diagnosed malaria, and similarly there were a large number of false positives using the ParaSight-F test. We believe that many of the patients had received some form of malaria treatment prior to presentation at the hospital, and that the high number of false positives are explained by persistent antigenemia and the possibility of there being sequestered parasites following incomplete chemotherapy.

Immunodiagnosis of snake venom poisoning.

Uncertainty as to the species diagnosis remains a serious problem in the management of snake venom poisoning. This is particularly so in areas inhabited by numerous species, the venoms of which elicit similar pharmacological effects and clinical symptoms and against which para-specific cross-neutralizing antivenom is not available. Attempts have been made to eliminate some of this ambiguity through the development of various immunodiagnostic tests. Tests based on ELISA are sensitive, specific and even quantitative and adaptable to field application. In the development of diagnostic tests for use in developing countries, however, practical consideration must be given to speed, cost, simplicity in terms of equipment and expertise, and stability to the climate and storage conditions. This may dictate further modification or selection of more suitable alternative methodologies. Furthermore, the test may have to allow more flexibility in accommodating local species distributions and to address probable complications of heterophile antibodies in test samples from rural people.