Detection of Mycobacterium avium subsp. paratuberculosis in bovine fecal samples: comparison of three polymerase chain reaction-based diagnostic tests with a conventional culture method.

Three commercially available assays, designed to specifically detect the presence of Mycobacterium avium subsp. paratuberculosis (MAP) in fecal samples by IS900-PCR, were compared with a conventional culture method. Fecal samples from 100 dairy cows were tested. Fifty-four (67.5%) of 80 culture-positive samples were positive for an assay that detects MAP DNA by dot spot hybridization of polymerase chain reaction products (kit A), 48 (60%) were positive by an assay using ethidium bromide staining for agar gel visualization of amplification products (kit B), and 49 (61.3%) were positive by an assay in which amplified products are detected by a colorimetric detection system (kit C). Relative sensitivity of all tests increased in proportion to the presence of MAP in fecal samples. Specificity was 100% based on results from 20 culture-negative samples from an MAP-free herd.     

Haemophilus somnus: a comparison among three serological tests and a serological survey in beef and dairy cattle.

Serological tests for the detection of antibodies against Haemophilus somnus were carried out in herds of beef and dairy cattle using three different techniques: agglutination, complement fixation and counterimmunoelectrophoresis. The agglutination test appeared to detect more seroreactors than the complement fixation and counterimmunoelectrophoresis tests. Results of the three tests indicated that there were more positive reactors in beef cattle and dairy cattle from infected herds than in dairy cattle from clinically normal herds.     

Paratuberculosis in cattle: a comparison of three serologic tests with results of fecal culture

Feces and blood were collected from cattle in 13 herds known to be infected with Mycobacterium paratuberculosis to evaluate a complement-fixation (CF) test, an agar gel immunodiffusion (AGID) test and an enzyme-linked immunosorbent assay (ELISA) for the serologic diagnosis of paratuberculosis. M. paratuberculosis was isolated from the feces of 36 of 192 cattle examined. Twenty-three culture-positive animals had CF test titers regarded as suspect or positive, 10 were positive by the AGID test and 34 were suspect or positive by the ELISA. Of the 156 culture-negative animals, the CF test agreed on 136, the ELISA on 129 and the AGID on 151.     

A comparison of three serological tests in the diagnosis of caprine brucellosis.

The serum agglutination test (SAT), the Rose Bengal plate test (RBPT) and the milk ring test (MRT) were used in the diagnosis of caprine brucellosis. There was a close correlation between the SAT and RBPT when both tests were negative but the RBPT failed to detect 79.82 per cent of sera in excess of 50 iu. Also, owing to the relatively poor milking potential of the Nigerian goat and the false positive results with the MRT, it is concluded that the SAT offers a better serological diagnostic tool for caprine brucellosis in this locality.     

A comparison of diagnostic tests for hairy shaker disease

Abstract

Extract

From 1982 to 1988, the virus culture interference assay was used by the Animal Health Laboratory Network as a diagnostic test for hairy shaker (HS) disease (known as border disease in the United Kingdom). However, this assay is slow and relatively expensive, and in some studies of the prevalence of HS disease it gave inexplicably high rates of 28–33% ⁽¹⁾ Orr, MB and Montgomery, RH. 1983. Hairy shaker update in Otago and Southland. Surveillance, 10(4): 13–13.  [Google Scholar] ⁽²⁾ Smith, KR. 1986. Hairy shaker disease: Estimate of the true prevalence of this disease in Otago and Southland. Surveillance, 13(2): 8–9.  [Google Scholar] ⁽³⁾ Orr, MB. 1988. Sheep abortions - Invermay 1988. Surveillance, 16(3): 24–25.  [Google Scholar]) compared with other studies in which the prevalence rates were 1–8% ⁽⁴⁾ Horner, G. 1983. Hairy shaker disease: The North Island situation. Surveillance, 10(3): 21–22.  [Google Scholar] (G. Horner, pers. comm.) The present project was designed to compare the virus culture interference test with an immunoperoxidase (IPX) method and an antigen capture ELISA for the detection of HS virus.     

Implantation of VX2 carcinoma into the liver of rabbits: a comparison of three direct-injection methods

The efficacy of agarose in preventing VX2 carcinoma cell leakage was evaluated and the results were compared with two traditional methods. Forty-five rabbits were divided into 3 groups: Group 1, VX2 tumor cells were injected directly into the liver and no special procedure after removal of the needle; Group 2, the puncture site was gently compressed, using an alcoholic cotton gauze, for three minutes; Group 3, 0.2 ml of heated liquid agarose was injected to seal the aperture after injection of VX2 cells. The leakage rates were 80%, 53.3% and 6.6% for group 1, group 2 and group 3, respectively. We consider agarose is a useful material in preventing the leakage in the establishment of VX2 liver tumor models.     

Using and interpreting diagnostic tests.

Diagnostic tests are invaluable to the practice of veterinary medicine. Using them correctly and interpreting the results appropriately depend on having a good understanding of the basic principles outlined in this article. Topics covered include sensitivity and specificity, agreement among tests, using multiple tests, and other issues related to the use and interpretation of diagnostic tests. The most important principle is recognition that the interpretation of test results varies across populations and requires an estimate of the prevalence of the infection (or disease) in the population being studied.     

A comparison of three serological tests for the diagnosis of B. ovis infection in rams

The complement fixation test (CFT), the enzyme labelled immunosorbent assay (ELISA) and the gel diffusion precipitin test (GD) were compared, for the diagnosis of Brucella ovis infection in rams. The sensitivities of the tests in 109 rams which were shedding B. ovis in their semen were: CFT 96.3%; ELISA 97.2%; GD 91.7%. The specificities of the tests in 141 rams from non-infected flocks were: CFI 99.3%; ELISA 98.6%; GD 100%. Predictive values of the three tests were measured in 285 rams from infected flocks. Thirty-eight percent of these rams were shedding B. ovis in their semen. Predictive values of positive tests were: CFT 75.5%; ELISA 66.7%; GD 72.5%. Predictive values of negative tests were: CFI 97.1%; ELISA 97.6%; GD 93.8%.     

Comparative diagnostic potential of three serological tests for abortive Q fever in goat herds

Performances of an ELISA, an immunofluorescence assay (IFA) and a complement fixation test (CFT) were assessed for detecting antibodies against Coxiella burnetii after Q fever abortions in naturally infected goats. The goal of the study was to provide information useful for veterinary serodiagnosis in regard to categories of goats either experiencing Q fever abortion or not, blood sampling times and recommended cut-offs. The study was conducted on eight goat herds with evidence of C. burnetii abortions. In each herd, at least 5 goats that had aborted and 10 goats prior to parturition or at term were monitored 15, 30 and 60 days (D15, D30, D60) after the onset of Q fever abortion. The overall CFT results distribution did not differ between the two groups of goats and showed poor agreement with the ELISA results. In contrast, the ELISA and IFA results revealed comparable significant differences, but overall the ELISA test was slightly more sensitive than the IFA test. Seroprevalence, according to ELISA and IFA respectively, was higher in the aborting (88% and 82%) than in the non-aborting group (60% and 50%). High levels of serum antibodies were detected in goats post-abortion with an average of 114 %OD using ELISA and a log10(titer) of 2.4 using IFA. Strongly positive ELISA (%OD>80) and positive IFA results (log10(titers)>1.9) were significantly associated with abortion. Sampling on D15 gave the best association with ORs of 10 for ELISA and 6 for IFA. The practical interest of these results is discussed.     

Bovine herpesvirus 4 isolates: a comparison of three major glycoproteins.

Twenty-four Belgian field isolates of bovine herpesvirus 4 (BHV-4), together with four reference strains were compared by radio-immunoprecipitation and western blotting using a polyvalent antiserum and monoclonal antibodies raised against major glycoproteins. Most of these strains showed the same protein profile as the European reference strain Movar 33/63. For two strains the molecular weight of gp 6, p (gp 10/gp 17) and gp 10 were the same as those of the American reference strain DN 599. No relationship could be established between the protein profiles and origin of the isolates or with the restriction patterns. This study provides a view of the molecular weight variations of the major BHV-4 glycoproteins among field isolates.     

Evaluating aggressive behavior in dogs: a comparison of 3 tests

This study assessed the consistency with which aggressive behavior occurred across 3 different provocation tests that are currently used in practice to evaluate the behavior and safety of dogs. The aim of this study was not to validate the tests, but to evaluate tests that are not validated but are nevertheless being used in a legal context in Switzerland, by investigating the hypothesis that 3 different approaches, all claiming to correctly evaluate the behavior of dogs, should be expected to show significant agreement. The same 60 dogs were tested in 3 behavioral tests being used in Switzerland at the time of this study in the year 2003 (Test A: Test of the American Staffordshire Terrier Club; Test B: Halterprüfung; Test C: Test of the Canton of Basel-Stadt). “Intraspecific behavior” and “interspecific behavior toward humans” that might relate to potential aggressive behavior were of particular interest.The observed agreement among the 3 tests was compared relative to chance using a κ test. Significant but low levels of agreement were found among the 3 tests for the criterion “intraspecific behavior” (κ = 0.133, P = .014), with the highest correlation between Tests A and B (κ = 0.345, P < .001) and for the criterion “interspecific behavior” (κ = 0.135, P = 0. 014), with Tests A and B (κ = 0.220, P = .005) showing the highest correlation. However, significant absolute values of κ were low in all cases. In a further analysis, dogs evaluated to show no signs of potential aggression in the test situations by all 3 tests were eliminated, and the results of the remaining dogs (“interspecific behavior,” n = 23; “intraspecific behavior,” n = 29) were assessed for disagreement in pairwise combinations using a McNemar chi-square test. No significant levels of disagreement were found for “intraspecific behavior,” however, for “interspecific behavior,” Tests A and B (P = .035), and Tests B and C (P < .001) differed significantly, with no significant difference between Tests A and B (P = 0.11). The inconsistency of the results from different tests suggests test bias at the very least and questions the validity of these tests. Further work examining the validity of each individual test is warranted if they are to be used in a legal context.     

Diagnosis of enzootic bovine leukosis: a comparison of haematological and immunodiffusion tests.

A total of 657 cattle from three different herds were tested for the presence of specific antibodies against EBL antigens by means of the immunodiffusion test and the results compared with the classification according to the lymphocyte counts. All animals with pathologically raised lymphocyte counts showed a positive immunodiffusion test reaction. In the majority of these both antigens, 'p24' and 'gp', gave positive results; in a smaller number antibodies against the gp antigen only were detected, but never against the p24 antigen only. It is concluded that for field testing programmes the use of the gp antigen is sufficient. In future experiments, however, both antigens should be employed, because the lack of one of them might perhaps prove to be correlated with the future course of the disease. The absence of specific antibodies, together with a normal number of lymphocytes, in young animals should, however, not lead to the conclusion that they are free of the disease.     

Critically appraising studies reporting assessing diagnostic tests.

Studies that report the sensitivity and specificity of diagnostic tests are susceptible to flaws that can introduce bias and lead to incorrect estimates. This article uses the quality assessment of diagnostic accuracy studies checklist to describe how to appraise a study reporting diagnostic test comparisons critically. The article also contains a glossary of terms that are useful in discussions about diagnostic tests.     

A comparison of three rapid diagnostic methods for the detection of rotavirus infection in calves

Three techniques for the detection of rotavirus in faecal samples from calves with neonatal gastroenteritis were compared. A preliminary study indicated that reverse passive haemagglutination (RPHA) was at least as sensitive as the enzyme-linked immunosorbent assay (ELISA). These two immunoassays were compared with the detection of viral RNA by polyacrylamide gel electrophoresis (PAGE) on 209 field samples. Of the 77 samples in which at least one test gave a positive result, 69 were positive by both RPHA and PAGE, but only 49 were also positive by ELISA, indicating a lower sensitivity for the latter test. The overall agreement between RPHA and PAGE was 96%. The reasons for the discrepancies between the tests are discussed.     

Ordering diagnostic tests in cardiovascular disease

All heart patients should have an electrocardiogram, radiographs of the chest, and blood work done in addition to a complete history and physical examination. In ordering diagnostic tests, the real point is to understand the rationale for each test ordered, what information may be expected from the test, and if there is a justifiable reason for each test considering the factors involved.