Examples of proper reporting for evaluation (Stage 2 validation) of diagnostic tests for diseases listed by the World Organisation for Animal Health.

Reporting and design standards are key indicators of the quality of diagnostic accuracy (validation) studies but, with the exception of aquatic animal diseases and paratuberculosis in ruminants, there is limited guidance for designing these studies in animals. There is, therefore, a need for generic guidelines that are based on disease characteristics, such as mode of transmission, latent period and pathogenesis. Comprehensive, clear and transparent reporting of primary test accuracy studies for diseases listed by the World Organisation for Animal Health (OIE) has value for the end users of diagnostic tests and, ultimately, for decision-makers, who require systematic reviews and meta-analysis of multiple tests for specified diseases and testing purposes. The recent publication of reporting standards for Bayesian latent class models, to analyse test-accuracy data from naturally occurring disease events, fills an important gap as these methods are being increasingly used for OIE-listed diseases. Adherence to design and reporting standards, as well as to guidelines, helps to ensure that research funding for test validation studies is used appropriately and that the strengths and limitations of single tests or test combinations are made clear to test users. The authors provide a review of key points that are often overlooked or misinterpreted in test validation studies, as well as two concrete examples of good practice for use as a reference point for future studies.

Les normes de notification et de conception sont des indicateurs essentiels de la qualité des études de validation des tests destinées à déterminer leur exactitude diagnostique ; or, en dehors des maladies des animaux aquatiques et de la paratuberculose chez les ruminants, il n'existe guère de lignes directrices pour concevoir ce type d'études pour les tests utilisés en santé animale. À la connaissance des auteurs, il n'existe pas non plus de normes de conception applicables aux études de validation en santé humaine. Par conséquent, il conviendrait de disposer de lignes directrices génériques fondées sur les caractéristiques des maladies telles que leurs modalités de transmission, leur période de latence et leur pathogénie. Une notification complète, claire et transparente des études d'exactitude des tests primaires pour les maladies listées par l'Organisation mondiale de la santé animale (OIE) serait une aide précieuse pour les utilisateurs finaux des tests de diagnostic, mais aussi pour les responsables de l'élaboration des politiques, dont les décisions reposent sur des examens et des méta-analyses systématiques couvrant un grand nombre de tests pour certaines maladies ou pour certains usages d'un test. La publication récente des normes de notification applicables aux modèles bayésiens à classe latente pour analyser les données de performance d'un test à partir de foyers naturels de maladie comble une lacune importante dans la mesure où ces méthodes sont de plus en plus utilisées pour les maladies listées par l'OIE. L'adhésion à des normes de conception et de notification ainsi qu'à des lignes directrices en la matière permettra de garantir que les fonds alloués aux études de validation des tests sont bien utilisés et que les atouts et les limitations de certains tests individuels ou associations de tests sont clairement perçus par les utilisateurs. Les auteurs passent en revue certains points essentiels qui sont souvent ignorés ou mal interprétés lors des études de validation des tests et proposent deux exemples concrets de bonnes pratiques qui pourront servir de références pour les études à venir.

Las normas de comunicación y diseño son indicadores básicos de la calidad de los estudios encaminados a determinar la exactitud de diagnóstico (validación) pero, con la excepción de las enfermedades de los animales acuáticos y la paratuberculosis en rumiantes, hay escasas directrices que se apliquen al diseño de esos estudios en animales. Además, hasta donde saben los autores, en el ámbito de la salud humana no hay normas de diseño. De ahí la necesidad de directrices genéricas que estén basadas en las características de las enfermedades, como modo de transmisión, período de latencia o patogénesis. La comunicación exhaustiva, clara y transparente de estudios primarios sobre la exactitud de pruebas de diagnóstico de enfermedades incluidas en las listas de la Organización Mundial de Sanidad Animal (OIE) reviste utilidad no solo para los usuarios finales de la prueba, sino también, en última instancia, para los órganos decisorios, que necesitan metaanálisis y estudios sistemáticos de múltiples pruebas que se apliquen a una u otra enfermedad y sirvan para una u otra finalidad. La reciente publicación de normas de comunicación de modelos bayesianos de clases latentes para analizar los datos de exactitud de pruebas a partir de episodios de enfermedad de origen natural viene a colmar una importante laguna, en la medida en que estos métodos se aplican cada vez más al diagnóstico de enfermedades incluidas en las listas de la OIE. El cumplimiento de las normas de diseño y comunicación, y también de las directrices, ayuda a garantizar que los fondos de investigación destinados a estudios de validación de pruebas sean utilizados debidamente y que el usuario final de una prueba reciba información clara sobre los puntos fuertes y las limitaciones de una prueba o combinación de pruebas. Los autores pasan revista a los principales aspectos que se suelen pasar por alto o malinterpretar en los estudios de validación de pruebas y ofrecen dos ejemplos concretos de buenas prácticas que se pueden utilizar como referencia en futuros estudios.

Novel real-time PCR detection assay for Brucella suis.

INTRODUCTION: Brucella suis is the causative agent of brucellosis in suidae and is differentiated into five biovars (bv). Biovars 1 and 3 possess zoonotic potential and can infect humans, whereas biovar 2 represents the main source of brucellosis in feral and domestic pigs in Europe. Both aspects, the zoonotic threat and the economic loss, emphasize the necessity to monitor feral and domestic pig populations. Available serological or PCR based methods lack sensitivity and specificity. RESULTS: Here a bioinformatics approach was used to identify a B. suis specific 17 bp repeat on chromosome II (BS1330_II0657 locus). This repeat is common for B. suis bv 1 to 4 and was used to develop a TaqMan probe assay. The average PCR efficiency was determined as 95% and the limit of detection as 12,5 fg/µl of DNA, equally to 3.7 bacterial genomes. This assay has the highest sensitivity of all previously described B. suis specific PCR assays, making it possible to detect 3-4 bacterial genomes per 1 µl of sample. The assay was tested 100% specific for B. suis and negative for other Brucella spp. and closely related non-Brucella species. CONCLUSIONS: This novel qPCR assay could become a rapid, inexpensive and reliable screening method for large sample pools of B. suis 1 to 4. This method will be applicable for field samples after validation.

Effect of incubation temperature on the diagnostic sensitivity of the glanders complement fixation test.

The complement fixation test (CFT) is the only serological test prescribed by the World Organisation for Animal Health (OIE) for the diagnosis of glanders in international trading of equids. However, false-positive reactions have caused financial losses to the animal owners in the past, and false-negative tests have resulted in the introduction of glanders into healthy equine populations in previously glanders-free areas. Both warm (incubation at 37°C for 1 h) and cold (overnight incubation at 4°C) procedures are recommended by the OIE for serodiagnosis of glanders. In a comparison of the sensitivity and specificity of the two techniques, using the United States Department of Agriculture antigen, warm CFT was found to be significantly less sensitive (56.8%; p < 0.0005) than the cold CFT (83.6%). Cold CFT thus increases the detection rate of glanders but a lower diagnostic specificity has to be accepted. The immunoblot was used as the gold standard.

Glanders in animals: a review on epidemiology, clinical presentation, diagnosis and countermeasures.

Glanders or farcy, caused by Burkholderia mallei, is an infectious and zoonotic disease of solipeds. Horses, donkeys and mules are the only known natural reservoir of B. mallei. Although glanders has been eradicated from most countries, it has regained the status of a re-emerging disease because of the numerous recent outbreaks. Pre-symptomatic or carrier animals are the potential source of infection for the healthy equine population and play a crucial role in the spreading of the infectious agent. Glanders is characterized by ulcerating nodular lesions of the skin and mucous membrane. Generalized symptoms include fever, malaise, depression, cough, anorexia and weight loss. Burkholderia mallei can invade its host through mucous membranes, gastrointestinal tract and the integument. Its virulence mechanisms and pathogenesis are not yet completely understood. A major problem when using serological tests for diagnosing glanders is the occurrence of false-positive and false-negative results leading to difficulties in international trade with equids and to the spread of glanders to disease-free regions. Moreover, poor tests critically result in poor control of disease. These tests are not only incapable of discriminating between B. mallei and B. pseudomallei antibodies, they are also unable to differentiate between malleinized and naturally infected animals. Combined use of both serological and molecular detection methods increases the detection rate of glanders. Countermeasures against glanders include early detection of disease in susceptible animals, stringent quarantine measures, testing and safe destruction of infected carcasses, adequate compensation to the animal owners, disinfection of infected premises and awareness about glanders and the zoonotic implications through veterinary extension services. An account of the clinical picture and successful experimental therapy of spontaneous equine glanders is also given.

Comparative evaluation of three commercially available complement fixation test antigens for the diagnosis of glanders.

The sensitivity and specificity of three commercially available complement fixation test (CFT) antigens from c.c.pro (c.c.pro), Central Veterinary Institute of Wageningen UR (CIDC) and the United States Department of Agriculture (USDA) were comparatively evaluated by testing 410 sera collected from glanders-endemic and non-endemic areas (200 true-negative randomly collected sera and 210 sera collected from experimentally immunised animals (12 rabbits, 19 horses), clinically positive (135) and culture-positive (44) horses, donkeys and mules). Immunoblotting (IB) was used as the gold standard test. Highest sensitivity was shown for the CIDC antigen (100 per cent) followed by the c.c.pro antigen (99.39 per cent). However, the USDA antigen showed substantially less (p<0.05) sensitivity (62.19 per cent). Highest specificity was found for the USDA antigen (100 per cent) followed by the CIDC (97.5 per cent) and c.c.pro antigen (96.5 per cent). Positive and negative predictive values (assumed glanders prevalence of <0.1 per cent) for each antigen were calculated to be 95.88 and 99.48 (c.c.pro), 97.04 and 100 (CIDC), 100 and 76.33 per cent (USDA), respectively. Almost perfect agreement (0.96) was found between CFT using either c.c.pro or CIDC and IB.