Field performance of two rapid screening tests in active surveillance of transmissible spongiform encephalopathies in small ruminants

Recently, screening tests for monitoring the prevalence of transmissible spongiform encephalopathies specifically in sheep and goats became available. Although most countries require comprehensive test validation prior to approval, little is known about their performance under normal operating conditions. Switzerland was one of the first countries to implement 2 of these tests, an enzyme-linked immunosorbent assay (ELISA) and a Western blot, in a 1-year active surveillance program. Slaughtered animals (n = 32,777) were analyzed in either of the 2 tests with immunohistochemistry for confirmation of initial reactive results, and fallen stock samples (n = 3,193) were subjected to both screening tests and immunohistochemistry in parallel. Initial reactive and false-positive rates were recorded over time. Both tests revealed an excellent diagnostic specificity (>99.5%). However, initial reactive rates were elevated at the beginning of the program but dropped to levels below 1% with routine and enhanced staff training. Only those in the ELISA increased again in the second half of the program and correlated with the degree of tissue autolysis in the fallen stock samples. It is noteworthy that the Western blot missed 1 of the 3 atypical scrapie cases in the fallen stock, indicating potential differences in the diagnostic sensitivities between the 2 screening tests. However, an estimation of the diagnostic sensitivity for both tests on field samples remained difficult due to the low disease prevalence. Taken together, these results highlight the importance of staff training, sample quality, and interlaboratory comparison trials when such screening tests are implemented in the field.

Screening and prediction of erosive potential

The literature on the erosive potential of drinks and other products is summarised, and aspects of the conduct of screening tests as well as possible correlations of the erosive potential with various solution parameters are discussed. The solution parameters that have been suggested as important include pH, acid concentration (with respect to buffer capacity and concentration of undissociated acid), degree of saturation, calcium and phosphate concentrations, and inhibitors of erosion. Based on the available data, it is concluded that the dominant factor in erosion is pH. The effect of buffer capacity seems to be pH dependent. The degree of saturation probably has a non-linear relationship with erosion. While calcium at elevated concentrations is known to reduce erosion effectively, it is not known whether it is important at naturally occurring concentrations. Fluoride at naturally occurring concentrations is inversely correlated with erosive potential, but phosphate is probably not. Natural plant gums, notably pectin, do not inhibit erosion, so they are unlikely to interfere with the prediction of erosive potential. The non-linearity of some solution factors and interactions with pH need to be taken into account when developing multivariate models for predicting the erosive potential of different solutions. Finally, the erosive potential of solutions towards enamel and dentine might differ.

Unexplained syncope--is screening for carotid sinus hypersensitivity indicated in all patients aged >40 years?

OBJECTIVE: To determine the frequency, age distribution and clinical presentation of carotid sinus hypersensitivity (CSH) among 373 patients (age range 15-92 years) referred to two autonomic referral centres during a 10-year period. METHODS: Carotid sinus massage (CSM) was performed both supine and during 60 degree head-up tilt. Beat-to-beat blood pressure, heart rate and a three-lead electrocardiography were recorded continuously. CSH was classified as cardioinhibitory (asystole > or = 3 s), vasodepressor (systolic blood pressure fall > or = 50 mm Hg) or mixed. All patients additionally underwent autonomic screening tests for orthostatic hypotension and autonomic failure. RESULTS: CSH was observed in 13.7% of all patients. The diagnostic yield of CSM was nil in patients aged < 50 years (n = 65), 2.4% in those aged 50-59 years (n = 82), 9.1% in those aged 60-69 years (n = 77), 20.7% in those aged 70-79 years (n = 92) and reached 40.4% in those > 80 years (n = 57). Syncope was the leading clinical symptom in 62.8%. In 27.4% of patients falls without definite loss of consciousness was the main clinical symptom. Mild and mainly systolic orthostatic hypotension was recorded in 17.6%; evidence of sympathetic or parasympathetic dysfunction was found in none. CONCLUSIONS: CSH was confirmed in patients > 50 years, the incidence steeply increasing with age. The current European Society of Cardiology guidelines that recommend testing for CSH in all patients > 40 years with syncope of unknown aetiology may need reconsideration. Orthostatic hypotension was noted in some patients with CSH, but evidence of sympathetic or parasympathetic failure was not found in any of them.

Predicting the population impact of chlamydia screening programmes: comparative mathematical modelling study

BACKGROUND: Published individual-based, dynamic sexual network modelling studies reach different conclusions about the population impact of screening for Chlamydia trachomatis. The objective of this study was to conduct a direct comparison of the effect of organised chlamydia screening in different models. METHODS: Three models simulating population-level sexual behaviour, chlamydia transmission, screening and partner notification were used. Parameters describing a hypothetical annual opportunistic screening program in 16-24 year olds were standardised, whereas other parameters from the three original studies were retained. Model predictions of the change in chlamydia prevalence were compared under a range of scenarios. RESULTS: Initial overall chlamydia prevalence rates were similar in women but not men and there were age and sex-specific differences between models. The number of screening tests carried out was comparable in all models but there were large differences in the predicted impact of screening. After 10 years of screening, the predicted reduction in chlamydia prevalence in women aged 16-44 years ranged from 4% to 85%. Screening men and women had a greater impact than screening women alone in all models. There were marked differences between models in assumptions about treatment seeking and sexual behaviour before the start of the screening intervention. CONCLUSIONS: Future models of chlamydia transmission should be fitted to both incidence and prevalence data. This meta-modelling study provides essential information for explaining differences between published studies and increasing the utility of individual-based chlamydia transmission models for policy making.

Monitoring thrombin generation by electrochemistry: development of an amperometric biosensor screening test for plasma and whole blood

BACKGROUND: Complete investigation of thrombophilic or hemorrhagic clinical presentations is a time-, apparatus-, and cost-intensive process. Sensitive screening tests for characterizing the overall function of the hemostatic system, or defined parts of it, would be very useful. For this purpose, we are developing an electrochemical biosensor system that allows measurement of thrombin generation in whole blood as well as in plasma. METHODS: The measuring system consists of a single-use electrochemical sensor in the shape of a strip and a measuring unit connected to a personal computer, recording the electrical signal. Blood is added to a specific reagent mixture immobilized in dry form on the strip, including a coagulation activator (e.g., tissue factor or silica) and an electrogenic substrate specific to thrombin. RESULTS: Increasing thrombin concentrations gave standard curves with progressively increasing maximal current and decreasing time to reach the peak. Because the measurement was unaffected by color or turbidity, any type of blood sample could be analyzed: platelet-poor plasma, platelet-rich plasma, and whole blood. The test strips with the predried reagents were stable when stored for several months before testing. Analysis of the combined results obtained with different activators allowed discrimination between defects of the extrinsic, intrinsic, and common coagulation pathways. Activated protein C (APC) predried on the strips allowed identification of APC-resistance in plasma and whole blood samples. CONCLUSIONS: The biosensor system provides a new method for assessing thrombin generation in plasma or whole blood samples as small as 10 microL. The assay is easy to use, thus allowing it to be performed in a point-of-care setting.

Cancer screening - principles, evaluation and implementation

Screening for malignant disease aims to reduce the population risk of impaired health due to the tumor in question. Screening does not only entail testing but covers all steps required to achieve the intended reduction in risk, from the appropriate information of the population to a suitable therapy. Screening tests are performed in individuals free or unaware of any symptoms associated with the tumor. An essential condition is a recognizable pathological abnormality, which occurs without symptoms and represents a pre-clinical, early stage of the tumor. Overdiagnosis and overtreatment have only recently been recognized as important problems of screening for malignant disease. Overdiagnosis is defined as a screening-detected tumor that would never have led to symptoms. In prostate-specific antigen (PSA) screening for prostate cancer 50 % - 70 % of screening-detected cancers represent such overdiagnoses. Similarly, in the case of mammography screening 20 % - 30 % of screening-detected breast cancers are overdiagnoses. The evaluation of screening interventions is often affected by biases such as healthy screenee effects or length and lead time bias. Randomized controlled trials are therefore needed to examine the efficacy and effectiveness of screening interventions and to define the rate of adverse outcomes such as unnecessary diagnostic evaluations, overdiagnosis and overtreatment. Unfortunately there is no independent Swiss body comparable to the National Screening Committee in the United Kingdom or the United States Preventive Services Task Force, which examines screening tests and programs and develops recommendations. Clearly defined goals, a central organization responsible for inviting eligible individuals, documentation and quality assurance and balanced information of the public are important attributes of successful screening programs. In Switzerland the establishment of such programs is hampered by the highly fragmented, Federal health system which allows patients to access specialists directly.

[Cervical cancer screening in Switzerland - current practice and future challenges]

At the beginning of the 20th Century, cervical cancer was the leading cause of death from cancer in women. A marked decline in cervical cancer has been observed since the 1960s, in parallel with the introduction of the Papanicolau (Pap) test as a cytological screening method. Today, Pap smear screening is still the most widely used tool for cervical cancer prevention. Testing for human papillomavirus (HPV) in cervical specimens or a combination of Pap and HPV testing are also now available. In this article we compare current guidelines for cervical cancer screening in Switzerland with those in other European countries. In view of the opportunities offered by HPV testing and, since 2008, HPV vaccination, current guidelines for cervical cancer screening should be updated. Both the choice of screening tests and general organization of cervical cancer screening should be reviewed.

Demenzverdacht, aber normale neuropsychologische Screening-Untersuchung - wie weiter?

Die Demenz betrifft viele, belastet Angehörige und führt zu hohen Kosten, weshalb die Schweiz eine Sensibilisierungskampagne lancierte, um u.a. die Früherkennung der Demenz zu fördern. Dank der Früherkennung erleben Patienten und Angehörige Vorteile, wie weniger Notfallzuweisungen oder spätere Heimeintritte. Die Früherkennung ist aber schwierig, wenn Patienten zwar Gedächtnisprobleme beklagen, die Screening-Tests aber normal ausfallen. Möglicherweise helfen Geruchstests und weitere klinische Zeichen bei der Entscheidung, welche Patienten weiter abgeklärt werden. Die Zeit für funktionelle Bildgebungen und Biomarker ist noch nicht reif. Zentral bleibt bei kognitiven Beschwerden und normalem Screening das Gespräch mit Patient und Angehörigen, um nächste Schritte gemeinsam zu beschliessen. Der Hausarzt nimmt dabei eine zentrale, koordinierende und beratende Funktion ein, um Menschen mit Gedächtnisstörungen kompetent und effizient zu betreuen.

Cognition and driving in older persons

In Switzerland, approximately 350,000 people aged 70 years or older own a valid driving license. By law, these drivers are medically assessed every other year, most commonly by their general practitioner, to exclude that a medical condition is interfering with their driving skills. A prerequisite for driving is the integration of high-level cognitive functions with perception and motor function. Ageing, per se, does not necessarily impair driving or increase the crash risk. However, medical conditions, such as cognitive impairment and dementia, become more prevalent with advancing age and may contribute to poor driving and an increased crash risk. The extent to which driving skills are impaired depends on the cause of dementia, disease severity, other co-morbidities and individual compensation strategies. Dementia often remains undiagnosed and therefore general practitioners (GPs) can find themselves in the difficult situation to disclose a suspicion about cognitive impairment and queries about medical fitness to drive, at the same time. In addition, the literature suggests that cognitive screening tests, most commonly used by GPs, have a limited role in judging whether an older person remains fit to drive. Further specialist assessment, for example in a memory clinic or on the road testing (ORT), may be helpful when the diagnosis or its implication for driving remain unclear. Here, we review the literature about cognition and driving, for GPs who advise older drivers who wish to continue driving.

Serodiagnosis of Echinococcus spp. infection: explorative selection of diagnostic antigens by peptide microarray

BACKGROUND: Production of native antigens for serodiagnosis of helminthic infections is laborious and hampered by batch-to-batch variation. For serodiagnosis of echinococcosis, especially cystic disease, most screening tests rely on crude or purified Echinococcus granulosus hydatid cyst fluid. To resolve limitations associated with native antigens in serological tests, the use of standardized and highly pure antigens produced by chemical synthesis offers considerable advantages, provided appropriate diagnostic sensitivity and specificity is achieved. METHODOLOGY/PRINCIPAL FINDINGS: Making use of the growing collection of genomic and proteomic data, we applied a set of bioinformatic selection criteria to a collection of protein sequences including conceptually translated nucleotide sequence data of two related tapeworms, Echinococcus multilocularis and Echinococcus granulosus. Our approach targeted alpha-helical coiled-coils and intrinsically unstructured regions of parasite proteins potentially exposed to the host immune system. From 6 proteins of E. multilocularis and 5 proteins of E. granulosus, 45 peptides between 24 and 30 amino acids in length were designed. These peptides were chemically synthesized, spotted on microarrays and screened for reactivity with sera from infected humans. Peptides reacting above the cut-off were validated in enzyme-linked immunosorbent assays (ELISA). Peptides identified failed to differentiate between E. multilocularis and E. granulosus infection. The peptide performing best reached 57% sensitivity and 94% specificity. This candidate derived from Echinococcus multilocularis antigen B8/1 and showed strong reactivity to sera from patients infected either with E. multilocularis or E. granulosus. CONCLUSIONS/SIGNIFICANCE: This study provides proof of principle for the discovery of diagnostically relevant peptides by bioinformatic selection complemented with screening on a high-throughput microarray platform. Our data showed that a single peptide cannot provide sufficient diagnostic sensitivity whereas pooling several peptide antigens improved sensitivity; thus combinations of several peptides may lead the way to new diagnostic tests that replace, or at least complement conventional immunodiagnosis of echinococcosis. Our strategy could prove useful for diagnostic developments in other pathogens.

Serological survey of bluetongue virus serotype-8 infection in South American camelids in Switzerland (2007-2008)

BACKGROUND: Outbreak of bluetongue virus serotype-8 (BTV-8) infection in domestic ruminants in Northern Europe. OBJECTIVE: To investigate the South American camelids' (SAC) susceptibility to BTV-8 infection, their role in the epidemiology of the disease, and the use of currently available serological screening tests in SAC in an endemic region. ANIMALS: Three hundred and fifty-four unvaccinated and 27 vaccinated SAC (170 llamas, 201 alpacas), ranging in age from 1 month to 17 years between June and August 2008. The SAC originated from 44 herds throughout the country, representing 10% of the Swiss SAC population. METHODS: Prospective, observational study of a convenience sample of SAC. Serum samples were analyzed with 2 serological screening tests. When results diverged, a 3rd ELISA was carried out for confirmation (ID Screen Bluetongue Competition ELISA kit). RESULTS: All sera from the 354 unvaccinated animals were negative in the endemic region. Reliable seroconversion was observed after administration of 2 doses of vaccine. CONCLUSIONS AND CLINICAL IMPORTANCE: This study suggests a low susceptibility of SAC to BTV-8 despite the presence of the virus in the cattle and small ruminant population, indicating that SAC do not play a major role in the epidemiology of BTV-8. Furthermore, these results indicate that commercially available serological tests for BTV-8 can be used in SAC.

The assessment of cognition in visually impaired older adults

Background: visual and cognitive impairments are common in later life. Yet there are very few cognitive screening tests for the visually impaired. Objective: to screen for cognitive impairment in the visually impaired. Methods: case-control study including 150 elderly participants with visual impairment (n = 74) and a control group without visual impairment (n = 76) using vision-independent cognitive tests and cognitive screening tests (MMSE and clock drawing tests (CDT)) which are in part vision dependent. Results: the scoring of the two groups did not differ in the vision-independent cognitive tests. Visually impaired patients performed poorer than controls in the vision-dependent items of the MMSE (T = 7.3; df: 148; P < 0.001) and in CDT (T = 3.1; df: 145; P = 0.003). No group difference was found when vision-independent items were added to MMSE and CDT. The test score gain by the use of vision-independent items correlated with the severity of visual impairment (P < 0.002). Conclusion: visually impaired patients benefit from cognitive tests, which do not rely on vision. The more visually impaired the greater the benefit.

Predicting and diagnosing abacavir and nevirapine drug hypersensitivity: from bedside to bench and back again

There is a growing discussion surrounding the issue of personalized approaches to drug prescription based on an individual's genetic makeup. This field of investigation has focused primarily on identifying genetic factors that influence drug metabolism and cellular disposition, thereby contributing to dose-dependent toxicities and/or variable drug efficacy. However, pharmacogenetic approaches have also proved valuable in predicting drug hypersensitivity reactions in selected patient populations, including HIV-infected patients receiving long-term antiretroviral therapy. In this instance, susceptibility has been strongly linked to genetic loci involved in antigen recognition and presentation to the immune system--most notably within the major histocompatibility complex (MHC) region--consistent with the notion that hypersensitivity reactions represent drug-specific immune responses that are largely dose independent. Here the authors describe their experiences with the development of pharmacogenetic approaches to hypersensitivity reactions associated with abacavir and nevirapine, two commonly prescribed antiretroviral drugs. It is demonstrated that prospective screening tests to identify and exclude individuals with a certain genetic makeup may be largely successful in decreasing or eliminating incidence of these adverse drug reactions in certain populations. This review also explores the broader implications of these findings.

Testing strategies and follow-up for coeliac disease in a general internal medicine outpatient department from 2000 to 2005

PRINCIPLES: Coeliac disease (gluten sensitive enteropathy) is a genetically determined disorder with an incidence in the general population that is comparable to type 2 diabetes mellitus. Awareness of this fact and of the often atypical and oligosymptomatic manifestations is only now gaining ground in the medical profession. A high index of suspicion is important in order to minimise diagnostic and therapeutic delay. METHODS: Testing patterns and follow-up for coeliac disease in our institution have been analysed retrospectively for the past five years. The current literature was reviewed with respect to recommendations for clinical practice. RESULTS: A total of 271 patients were tested for coeliac disease over a period of five years. Only in 24 patients were positive results found; after further work-up, the final number of cases with certain or presumed coeliac disease was four. Followup was often difficult, many patients being lost after a single visit. CONCLUSIONS: This study showed that the number of tests ordered in our institution, more often for abdominal than atypical symptoms, has started to increase in the past two years. It also showed that screening tests have found their place in general clinical practice, while the final choice of tests needs to be determined in accordance with available guidelines and local resources. Upper endoscopy with small bowel biopsy remains the gold standard for diagnosis, but its place in follow-up is less certain. Coeliac disease is a disorder for which there is a definite treatment (gluten free diet); if it is left untreated diminished quality of life and potentially serious complications may ensue. Further education of the medical profession regarding coeliac disease, its incidence, presentation and treatment, is clearly indicated..

Atypical scrapie in a Swiss goat and implications for transmissible spongiform encephalopathy surveillance

Different types of transmissible spongiform encephalopathies (TSEs) affect sheep and goats. In addition to the classical form of scrapie, both species are susceptible to experimental infections with the bovine spongiform encephalopathy (BSE) agent, and in recent years atypical scrapie cases have been reported in sheep from different European countries. Atypical scrapie in sheep is characterized by distinct histopathologic lesions and molecular characteristics of the abnormal scrapie prion protein (PrP(sc)). Characteristics of atypical scrapie have not yet been described in detail in goats. A goat presenting features of atypical scrapie was identified in Switzerland. Although there was no difference between the molecular characteristics of PrP(sc) in this animal and those of atypical scrapie in sheep, differences in the distribution of histopathologic lesions and PrP(sc) deposition were observed. In particular the cerebellar cortex, a major site of PrP(sc) deposition in atypical scrapie in sheep, was found to be virtually unaffected in this goat. In contrast, severe lesions and PrP(sc) deposition were detected in more rostral brain structures, such as thalamus and midbrain. Two TSE screening tests and PrP(sc) immunohistochemistry were either negative or barely positive when applied to cerebellum and obex tissues, the target samples for TSE surveillance in sheep and goats. These findings suggest that such cases may have been missed in the past and could be overlooked in the future if sampling and testing procedures are not adapted. The epidemiological and veterinary public health implications of these atypical cases, however, are not yet known.