Target product profile for readers of rapid diagnostic tests.

While equipment-free visual interpretation is a benefit of lateral-flow assays, automating the reading of rapid diagnostic tests promotes proper test performance, interpretation and reporting of the results. We have created a target product profile that describes the minimal and optimal characteristics of various rapid diagnostic test readers. The product profile is intended to promote the development of effective, useful, sustainable rapid diagnostic test readers in support of health programmes worldwide. These readers may be custom hardware or software-only running on a general-purpose mobile device, for professional or lay use, and for medical or non-medical purposes. During the development of the product profile, the World Health Organization and FIND convened a development group of 40 leading scientists, experts, public health officials and regulators. We held a public consultation to which 27 individuals or organizations responded. The product profile calls for rapid diagnostic test readers that at minimum should: (i) interpret colorimetric tests with at least 95% agreement with expert visual interpretation; and (ii) automatically report results and associated data for the health programme. Optimally, readers should: (i) provide at least 98% agreement; (ii) operate with multiple models of rapid diagnostic tests; (iii) assist the user in performing each rapid diagnostic test according to the test instructions; and (iv) offer multiple configurations, operating modes and languages to suit the needs of diverse users, settings and health programmes.

Bien que les tests à flux latéral possèdent l'avantage d'une interprétation visuelle sans nécessiter de matériel, automatiser la lecture des tests de diagnostic rapide favorise la bonne réalisation du test, mais aussi l'interprétation et la communication des résultats. Nous avons donc créé un profil de produit cible qui détaille les caractéristiques minimales et optimales de plusieurs lecteurs de tests de diagnostic rapide. Ce profil de produit vise à promouvoir le développement de lecteurs de tests de diagnostic rapide efficaces, utiles et durables, à même de contribuer aux programmes de santé à travers le monde. Il peut s'agir d'un dispositif logiciel ou matériel sur mesure, fonctionnant sur un appareil mobile ordinaire, à usage professionnel ou non professionnel, et à des fins médicales ou non médicales. Lors de la mise au point du profil de produit, l'Organisation mondiale de la Santé et la Fondation FIND ont réuni un groupe de développement composé de 40 éminents scientifiques, experts, régulateurs et responsables de la santé publique. Nous avons lancé une consultation publique, à laquelle 27 individus ou organisations ont donné suite. D'après le profil de produit, les lecteurs de tests de diagnostic rapide doivent au minimum: (i) interpréter les tests colorimétriques présentant au moins 95% de concordance avec l'interprétation visuelle des experts et (ii) communiquer automatiquement les résultats et les données associées au programme de santé. Idéalement, ces lecteurs doivent: (i) offrir un taux de concordance égal ou supérieur à 98%, (ii) être compatibles avec plusieurs modèles de tests de diagnostic rapide, (iii) aider l'utilisateur à mener chaque test de diagnostic rapide conformément aux instructions et enfin, (iv) proposer de multiples configurations, modes opératoires et langues afin de répondre aux besoins d'un large spectre d'utilisateurs, de lieux et de programmes de santé.

Mientras que la interpretación visual sin equipos es una ventaja de las pruebas inmunocromatográficas de flujo lateral, la automatización de la medición de las pruebas de diagnóstico rápido favorece la correcta realización, interpretación y comunicación de los resultados. Hemos creado un perfil de productos objetivo que describe las características mínimas y óptimas de diversos evaluadores de pruebas de diagnóstico rápido. El objetivo del perfil de producto es promover el desarrollo de evaluadores de pruebas de diagnóstico rápido eficaces, útiles y sostenibles en apoyo de los programas sanitarios de todo el mundo. Estos evaluadores pueden ser de equipo o de programas informáticos personalizados que funcionen en un dispositivo móvil de uso general, para uso profesional o no profesional, y con fines médicos o no médicos. Durante la elaboración del perfil de producto, la Organización Mundial de la Salud y FIND convocaron a un grupo de desarrollo integrado por 40 prestigiosos científicos, expertos, funcionarios de salud pública y reguladores. Celebramos una consulta pública a la que respondieron 27 personas u organizaciones. El perfil de producto exige evaluadores de pruebas de diagnóstico rápido que, como mínimo, deben: (i) interpretar las pruebas colorimétricas con una concordancia de al menos el 95% con la interpretación visual de expertos e (ii) informar automáticamente los resultados y los datos asociados para el programa sanitario. De manera óptima, los evaluadores deberían: (i) proporcionar una concordancia de al menos el 98%, (ii) funcionar con múltiples modelos de pruebas de diagnóstico rápido, (iii) ayudar al usuario a realizar cada prueba de diagnóstico rápido según las instrucciones de la prueba, y (iv) ofrecer múltiples configuraciones, modos de funcionamiento e idiomas para adaptarse a las necesidades de diversos usuarios, entornos y programas sanitarios.

Developing target product profiles for Neisseria gonorrhoeae diagnostics in the context of antimicrobial resistance: An expert consensus.

BACKGROUND: There is a need for a rapid diagnostic point of care test to detect Neisseria gonorrhoeae (NG) infection to prevent incorrect, lack or excess of treatment resulting from current syndromic management in low-resource settings. An assay to identify NG antimicrobial resistance (AMR) is also highly desirable to facilitate antibiotic stewardship. Here we describe the development of two target product profiles (TPPs): one for a test for etiological diagnosis of NG and Chlamydia trachomatis (CT) (TPP1) and one for the detection of NG AMR/susceptibility (TPP2). METHODS: Draft TPPs were initially developed based on a landscape analysis of existing diagnostics and expert input. TPPs were refined via an online Delphi survey with two rounds of input from 68 respondents. TPP characteristics on which <75% of non-industry respondents agreed were further discussed and revised by an expert working group. RESULTS: The need for a test to identify NG in patients with urethral or vaginal discharge was identified as a minimal requirement of TPP1, with a test that can diagnose NG in asymptomatic patients as the optimal requirement. A sensitivity of 80% was considered acceptable, either in context of syndromic management or screening high-risk populations. For TPP2, the agreed minimal requirement was for a test to be used at level 2 healthcare facilities and above, with an optimal requirement of level 1 or above. A lateral flow format was preferred for TPP1, while it was considered likely that TPP2 would require a molecular format. A total of 31 test characteristics were included in TPP1 and 27 in TPP2. CONCLUSIONS: Following the working group revisions, TPPs were posted online for public feedback for two months, and are now finalized. The final TPPs are currently guiding the development of new diagnostics that meet the defined characteristics to reach the market within two years.

Electronic clinical decision support algorithms incorporating point-of-care diagnostic tests in low-resource settings: a target product profile.

Health workers in low-resource settings often lack the support and tools to follow evidence-based clinical recommendations for diagnosing, treating and managing sick patients. Digital technologies, by combining patient health information and point-of-care diagnostics with evidence-based clinical protocols, can help improve the quality of care and the rational use of resources, and save patient lives. A growing number of electronic clinical decision support algorithms (CDSAs) on mobile devices are being developed and piloted without evidence of safety or impact. Here, we present a target product profile (TPP) for CDSAs aimed at guiding preventive or curative consultations in low-resource settings. This document will help align developer and implementer processes and product specifications with the needs of end users, in terms of quality, safety, performance and operational functionality. To identify the characteristics of CDSAs, a multidisciplinary group of experts (academia, industry and policy makers) with expertise in diagnostic and CDSA development and implementation in low-income and middle-income countries were convened to discuss a draft TPP. The TPP was finalised through a Delphi process to facilitate consensus building. An agreement greater than 75% was reached for all 40 TPP characteristics. In general, experts were in overwhelming agreement that, given that CDSAs provide patient management recommendations, the underlying clinical algorithms should be human-interpretable and evidence-based. Whenever possible, the algorithm's patient management output should take into account pretest disease probabilities and likelihood ratios of clinical and diagnostic predictors. In addition, validation processes should at a minimum show that CDSAs are implementing faithfully the evidence they are based on, and ideally the impact on patient health outcomes. In terms of operational needs, CDSAs should be designed to fit within clinic workflows and function in connectivity-challenged and high-volume settings. Data collected through the tool should conform to local patient privacy regulations and international data standards.

Target Product Profile for a Diagnostic Assay to Differentiate between Bacterial and Non-Bacterial Infections and Reduce Antimicrobial Overuse in Resource-Limited Settings: An Expert Consensus.

Acute fever is one of the most common presenting symptoms globally. In order to reduce the empiric use of antimicrobial drugs and improve outcomes, it is essential to improve diagnostic capabilities. In the absence of microbiology facilities in low-income settings, an assay to distinguish bacterial from non-bacterial causes would be a critical first step. To ensure that patient and market needs are met, the requirements of such a test should be specified in a target product profile (TPP). To identify minimal/optimal characteristics for a bacterial vs. non-bacterial fever test, experts from academia and international organizations with expertise in infectious diseases, diagnostic test development, laboratory medicine, global health, and health economics were convened. Proposed TPPs were reviewed by this working group, and consensus characteristics were defined. The working group defined non-severely ill, non-malaria infected children as the target population for the desired assay. To provide access to the most patients, the test should be deployable to community health centers and informal health settings, and staff should require <2 days of training to perform the assay. Further, given that the aim is to reduce inappropriate antimicrobial use as well as to deliver appropriate treatment for patients with bacterial infections, the group agreed on minimal diagnostic performance requirements of >90% and >80% for sensitivity and specificity, respectively. Other key characteristics, to account for the challenging environment at which the test is targeted, included: i) time-to-result <10 min (but maximally <2 hrs); ii) storage conditions at 0-40°C, ≤90% non-condensing humidity with a minimal shelf life of 12 months; iii) operational conditions of 5-40°C, ≤90% non-condensing humidity; and iv) minimal sample collection needs (50-100µL, capillary blood). This expert approach to define assay requirements for a bacterial vs. non-bacterial assay should guide product development, and enable targeted and timely efforts by industry partners and academic institutions.

Understanding history, philanthropy and the role of WHO in provision of assistive technologies for hearing loss.

UNLABELLED: Philanthropy continues to play an important role in provision of hearing devices and is often the only alternative for the majority of those in need of these devices. While this leads to improved access to services it may also create unsustainable service delivery models. Over the past decade, World Health Organization (WHO) has been making consistent efforts towards promoting accessibility and affordability of high-quality hearing devices, especially in Low- and Middle-Income Countries (LMIC). WHO developed and updated the "Guidelines for Hearing Aids and Services in Developing Countries", in 2004. In 2006, WHO supported the establishment of "World Wide (WW) Hearing", to promote hearing aid access across the globe. In the past year, WHO has renewed these efforts. As the first step and following a consultation on promoting access to hearing devices, WHO has developed a preferred product profile in order to facilitate the development and access of appropriate and affordable hearing aids for developing countries. The Convention on the Rights of Persons with Disabilities (article 32), calls for international collaboration to promote access to assistive technology including hearing devices. A coordinated global effort is required to promote availability and affordability of high-quality hearing devices. Such an undertaking requires the cooperation of all stakeholders: WHO, Member States, Non-Governmental Organizations (NGOs), philanthropists, manufacturers and users, to fulfill the international obligation and bring about a change in the quality of life of millions of people with hearing loss. IMPLICATIONS FOR REHABILITATION: Development of preferred product profile for hearing aids in LMICs can improve development and provision of high-quality, affordable hearing devices. Investment made by the recipients, such as partial financial contribution towards the cost of device or through purchase of ear mould or batteries, leads to a greater sense of responsibility towards the device and its maintenance. Low level of awareness about hearing loss and the potential benefits of hearing aids contribute to the underutilization of hearing aids.

Electrospun polyurethane-core and gelatin-shell coaxial fibre coatings for miniature implantable biosensors.

The aim of this study was to introduce bioactivity to the electrospun coating for implantable glucose biosensors. Coaxial fibre membranes having polyurethane as the core and gelatin as the shell were produced using a range of polyurethane concentrations (2, 4, 6 and 8% wt/v) while keeping gelatin concentration (10% wt/v) constant in 2,2,2-trifluoroethanol. The gelatin shell was stabilized using glutaraldehyde vapour. The formation of core-shell structure was confirmed using transmission/scanning electron microscopy and FTIR. The coaxial fibre membranes showed uniaxial tensile properties intermediate to that of the pure polyurethane and the gelatin fibre membranes. The gelatin shell increased hydrophilicity and glucose transport flux across the coaxial fibre membranes. The coaxial fibre membranes having small fibre diameter (541 nm) and a thick gelatin shell (52%) did not affect the sensor sensitivity, but decreased sensor's linearity in the long run. In contrast, thicker coaxial fibre membranes (1133 nm) having a thin gelatin shell (34%) maintained both sensitivity and linearity for the 84 days of the study period. To conclude, polyurethane-gelatin coaxial fibre membranes, due to their faster permeability to glucose, tailorable mechanical properties and bioactivity, are potential candidates for coatings to favourably modify the host responses to extend the reliable in vivo lifetime of implantable glucose biosensors.

Tailored fibro-porous structure of electrospun polyurethane membranes, their size-dependent properties and trans-membrane glucose diffusion.

The aim of this study was to develop polyurethane (PU) based fibro-porous membranes and to investigate the size-effect of hierarchical porous structure on permeability and surface properties of the developed electrospun membranes. Non-woven Selectophore™ PU membranes having tailored fibre diameters, pore sizes, and thickness were spun using electrospinning, and their chemical, physical and glucose permeability properties were characterised. Solvents, solution concentration, applied voltage, flow rate and distance to collector, each were systematically investigated, and electrospinning conditions for tailoring fibre diameters were identified. Membranes having average fibre diameters - 347, 738 and 1102 nm were characterized, revealing average pore sizes of 800, 870 and 1060 nm and pore volumes of 44, 63 and 68% respectively. Hydrophobicity increased with increasing fibre diameter and porosity. Effective diffusion coefficients for glucose transport across the electrospun membranes varied as a function of thickness and porosity, indicating high flux rates for mass transport. Electrospun PU membranes having significantly high pore volumes, extensively interconnected porosity and tailorable properties compared to conventional solvent cast membranes can find applications as coatings for sensors requiring analyte exchange.

Electrospun fibro-porous polyurethane coatings for implantable glucose biosensors.

This study reports methods for coating miniature implantable glucose biosensors with electrospun polyurethane (PU) membranes, their effects on sensor function and efficacy as mass-transport limiting membranes. For electrospinning fibres directly on sensor surface, both static and dynamic collector systems, were designed and tested. Optimum collector configurations were first ascertained by FEA modelling. Both static and dynamic collectors allowed complete covering of sensors, but it was the dynamic collector that produced uniform fibro-porous PU coatings around miniature ellipsoid biosensors. The coatings had random fibre orientation and their uniform thickness increased linearly with increasing electrospinning time. The effects of coatings having an even spread of submicron fibre diameters and sub-100 µm thicknesses on glucose biosensor function were investigated. Increasing thickness and fibre diameters caused a statistically insignificant decrease in sensor sensitivity for the tested electrospun coatings. The sensors' linearity for the glucose detection range of 2-30 mM remained unaffected. The electrospun coatings also functioned as mass-transport limiting membranes by significantly increasing the linearity, replacing traditional epoxy-PU outer coating. To conclude, electrospun coatings, having controllable fibro-porous structure and thicknesses, on miniature ellipsoid glucose biosensors were demonstrated to have minimal effect on pre-implantation sensitivity and also to have mass-transport limiting ability.

Fully integrated biochip platforms for advanced healthcare.

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications.

Review of two decades of cholera diagnostics--how far have we really come?

BACKGROUND: Cholera, an ancient scourge, continues to inflict high rates of mortality today. The rising incidence of epidemics in areas of poor sanitation and crowding highlight the need for better epidemic prevention and early response. Such interventions require the availability of rapid and accurate diagnostic techniques to trigger timely response and mitigate the scale of the outbreak. The current gold standard of bacterial culture is inadequate for rapid diagnosis, highlighting the overarching neglect of field diagnostic needs. This paper was written to support the World Health Organisation's Global Task Force on Cholera Control mandated Cholera and diarrhoeal disease laboratory Network (CholdiNet) in devising a protocol for the validation of Rapid Diagnostic Tests (RDTs) for Vibrio cholerae. The status of diagnostic tools for Vibrio cholerae is assessed, describing products that have been commercialised over the last two decades and discussing their peer-reviewed evaluation. METHOD: Review of post-1990 peer-reviewed and grey literature on rapid diagnostic tests for Vibrio cholerae. RESULTS: Since 1990, twenty four diagnostic tests have been developed for the detection of Vibrio cholerae in human faecal samples. Fourteen of these have also been described in the literature, with rapid chromatographic-immuno assays (CIA) featuring strongly. Polymerase chain reaction (PCR) assays maintain the ability to detect the lowest amount of bacteria; however CIAs achieve both low detection thresholds and high sensitivity and specificity, making them possible candidates for use in field conditions. Field and laboratory studies were performed in a wide range of settings demonstrating variability in performance, however only a few of these studies were sufficiently stringent, highlighting five RDTs that showed promise in field conditions; COAT, IP cholera dipstick, SMART, IP dipstick and Medicos. In light of non-independent reporting, the authors would like to see these five products undergoing additional studies, with further technical improvements if needed and commercial production. The authors hope that public health use of such a RDT in limited-resource field conditions on stool samples may contribute to effective reduction in cholera epidemic spread.

A critical review of glucose biosensors based on carbon nanomaterials: carbon nanotubes and graphene.

There has been an explosion of research into the physical and chemical properties of carbon-based nanomaterials, since the discovery of carbon nanotubes (CNTs) by Iijima in 1991. Carbon nanomaterials offer unique advantages in several areas, like high surface-volume ratio, high electrical conductivity, chemical stability and strong mechanical strength, and are thus frequently being incorporated into sensing elements. Carbon nanomaterial-based sensors generally have higher sensitivities and a lower detection limit than conventional ones. In this review, a brief history of glucose biosensors is firstly presented. The carbon nanotube and grapheme-based biosensors, are introduced in Sections 3 and 4, respectively, which cover synthesis methods, up-to-date sensing approaches and nonenzymatic hybrid sensors. Finally, we briefly outline the current status and future direction for carbon nanomaterials to be used in the sensing area.

Implantable enzyme amperometric biosensors.

The implantable enzyme amperometric biosensor continues as the dominant in vivo format for the detection, monitoring and reporting of biochemical analytes related to a wide range of pathologies. Widely used in animal studies, there is increasing emphasis on their use in diabetes care and management, the management of trauma-associated hemorrhage and in critical care monitoring by intensivists in the ICU. These frontier opportunities demand continuous indwelling performance for up to several years, well in excess of the currently approved seven days. This review outlines the many challenges to successful deployment of chronically implantable amperometric enzyme biosensors and emphasizes the emerging technological approaches in their continued development. The foreign body response plays a prominent role in implantable biotransducer failure. Topics considering the approaches to mitigate the inflammatory response, use of biomimetic chemistries, nanostructured topographies, drug eluting constructs, and tissue-to-device interface modulus matching are reviewed. Similarly, factors that influence biotransducer performance such as enzyme stability, substrate interference, mediator selection and calibration are reviewed. For the biosensor system, the opportunities and challenges of integration, guided by footprint requirements, the limitations of mixed signal electronics, and power requirements, has produced three systems approaches. The potential is great. However, integration along the multiple length scales needed to address fundamental issues and integration across the diverse disciplines needed to achieve success of these highly integrated systems, continues to be a challenge in the development and deployment of implantable amperometric enzyme biosensor systems.

Nano-yarn carbon nanotube fiber based enzymatic glucose biosensor.

A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 microm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 degrees C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 microM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.

A dexamethasone-loaded PLGA microspheres/collagen scaffold composite for implantable glucose sensors.

We have developed a new dexamethasone (Dex)-loaded poly(lactic-co-glycolic acid) microspheres/porous collagen scaffold composite for implantable glucose sensors. The scaffolds were fabricated around the sensing element of the sensors and crosslinked using nordihydroguaiaretic acid (NDGA). The microspheres containing Dex were incorporated into the NDGA-crosslinked collagen scaffold by dipping in microsphere suspension in either water or Pluronic. The loading efficiencies of Dex in the microspheres and the scaffold were determined using high performance liquid chromatography. The microspheres/scaffold composite fabricated using microspheres in the hydrogel solution had a better loading efficiency than when microspheres were in water suspension. The composite fabricated using the hydrogel also showed a slower and more sustained drug release than the standard microspheres in vitro during a 4 week study and did not significantly affect the function of the sensors in vitro. The sensors with the composite that were still functional retained above 50% of their original sensitivity at 2 weeks. Histology showed that the inflammatory response to the Dex-loaded composite was much lower than for the control scaffold at 2 and 4 weeks after implantation. The Dex-loaded composite system might be useful to reduce inflammation to implanted glucose sensors and therefore extend their function and lifetime.