FORWARD Study of GORE VIABAHN Balloon-Expandable Endoprostheses and Bare Metal Stents in the United States, European Union, United Kingdom, Australia, and New Zealand When Placed to Treat Complex Iliac Occlusive Disease: Protocol for a Randomized Superiority Trial.

BACKGROUND: The recommendations for the use of and selection of covered stent grafts in patients with aortoiliac occlusive disease are limited. OBJECTIVE: The GORE VBX FORWARD clinical study aims to demonstrate the superiority of the GORE VIABAHN VBX Balloon Expandable Endoprosthesis (VBX device) for primary patency when compared to bare metal stenting (BMS) for the treatment of complex iliac artery occlusive disease. METHODS: A prospective, multicenter, randomized control study in the United States, European Union, United Kingdom, Australia, and New Zealand will enroll patients with symptomatic, complex iliac artery occlusive disease. In this study, iliac artery occlusive disease is defined as a unilateral or bilateral disease with single or multiple lesions (with >50% stenosis or chronic total occlusion) each between 4 and 11 cm in length. In an attempt to more closely match real-world practices, patients with minor tissue loss (Rutherford class 5) and patients requiring hemodialysis will be included. Baseline aortoiliac angiography will be performed to assess target lesion characteristics and determine final patient eligibility. Once the patient is confirmed and guidewires are in place across the target lesions, the patient will be randomized in a 1:1 format to treatment with either the VBX device or a BMS. The BMS can be balloon- or self-expanding and must be approved for the iliac artery occlusive disease indication. Patients, the independent core laboratory reviewers, and Clinical Events Committee members will be blinded from the assigned treatment. Dual antithrombotic medical therapy is required through a minimum of 3 months post procedure. The primary end point is 12­month primary patency and will be adjudicated by an independent imaging core laboratory and Clinical Events Committee. Key secondary end points will be tested for superiority and include technical, acute procedural, and clinical success; changes in Ankle-brachial index; patient quality of life; primary patency; freedom from restenosis; primary-assisted patency; secondary patency; freedom from target lesion revascularizations; cumulative reintervention rate; amputation-free survival; survival; and change in Rutherford category. Study follow-up will continue through 5 years. RESULTS: Outcomes will be reported following study completion. Enrollment is anticipated to start in October 2023. CONCLUSIONS: The results of this study will provide definitive, level 1 clinical evidence to clinicians on the optimal choice of stent device to use for the treatment of complex iliac artery occlusive disease. The FORWARD study is powered for superiority and includes only complex, unilateral, or bilateral lesions involving the common or external iliac arteries. This study is a multidisciplinary endeavor involving vascular surgery, interventional cardiology, and interventional radiology across multiple countries with a blinded core laboratory review of end points in hopes that the outcomes will be widely accepted and incorporated into practice guidelines for optimal treatment of patients with complex iliac artery occlusive disease. TRIAL REGISTRATION: ClinicalTrials.gov NCT05811364; https://clinicaltrials.gov/study/NCT05811364. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/51480.

Multiplexed Recombinase Polymerase Amplification Assay To Detect Intestinal Protozoa.

This work describes a proof-of-concept multiplex recombinase polymerase amplification (RPA) assay with lateral flow readout that is capable of simultaneously detecting and differentiating DNA from any of the diarrhea-causing protozoa Giardia, Cryptosporidium, and Entamoeba. Together, these parasites contribute significantly to the global burden of diarrheal illness. Differential diagnosis of these parasites is traditionally accomplished via stool microscopy. However, microscopy is insensitive and can miss up to half of all cases. DNA-based diagnostics such as polymerase chain reaction (PCR) are far more sensitive; however, they rely on expensive thermal cycling equipment, limiting their availability to centralized reference laboratories. Isothermal DNA amplification platforms, such as the RPA platform used in this study, alleviate the need for thermal cycling equipment and have the potential to broaden access to more sensitive diagnostics. Until now, multiplex RPA assays have not been developed that are capable of simultaneously detecting and differentiating infections caused by different pathogens. We developed a multiplex RPA assay to detect the presence of DNA from Giardia, Cryptosporidium, and Entamoeba. The multiplex assay was characterized using synthetic DNA, where the limits-of-detection were calculated to be 403, 425, and 368 gene copies per reaction of the synthetic Giardia, Cryptosporidium, and Entamoeba targets, respectively (roughly 1.5 orders of magnitude higher than for the same targets in a singleplex RPA assay). The multiplex assay was also characterized using DNA extracted from live parasites spiked into stool samples where the limits-of-detection were calculated to be 444, 6, and 9 parasites per reaction for Giardia, Cryptosporidium, and Entamoeba parasites, respectively. This proof-of-concept assay may be reconfigured to detect a wide variety of targets by re-designing the primer and probe sequences.

All-plastic miniature fluorescence microscope for point-of-care readout of bead-based bioassays.

A number of new platforms have been developed for multiplexed bioassays that rely on imaging targeted fluorescent beads labeled with different fluorescent dyes. We developed a compact, low-cost three-dimensional printed fluorescence microscope that can be used as a detector for mutiplexed, bead-based assays to support point-of-care applications. Images obtained with the microscope were analyzed to differentiate multiple analytes in a single sample with a comparable limit of detection to commercially available macroscopic assay platforms.

Detection of Entamoeba histolytica by Recombinase Polymerase Amplification.

Amebiasis is an important cause of diarrheal disease worldwide and has been associated with childhood malnutrition. Traditional microscopy approaches are neither sensitive nor specific for Entamoeba histolytica. Antigen assays are more specific, but many cases are missed unless tested by molecular methods. Although polymerase chain reaction (PCR) is effective, the need for sophisticated, expensive equipment, infrastructure, and trained personnel limits its usefulness, especially in the resource-limited, endemic areas. Here, we report development of a recombinase polymerase amplification (RPA) method to detect E. histolytica specifically. Using visual detection by lateral flow (LF), the test was highly sensitive and specific and could be performed without additional equipment. The availability of this inexpensive, sensitive, and field-applicable diagnostic test could facilitate rapid diagnosis and treatment of amebiasis in endemic regions.

Development of a quantitative recombinase polymerase amplification assay with an internal positive control.

It was recently demonstrated that recombinase polymerase amplification (RPA), an isothermal amplification platform for pathogen detection, may be used to quantify DNA sample concentration using a standard curve. In this manuscript, a detailed protocol for developing and implementing a real-time quantitative recombinase polymerase amplification assay (qRPA assay) is provided. Using HIV-1 DNA quantification as an example, the assembly of real-time RPA reactions, the design of an internal positive control (IPC) sequence, and co-amplification of the IPC and target of interest are all described. Instructions and data processing scripts for the construction of a standard curve using data from multiple experiments are provided, which may be used to predict the concentration of unknown samples or assess the performance of the assay. Finally, an alternative method for collecting real-time fluorescence data with a microscope and a stage heater as a step towards developing a point-of-care qRPA assay is described. The protocol and scripts provided may be used for the development of a qRPA assay for any DNA target of interest.

Recombinase polymerase amplification-based assay to diagnose Giardia in stool samples.

Giardia duodenalis is one of the most commonly identified parasites in stool samples. Although relatively easy to treat, giardiasis can be difficult to detect as it presents similar to other diarrheal diseases. Here, we present a recombinase polymerase amplification-based Giardia (RPAG) assay to detect the presence of Giardia in stool samples. The RPAG assay was characterized on the bench top using stool samples spiked with Giardia cysts where it showed a limit-of-detection nearly as low as the gold standard polymerase chain reaction assay. The RPAG assay was then tested in the highlands of Peru on 104 stool samples collected from the surrounding communities where it showed 73% sensitivity and 95% specificity against a polymerase chain reaction and microscopy composite gold standard. Further improvements in clinical sensitivity will be needed for the RPAG assay to have clinical relevance.

Equipment-free incubation of recombinase polymerase amplification reactions using body heat.

The development of isothermal amplification platforms for nucleic acid detection has the potential to increase access to molecular diagnostics in low resource settings; however, simple, low-cost methods for heating samples are required to perform reactions. In this study, we demonstrated that human body heat may be harnessed to incubate recombinase polymerase amplification (RPA) reactions for isothermal amplification of HIV-1 DNA. After measuring the temperature of mock reactions at 4 body locations, the axilla was chosen as the ideal site for comfortable, convenient incubation. Using commonly available materials, 3 methods for securing RPA reactions to the body were characterized. Finally, RPA reactions were incubated using body heat while control RPA reactions were incubated in a heat block. At room temperature, all reactions with 10 copies of HIV-1 DNA and 90% of reactions with 100 copies of HIV-1 DNA tested positive when incubated with body heat. In a cold room with an ambient temperature of 10 degrees Celsius, all reactions containing 10 copies or 100 copies of HIV-1 DNA tested positive when incubated with body heat. These results suggest that human body heat may provide an extremely low-cost solution for incubating RPA reactions in low resource settings.

Quantification of HIV-1 DNA using real-time recombinase polymerase amplification.

Although recombinase polymerase amplification (RPA) has many advantages for the detection of pathogenic nucleic acids in point-of-care applications, RPA has not yet been implemented to quantify sample concentration using a standard curve. Here, we describe a real-time RPA assay with an internal positive control and an algorithm that analyzes real-time fluorescence data to quantify HIV-1 DNA. We show that DNA concentration and the onset of detectable amplification are correlated by an exponential standard curve. In a set of experiments in which the standard curve and algorithm were used to analyze and quantify additional DNA samples, the algorithm predicted an average concentration within 1 order of magnitude of the correct concentration for all HIV-1 DNA concentrations tested. These results suggest that quantitative RPA (qRPA) may serve as a powerful tool for quantifying nucleic acids and may be adapted for use in single-sample point-of-care diagnostic systems.

Nucleic acid test to diagnose cryptosporidiosis: lab assessment in animal and patient specimens.

Diarrheal diseases cause more morbidity and mortality around the world than human immunodeficiency virus (HIV), malaria, or tuberculosis. Given that effective treatment of persistent diarrheal illness requires knowledge of the causative organism, diagnostic tests are of paramount importance. The protozoan parasites of the genus Cryptosporidium are increasingly recognized to be responsible for a significant portion of diarrhea morbidity. We present a novel nucleic acid test to detect the presence of Cryptosporidium species in DNA extracted from stool samples. The assay uses the isothermal amplification technique recombinase polymerase amplification (RPA) to amplify trace amounts of pathogen DNA extracted from stool to detectable levels in 30 min; products are then detected visually on simple lateral flow strips. The RPA-based Cryptosporidium assay (RPAC assay) was developed and optimized using DNA from human stool samples spiked with pathogen. It was then tested using DNA extracted from the stool of infected mice where it correctly identified the presence or absence of 27 out of 28 stool samples. It was finally tested using DNA extracted from the stool of infected patients where it correctly identified the presence or absence of 21 out of 21 stool samples. The assay was integrated into a foldable, paper and plastic device that enables DNA amplification with only the use of pipets, pipet tips, and a heater. The performance of the integrated assay is comparable to or better than polymerase chain reaction (PCR), without requiring the use of thermal cycling equipment. This platform can easily be adapted to detect DNA from multiple pathogens.