Use of rapid diagnostic tests for diagnosis of malaria in the UK

BACKGROUND: Malaria is currently diagnosed almost exclusively by microscopy in clinical laboratories. The introduction of rapid diagnostic tests (RDTs) may be useful in achieving rapid detection of malaria parasites, especially in situations where malaria is not often seen or where staff are inexperienced. AIM: To explore the use of RDT in UK laboratories. METHODS: The current use of RDTs was surveyed in UK laboratories subscribing to the United Kingdom National External Quality Assessment Scheme blood parasitology and haematology schemes. RESULTS: An overall survey response rate of 60.3% was seen. RDTs were found to be the preferred choice, either alone or in conjunction with microscopy in 31.2% of the samples examined during normal working hours and in 44.3% of the specimens examined on call. CONCLUSIONS: During on-call hours, the use of RDTs was observed to increase and RDTs changed the diagnosis in 12% of laboratories. No established protocol for RDT use was, however, observed in the UK. A protocol that needs to be validated in the laboratory setting is suggested.     

Rapid diagnostic tests for infectious diseases in the emergency department

BackgroundRapid diagnostic tests (RDTs) for infectious diseases, with a turnaround time of less than 2 hours, are promising tools that could improve patient care, antimicrobial stewardship and infection prevention in the emergency department (ED) setting. Numerous RDTs have been developed, although not necessarily for the ED environment. Their successful implementation in the ED relies on their performance and impact on patient management.ObjectivesThe aim of this narrative review was to provide an overview of currently available RDTs for infectious diseases in the ED.SourcesPubMed was searched through August 2019 for available studies on RDTs for infectious diseases. Inclusion criteria included: commercial tests approved by the US Food and Drug Administration (FDA) or Conformité Européenne (CE) in vitro diagnostic devices with data on clinical samples, ability to run on fully automated systems and result delivery within 2 hours.ContentA nonexhaustive list of representative commercially available FDA- or CE-approved assays was categorized by clinical syndrome: pharyngitis and upper respiratory tract infection, lower respiratory tract infection, gastrointestinal infection, meningitis and encephalitis, fever in returning travellers and sexually transmitted infection, including HIV. The performance of tests was described on the basis of clinical validation studies. Further, their impact on clinical outcomes and anti-infective use was discussed with a focus on ED-based studies.ImplicationsClinicians should be familiar with the distinctive features of each RDT and individual performance characteristics for each target. Their integration into ED work flow should be preplanned considering local constraints of given settings. Additional clinical studies are needed to further evaluate their clinical effectiveness and cost-effectiveness.     

Limited Level of Accuracy Provided by Available Rapid Diagnosis Tests for Malaria Enhances the Need for PCR-Based Reference Laboratories

The rise of imported malaria cases and the high fatality rate in Europe make the search for new and easy diagnostic methods necessary. Rapid diagnosis tests (RDTs) are, in part, developed to cover the lack of diagnosis experience. Unfortunately, our data suggest that the accuracy of RDTs is insufficient and could increase the number of incorrect malaria diagnoses.     

Comparative Evaluation of 11 Commercialized Rapid Diagnostic Tests for Detecting Trypanosoma cruzi Antibodies in Serum Banks in Areas of Endemicity and Nonendemicity

Chagas disease is one of the main public health issues in Latin America. Increasingly during the past few decades, Trypanosoma cruzi infection has been detected in North America, Europe, and the Western Pacific, mainly as a result of population movement. The limited availability of rapid serological diagnostic tests hinders rapid diagnosis and early treatment in areas of endemicity and nonendemicity. In collaboration with 11 national reference laboratories (NRLs) from different geographical areas, we evaluated the performances of commercialized serological rapid diagnostic tests (RDT) for T. cruzi infection. Eleven commercialized T. cruzi infection RDTs were evaluated on a total of 474 samples extensively tested with at least three different techniques for Chagas disease, maintained at controlled low temperatures, and stored in the serum banks of the 11 NRLs. We measured the sensitivity, specificity, and concordance of each RDT and provided an additional questionnaire to evaluate its ease of use. The selected RDTs in this study were performed under controlled laboratory conditions. Out of the 11 RDTs, we found 8 of them to be useful, with the cassette format favored over the strip. We did not observe significant differences in RDT performances in the different regions. Overall, the performance results were lower than those disclosed by the manufacturers. The results of this evaluation validate the possibility of using RDTs to diagnose Chagas disease, thereby decreasing the time to treatment at a primary health care facility for patients who are willing to be treated. Further studies should be conducted in the laboratory and in the field to confirm these data, expressly to evaluate reproducibility in resource-limited settings, or using whole blood in clinical settings in areas of endemicity and nonendemicity.     

Malaria rapid diagnostic tests in elimination settings—can they find the last parasite?

Rapid diagnostic tests (RDTs) for malaria have improved the availability of parasite-based diagnosis throughout the malaria-endemic world. Accurate malaria diagnosis is essential for malaria case management, surveillance, and elimination. RDTs are inexpensive, simple to perform, and provide results in 15-20 min. Despite high sensitivity and specificity for Plasmodium falciparum infections, RDTs have several limitations that may reduce their utility in low-transmission settings: they do not reliably detect low-density parasitaemia (≤200 parasites/μL), many are less sensitive for Plasmodium vivax infections, and their ability to detect Plasmodium ovale and Plasmodium malariae is unknown. Therefore, in elimination settings, alternative tools with higher sensitivity for low-density infections (e.g. nucleic acid-based tests) are required to complement field diagnostics, and new highly sensitive and specific field-appropriate tests must be developed to ensure accurate diagnosis of symptomatic and asymptomatic carriers. As malaria transmission declines, the proportion of low-density infections among symptomatic and asymptomatic persons is likely to increase, which may limit the utility of RDTs. Monitoring malaria in elimination settings will probably depend on the use of more than one diagnostic tool in clinical-care and surveillance activities, and the combination of tools utilized will need to be informed by regular monitoring of test performance through effective quality assurance.     

Update on rapid diagnostic testing for malaria

To help mitigate the expanding global impact of malaria, with its associated increasing drug resistance, implementation of prompt and accurate diagnosis is needed. Malaria is diagnosed predominantly by using clinical criteria, with microscopy as the current gold standard for detecting parasitemia, even though it is clearly inadequate in many health care settings. Rapid diagnostic tests (RDTs) have been recognized as an ideal method for diagnosing infectious diseases, including malaria, in recent years. There have been a number of RDTs developed and evaluated widely for malaria diagnosis, but a number of issues related to these products have arisen. This review highlights RDTs, including challenges in assessing their performance, internationally available RDTs, their effectiveness in various health care settings, and the selection of RDTs for different health care systems.     

Comparative Evaluation of Blood and Serum Samples in Rapid Immunochromatographic Tests for Visceral Leishmaniasis

Rapid diagnostic tests (RDTs) based on the detection of specific antibodies in serum are commonly used for the diagnosis of visceral leishmaniasis (VL). Several commercial kits are available, and some of them allow the use of whole-blood samples instead of serum. An RDT is much more user-friendly for blood samples than for serum samples. In this study, we examined the sensitivities and specificities of six different commercially available immunochromatographic tests for their accuracy in detecting Leishmania infection in whole blood and serum of parasitologically confirmed VL cases. This study was performed in areas of India and Nepal where VL is endemic. A total of 177 confirmed VL cases, 208 healthy controls from areas of endemicity (EHCs), 26 malaria patients (MP), and 37 tuberculosis (TB) patients were enrolled. The reproducibilities of the blood and serum results and between-reader and between-laboratory results were tested. In India, the sensitivities of all the RDTs ranged between 94.7 and 100.0%, with no significant differences between whole blood and serum. The specificities ranged between 92.4 and 100.0%, except for the specificity of the Onsite Leishmania Ab RevB kit, which was lower (33.6 to 42.0%). No differences in specificities were observed for blood and serum. In Nepal, the sensitivities of all the test kits, for whole-blood as well as serum samples, ranged between 96.3 and 100.0%, and the specificities ranged between 90.1 and 96.1%, again with the exception of that of the Onsite Leishmania Ab RevB test, which was markedly lower (48.7 to 49.3%). The diagnostic accuracies of all the tests, except for one brand, were excellent for the whole-blood and serum samples. We conclude that whole blood is an adequate alternative for serum in RDTs for VL, with sensitivities and specificities comparable to those obtained in serum samples, provided that the test kit is of overall good quality.     

Notes on rapid diagnostic tests for chronic Chagas disease

A rapid diagnostic test (RDT) is a test that can quickly determine (from minutes up to 2 h) a diagnosis. It is a simple, quick, and inexpensive technique that does not require complex equipment or specialized staff. For this reason, such tests have been proposed for the diagnosis of Chagas Disease (CD), which affects populations difficult to reach, or migrants in nonendemic areas, where there is a low prevalence of the disease. With these notes we take into consideration one of the best RDTs for CD currently available on the market as an example and make some comments on its use in the field on the base of the current evidences.     

BBK07 immunodominant peptides as serodiagnostic markers of Lyme disease

Lyme disease (LD) is a tick-borne infection caused by the bacterial pathogen Borrelia burgdorferi. Current diagnostic tests mostly use borrelial lysates or select antigens to detect serum antibodies against B. burgdorferi. These immunoassays are not entirely effective, especially for detection of early infection. We have recently characterized an in vivo-induced antigen, BBK07, as a serodiagnostic marker for LD. We now report that in a line blot assay, recombinant BBK07 protein-based detection is 90% sensitive and nearly 100% specific against B. burgdorferi infection in humans. Using an overlapping peptide library of 23 peptides encompassing full-length BBK07, we identified the immunodominant epitopes of BBK07 during human infection. We show that a select combination of amino-terminal peptides significantly enhanced BBK07-based diagnostic accuracy compared to that with the full-length protein. Although in enzyme-linked immunosorbent assay (ELISA) studies BBK07 peptides had overall lower sensitivity than established serodiagnostic peptides, such as the VlsE peptide C6 and OspC peptide pepC10, for the detection of early human LD, a subset of serum samples that failed to recognize either VlsE or OspC peptides were preferentially reactive to BBK07 peptides. These results highlight the fact that BBK07 peptides could be useful to complement the efficacy of VlsE and OspC peptide-based serodiagnostic assays. Finally, using a panel of canine sera, we show that BBK07 peptide is also effective for LD diagnosis in infected dogs. Together, our data show that peptides from the B. burgdorferi surface protein BBK07 are highly specific and sensitive serodiagnostic markers, and we suggest their future use in LD diagnostic assays.     

Current strategies to avoid misdiagnosis of malaria

Malaria remains the most important parasitic disease, and tens of thousands of cases are imported into non-endemic countries annually. However, any single institution may see only a very few cases—this is probably the reason why laboratory and clinical misdiagnosis may not be uncommon. In the laboratory, unfamiliarity with microscopic diagnosis may be the main reason, considering the large number of laboratory staff who provide on-call services, often without expert help at hand, as well as the difficulty in detecting cases with low-level parasitemia. Staff should therefore be provided with continuing microscopic training to maintain proficiency. The complementary use of immunochromatographic rapid detection tests (RDTs) may be useful, especially during on-call hours, although, in order to ensure correct interpretation, their inherent limitations have to be well known. Diagnosis based on the polymerase chain reaction is still unsuitable for routine use, due to its long turnaround time, its cost, and its unavailability outside regular hours, although it may be helpful in selected cases. Once the alert clinician has considered the possibility of malaria, and suspicion continues to be high, malaria can be excluded by repeat smears or RDTs. However, the absence of clinical suspicion may not be infrequent, and may have more serious consequences. Depending on the local number of malaria cases seen, laboratory staff should have a low threshold for the decision to perform unsolicited malaria diagnostic tests on suspicious samples, especially if other laboratory tests are abnormal (e.g. thrombocytopenia, presence of atypical lymphocytes, or raised lactate dehydrogenase). The detection of intraleukocytic hemozoin during automated full blood counts is a promising new way to avoid misdiagnosis of clinically unsuspected malaria.     

Rapid diagnostic tests for non-malarial febrile illness in the tropics

The recent roll-out of rapid diagnostic tests (RDTs) for malaria has highlighted the decreasing proportion of malaria-attributable illness in endemic areas. Unfortunately, once malaria is excluded, there are few accessible diagnostic tools to guide the management of severe febrile illnesses in low resource settings. This review summarizes the current state of RDT development for several key infections, including dengue fever, enteric fever, leptospirosis, brucellosis, visceral leishmaniasis and human African trypanosomiasis, and highlights many remaining gaps. Most RDTs for non-malarial tropical infections currently rely on the detection of host antibodies against a single infectious agent. The sensitivity and specificity of host-antibody detection tests are both inherently limited. Moreover, prolonged antibody responses to many infections preclude the use of most serological RDTs for monitoring response to treatment and/or for diagnosing relapse. Considering these limitations, there is a pressing need for sensitive pathogen-detection-based RDTs, as have been successfully developed for malaria and dengue. Ultimately, integration of RDTs into a validated syndromic approach to tropical fevers is urgently needed. Related research priorities are to define the evolving epidemiology of fever in the tropics, and to determine how combinations of RDTs could be best used to improve the management of severe and treatable infections requiring specific therapy.     

Molecular genetic methods in the diagnosis of lower respiratory tract infections

Molecular diagnostic techniques, such as PCR, have become useful tools for the rapid etiological diagnosis of lower respiratory tract infections. Nucleic acid amplification tests (NAATs) have been evaluated for detecting most respiratory pathogens, and commercial assays are available for some pathogens. However, standardized protocols are needed before these assays are introduced into routine diagnostic use. For pneumonia, NAATs offer advantages over conventional tests for the detection of Mycoplasma pneumoniae, Legionella spp. and Chlamydia pneumoniae. For pneumococcal pneumonia in adults, PCR adds little to existing diagnostic tests, and is unable to distinguish pneumococcal colonization from infection when testing respiratory samples. Although less sensitive than culture-based methods, several commercial molecular diagnostic assays have been developed for tuberculosis and are useful rapid tests for selected patients. PCR can now be considered the rapid diagnostic test of choice for pertussis and some respiratory virus infections. Further work is required to better characterize the role of molecular diagnostic tests for diagnosing lower respiratory tract infections, and to develop standard assays that can be readily adopted by routine diagnostic laboratories.     

Laboratory Evaluation of Three Rapid Diagnostic Tests for Dual Detection of HIV and Treponema pallidum Antibodies

The performance of three research-use-only, dual HIV and syphilis rapid diagnostic tests (RDTs) was evaluated for 150 patient serum samples and compared to reference HIV and Treponema pallidum antibody detection methods. The RDTs performed comparably, with sensitivities of 93 to 99% and specificities of 97 to 100%. The kappa statistic between the RDTs was 0.95.     

Loop-Mediated Isothermal Amplification Assay for Rapid Diagnosis of Malaria Infections in an Area of Endemicity in Thailand

The loop-mediated isothermal amplification (LAMP) method, developed by our group for diagnosis of four human malaria parasites, was evaluated on a large scale at a remote clinic in Thailand where malaria is endemic. A total of 899 febrile patients were analyzed in this study. LAMP was first evaluated in 219 patients, and the result was compared to those of two histidine-rich protein (HRP)-2 rapid diagnostic tests (RDTs) and microscopy as a gold standard. LAMP DNA extraction was conducted by a simple boiling method, and the test results were assessed visually. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 95.7%, 100%, 100%, and 98%, respectively, for LAMP and 98.6%, 98%, 95.8%, and 99.3%, respectively, for RDTs. Since RDT-positive results were based on one out of two RDTs, the sensitivity of RDTs was slightly higher than that of LAMP. However, LAMP tended to be more specific than RDTs. LAMP next was evaluated in 680 patients, and the result was compared to that of microscopy as a gold standard. Sensitivity, specificity, PPV, NPV, and diagnostic accuracy of LAMP were 88.9%, 96.9%, 92.2%, 95.5%, and 94.6%, respectively. Nested PCR was used to confirm the discrepant results. Malaria LAMP in a remote clinic in Thailand achieved an acceptable result, indicating that LAMP malaria diagnosis is feasible in a field setting with limited technical resources. Additionally, the rapid boiling method for extracting DNA from dried blood spots proved to be simple, fast, and suitable for use in the field.     

Indirect enzyme-linked immunosorbent assay for detection of immunoglobulin G reactive with a recombinant protein expressed from the gene encoding the 116-kilodalton protein of Mycoplasma pneumoniae

Serology remains the method of choice for laboratory diagnosis of Mycoplasma pneumoniae infection. Currently available serological tests employ complex cellular fractions of M. pneumoniae as antigen. To improve the specificity of M. pneumoniae diagnosis, a recombinant protein was assessed as a serodiagnostic reagent. A panel of recombinant proteins were expressed from a cloned M. pneumoniae gene that encodes a 116-kDa surface protein antigen. The recombinant proteins were assessed for reactivity with patient sera and the most antigenic was further assessed for its serodiagnostic potential by indirect enzyme-linked immunosorbent assay (ELISA). The ELISA based on the recombinant protein was equivalent in sensitivity to the commercial test (Serodia Myco II; Fujirebio Inc.) to which it was compared. Southern and Western blotting data suggested that the recombinant protein derived from the 116-kDa protein of M. pneumoniae could provide a species-specific diagnostic tool, although further assessment is required.     

Rapid diagnostic tests for determining dengue serostatus: a systematic review and key informant interviews

ObjectivesVaccination for dengue with the live attenuated tetravalent CYD-TDV vaccine (Dengvaxia®) is only recommended in individuals who have had prior dengue virus (DENV) infection. Rapid diagnostic tests (RDT) for past DENV infection would offer a convenient method for pre-vaccination screening at point-of-care. A systematic review was conducted to evaluate the performance of current dengue RDTs for determining dengue serostatus, using IgG antibodies against DENV as a marker of past infection.MethodsPubMed and EMBASE databases were searched from 2000 to 2018 to identify studies evaluating dengue RDTs in individuals with known or possible previous DENV infection. Study quality was evaluated using GRADE and QUADAS-2 criteria. Semi-structured interviews were also performed with available dengue RDT manufacturers.ResultsThe performance of four dengue IgG RDTs was determined in 3137 individuals across ten studies conducted in 13 countries, with serum used in most of the studies. No studies reported data for determining dengue serostatus, and limited data were available regarding cross-reactivity with other viruses. The majority of studies demonstrated sensitivities and specificities between 80% and 100% for dengue IgG detection in samples from secondary infection or convalescent time-points after recent infection.ConclusionsAlthough current dengue IgG RDTs have shown reasonable performance compared with laboratory-based tests in secondary infection, additional research is needed to determine how RDTs would perform in relevant populations targeted for vaccination. New RDTs or modifications to current RDTs are feasible and may optimize the performance of these tests for use in a pre-vaccination screening approach.