Latent class analysis of diagnostic tests for visceral leishmaniasis in Brazil

Recombinant protein KR95 as an alternative for serological diagnosis of human visceral leishmaniasis in the Americas

In the Americas, visceral leishmaniasis (VL) is caused by the protozoan Leishmania infantum, leading to death if not promptly diagnosed and treated. In Brazil, the disease reaches all regions, and in 2020, 1,933 VL cases were reported with 9.5% lethality. Thus, an accurate diagnosis is essential to provide the appropriate treatment. Serological VL diagnosis is based mainly on immunochromatographic tests, but their performance may vary by location, and evaluation of diagnostic alternatives is necessary. In this study, we aimed to evaluate the performance of ELISA with the scantily studied recombinant antigens, K18 and KR95, comparing their performance with the already known rK28 and rK39. Sera from parasitologically confirmed symptomatic VL patients (n = 90) and healthy endemic controls (n = 90) were submitted to ELISA with rK18 and rKR95. Sensitivity (95% CI) was, respectively, 83.3% (74.2-89.7) and 95.6% (88.8-98.6), and specificity (95% CI) was 93.3% (85.9-97.2) and 97.8% (91.8-99.9). For validation of ELISA with the recombinant antigens, we included samples from 122 VL patients and 83 healthy controls collected in three regions in Brazil (Northeast, Southeast, and Midwest). When comparing the results obtained with the VL patients' samples, significantly lower sensitivity was obtained by rK18-ELISA (88.5%, 95% CI: 81.5-93.2) compared with rK28-ELISA (95.9%, 95% CI: 90.5-98.5), but the sensitivity was similar comparing rKR95-ELISA (95.1%, 95% CI: 89.5-98.0), rK28-ELISA (95.9%, 95% CI: 90.5-98.5), and rK39-ELISA (94.3%, 95% CI: 88.4-97.4). Analyzing the specificity, it was lowest with rK18-ELISA (62.7%, 95% CI: 51.9-72.3) with 83 healthy control samples. Conversely, higher and similar specificity was obtained by rKR95-ELISA (96.4%, 95% CI: 89.5-99.2), rK28-ELISA (95.2%, 95% CI: 87.9-98.5), and rK39-ELISA (95.2%, 95% CI: 87.9-98.5). There was no difference in sensitivity and specificity across localities. Cross-reactivity assessment, performed with sera of patients diagnosed with inflammatory disorders and other infectious diseases, was 34.2% with rK18-ELISA and 3.1% with rKR95-ELISA. Based on these data, we suggest using recombinant antigen KR95 in serological assays for VL diagnosis.

Serology for visceral leishmaniasis: How trusty is the accuracy reported by the manufacturers?

Timely and accurate diagnosis is one of the strategies for managing visceral leishmaniasis (VL). Given the specificities of this infection, which affects different vulnerable populations, the local assessment of the accuracy of the available diagnostic test is a requirement for the good use of resources. In Brazil, performance data are required for test registration with the National Regulatory Agency (ANVISA), but there are no minimum requirements established for performance evaluation. Here, we compared the accuracy reported in the manufacturer's instructions of commercially available VL-diagnostic tests in Brazil, and the accuracies reported in the scientific literature which were obtained after test commercialization. The tests were identified via the electronic database of ANVISA, and their accuracy was obtained from the manufacturer's instructions. A literature search for test accuracy was performed using two databases. A total of 28 VL diagnostic tests were identified through the ANVISA database. However, only 13 presented performance data in the manufacturer's instructions, with five immunoenzymatic tests, three indirect immunofluorescence tests, one chemiluminescence test, and four rapid tests. For most tests, the manufacturers did not provide the relevant information, such as sample size, reference standards, and study site. The literature review identified accuracy data for only 61.5% of diagnostic tests registered in Brazil. These observations confirmed that there are significant flaws in the process of registering health technologies and highlighted one of the reasons for the insufficient control of policies, namely, the use of potentially inaccurate and inappropriate diagnostic tools for a given scenario.

Bayesian latent class models for identifying canine visceral leishmaniosis using diagnostic tests in the absence of a gold standard

Background

Like many infectious diseases, there is no practical gold standard for diagnosing clinical visceral leishmaniasis (VL). Latent class modeling has been proposed to estimate a latent gold standard for identifying disease. These proposed models for VL have leveraged information from diagnostic tests with dichotomous serological and PCR assays, but have not employed continuous diagnostic test information.

Methods/Principal findings

In this paper, we employ Bayesian latent class models to improve the identification of canine visceral leishmaniasis using the dichotomous PCR assay and the Dual Path Platform (DPP) serology test. The DPP test has historically been used as a dichotomous assay, but can also yield numerical information via the DPP reader. Using data collected from a cohort of hunting dogs across the United States, which were identified as having either negative or symptomatic disease, we evaluate the impact of including numerical DPP reader information as a proxy for immune response. We find that inclusion of DPP reader information allows us to illustrate changes in immune response as a function of age.

Conclusions/Significance

Utilization of continuous DPP reader information can improve the correct discrimination between individuals that are negative for disease and those with clinical VL. These models provide a promising avenue for diagnostic testing in contexts with multiple, imperfect diagnostic tests. Specifically, they can easily be applied to human visceral leishmaniasis when diagnostic test results are available. Also, appropriate diagnosis of canine visceral leishmaniasis has important consequences for curtailing spread of disease to humans.

The increased presence of repetitive motifs in the KDDR-plus recombinant protein, a kinesin-derived antigen from Leishmania infantum, improves the diagnostic performance of serological tests for human and canine visceral leishmaniasis

Visceral leishmaniasis (VL) is caused by protozoa belonging to the Leishmania donovani complex and is considered the most serious and fatal form among the different types of leishmaniasis, if not early diagnosed and treated. Among the measures of disease control stand out the management of infected dogs and the early diagnosis and appropriate treatment of human cases. Several antigens have been characterized for use in the VL diagnosis, among them are the recombinant kinesin-derived antigens from L. infantum, as rK39 and rKDDR. The main difference between these antigens is the size of the non-repetitive kinesin region and the number of repetitions of the 39 amino acid degenerate motif (6.5 and 8.5 repeats in rK39 and rKDDR, respectively). This repetitive region has a high antigenicity score. To evaluate the effect of increasing the number of repeats on diagnostic performance, we designed the rKDDR-plus antigen, containing 15.3 repeats of the 39 amino acid degenerate motif, besides the absence of the non-repetitive portion from L. infantum kinesin. Its performance was evaluated by enzyme-linked immunosorbent assay (ELISA) and rapid immunochromatographic test (ICT), and compared with the kinesin-derived antigens (rKDDR and rK39). In ELISA with human sera, all recombinant antigens had a sensitivity of 98%, whereas the specificity for rKDDR-plus, rKDDR and rK39 was 100%, 96% and 71%, respectively. When evaluated canine sera, the ELISA sensitivity was 97% for all antigens, and the specificity for rKDDR-plus, rKDDR and rK39 was 98%, 91% and 83%, respectively. Evaluation of the ICT/rKDDR-plus, using human sera, showed greater diagnostic sensitivity (90%) and specificity (100%), when compared to the IT LEISH (79% and 98%, respectively), which is based on the rK39 antigen. These results suggest that the increased presence of repetitive motifs in the rKDDR-plus protein improves the diagnostic performance of serological tests by increasing the specificity and accuracy of the diagnosis.

Molecular Tracking of the Leishmania Parasite

With the Visceral Leishmaniasis/Kala-azar Elimination Program in South Asia in its consolidation phase, the focus is mainly on case detection, vector control, and identifying potential sources of infection. Accordingly, emphasis is presently on curbing transmission, which is potentially achievable by identification and elimination of potential reservoirs. The strongest contenders for being the disease reservoir are cases of Post Kala-azar Dermal Leishmaniasis (PKDL) which occurs in a minor proportion of individuals apparently cured of Visceral Leishmaniasis (VL). The demonstration of parasites in tissue aspirates despite being a risky and invasive process is the gold standard for diagnosis of VL, but is now being replaced by serological tests e.g., rK39 strip test and direct agglutination test. However, these antibody based tests are limited in their ability to diagnose relapses, detect cases of PKDL, and monitor effectiveness of treatment. Accordingly, detection of antigen or nucleic acids by polymerase chain reaction has been successfully applied for monitoring of parasite kinetics. This review article provides updated information on recent developments regarding the available antibody or antigen/nucleic acid based biomarkers for longitudinal monitoring of patients with VL or PKDL and emphasizes the need for availability of studies pertaining to quantification of treatment response or relapse.

The diagnostic accuracy of direct agglutination test for serodiagnosis of human visceral leishmaniasis: a systematic review with meta-analysis

BACKGROUND

Direct agglutination test (DAT) as a simple, accurate and reliable method, has been widely used for serodiagnosis of visceral leishmaniasis (VL) during the last three decades. The present study is a systematic review and meta-analysis to evaluate the diagnostic accuracy of DAT for serodiagnosis of human VL.

METHODS

Electronic databases, including MEDLINE (via PubMed), SCOPUS, Web of Science, SID and Mag Iran (two Persian scientific search engines) were searched from December 2004 to April 2019. We determined the pooled sensitivity and specificity rates of DAT for the diagnosis of human VL, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic (ROC) curves parameters across the eligible studies.

RESULTS

Of the 2928 records identified in the mentioned electronic databases and after examining reference lists of articles, 24 articles met inclusion criteria and were enrolled in the systematic review and out of them 20 records qualified for meta-analysis. The pooled sensitivity and specificity rates of DAT was 96% [95% CI, 92-98] and 95% [CI95% 86-99], respectively. The likelihood ratio of a positive test (LR+) was found to be 21 [CI95%, 6.6-66.5] and the likelihood ratio of a negative test (LR-) was found to be 0.04 [(CI95%, 0.02-0.08]. The combined estimate of the diagnostic odds ratio for DAT was high [467 (CI95%, 114-1912]). We found that the summary receiver operating characteristic curve (SROC) is positioned near the upper left corner of the curve and the area under curve (AUC) was 0.98 (95% CI, 0.97 to 0.99).

CONCLUSION

Referring to our analysis, we determined that DAT can be considered as a valuable tool for the serodiagnosis of human VL with high sensitivity and specificity. As DAT is a simple, accurate and efficient serological test, it can be recommended for serodiagnosis of human VL particularly in endemic areas.

Evidence-based diagnostic algorithm for visceral leishmaniasis in Bangladesh

Evidence-based diagnostic algorithm is highly recommended for the visceral leishmaniasis (VL). This cross-sectional study was performed in Bangladesh to evaluate VL diagnostic tools including serology, buffy coat smear microscopy for LD body and various DNA-based techniques using buffy coat in 100 confirmed VL cases and 100 controls. The performance of tools against spleen smear (gold standard) was evaluated using kappa coefficient. Diagnostic precision and other inherent indicators were considered for index scoring (IS) of performance of tools using factor analysis. A diagnostic algorithm was formulated based on the IS and availability of the tools at different health care facilities of Bangladesh. A high level of agreement (kappa ≥  0.80) was observed for all the diagnostic tools. The highest kappa coefficients were found for rK39 RDT and rK39 ELISA (0.95), followed by ssuRNA-PCR (0.94), Buffy coat smear (0.93), rK28 ELISA (0.92), rK28 RDT (0.89), LAMP (0.89), Mini-exon PCR (0.86), ITS1 (0.85), and ITS2 PCR (0.80). rK39 RDT was found to be the best diagnostic test (IS: 1.7) followed by rK28 RDT (IS: 1.5), buffy coat smear microscopy (IS: 0.5), rK39 & rK28 ELISA (IS: 0.3), ssuRNA-PCR (IS: -0.7) and LAMP, Mini-exon, ITS1, & ITS2 PCR (IS: -0.9). rK39 RDT has been proposed as the best option for primary health care facilities, while buffy coat smear microscopy was found to be a good adjunct for confirmation of serology-positive cases and proposed for secondary and tertiary facilities. ssuRNA-PCR or LAMP can be an alternate confirmation tool only applicable to the tertiary facilities.

Cost-effectiveness of serological tests for human visceral leishmaniasis in the Brazilian scenario

Human visceral leishmaniasis (VL) is a severe and potentially fatal parasitic disease if not correctly diagnosed and treated. Brazil is one of the three countries most endemic for VL and, like most countries affected by this disease, has a large budget constraint for the incorporation of new health technologies. Although different diagnostic tests for VL are currently available in the country, economic studies evaluating diagnostic kits are scarce. The objective of this study was to conduct a cost-effectiveness analysis of the nine available diagnostic tests for human VL in HIV-infected and uninfected patients in Brazil. The perspective of analysis was the Brazilian public health system, and the outcome of interest was "cases diagnosed correctly". The costs of the tests were estimated using the microcosting technique, and comparisons were performed with decision trees. Sensitivity analyses were explored applying variations in cost and effectiveness values. For VL diagnosis among HIV-uninfected patients, using blood samples for the rapid tests (RDTs), the noncommercial direct agglutination test (DAT-LPC) and IT-LEISH were cost-effective tests compared with the baseline OnSite test, but they presented different incremental cost-effectiveness ratios (ICER) of US$7.04 and US$ 205.40, respectively. Among HIV-infected patients, DAT-LPC was the most cost-effective diagnostic test. Comparisons among the tests with the same methodology, based on the low ICER values, revealed that IT-LEISH was the most cost-effective test among the RDTs and the Ridascreen Leishmania Ab among the ELISA tests. These results confirm that cost-effectiveness analyses can provide useful information to support the incorporation of new health technologies within a known scenario and willingness to pay threshold. It was observed that tests based on the same methodologies presented different cost-effectiveness ratios for the same group of patients and that different tests should be recommended for different patient groups. DAT-LPC was an important cost-effective strategy for all patients, requiring minimum laboratorial infrastructure, and IT-LEISH was the cost-effective test for VL screening in HIV-uninfected patients. IT-LEISH and DAT-LPC have complementary profiles and should both be provided by the Brazilian health system.

Which Are the Optimal Criteria for the Diagnosis of Allergic Bronchopulmonary Aspergillosis? A Latent Class Analysis

BACKGROUND

The ideal criteria for diagnosing allergic bronchopulmonary aspergillosis (ABPA) remain unknown because of the lack of a criterion standard. Latent class analysis using a probabilistic modeling technique can circumvent the need for a reference standard.

OBJECTIVE

To compare the diagnostic performance of various criteria used for evaluating ABPA.

METHODS

We prospectively enrolled consecutive cases of bronchial asthma and performed a series of investigations used for the diagnosis of ABPA. We used latent class analysis to analyze the performance of various existing and novel diagnostic criteria.

RESULTS

Of the 543 subjects (mean age, 37 years; 319 women), 338 (62.2%) and 205 (37.8%) were labeled as "mild-to-moderate" and "severe" asthma cases, respectively. The subjects with severe asthma had a longer duration of asthma and a higher number of exacerbations in the previous year. The prevalence of Aspergillus fumigatus sensitization was 41% and 30%, using the A fumigatus-specific IgE and skin test, respectively. The prevalence of ABPA was 16%, using both the Rosenberg-Patterson and the International Society for Human and Animal Mycology (ISHAM)-ABPA Working Group criteria. The ISHAM criteria were slightly more sensitive (89% vs 81%) and specific (99% vs 98%) than the Patterson criteria. We obtained optimal diagnostic performance by altering the existing ISHAM criteria (serum total IgE >500 international units/mL, excluding the skin test, and using computed tomography of thorax instead of chest radiograph).

CONCLUSIONS

The ISHAM-ABPA Working Group criteria were only marginally better than the Patterson criteria in diagnosing ABPA among patients with asthma younger than 66 years. The diagnostic performance however improved by modifying the prevailing ISHAM criteria, but with increased cost.

B. Valadas SY, L. Sousa-Gomes M, Lauletta Lindoso JA, Cupolillo E, Ruiz-Postigo JA, Argaw D, Sanchez-Vazquez MJ. Premature deaths by visceral leishmaniasis in Brazil investigated through a cohort study: A challenging opportunity?

BACKGROUND

Visceral Leishmaniasis (VL) is the most severe form of leishmaniasis because it can lead to death. In the Americas, 96% of cases are in Brazil, and despite efforts, the fatality rate has increased in the past years. We analyzed deaths associated to VL in Brazil and investigated the factors that could influence on the timeliness of fatal outcome with emphasis on time (tStoD).

METHODOLOGY

The registered deaths by VL were sourced from the Brazilian National Notification System from 2007-2014. Through a retrospective cohort study, univariate and multivariable Cox proportional hazards model analysis were performed and investigated the factors that could influence the time (tStoD). These factors were analyzed through survival models.

RESULTS

Out of the 1,589 reported deaths, the median for onset of the symptoms and the case notification date (tStoN) is 25 days (10-61), and for date of case notification and death (tNotD) is 9 days (4-17). The time (tStoN) to event investigation for HIV non-infected individuals was 1.4 (1.16-1.68) greater than the HIV positive group. At the same time peri-urban and urban area were 0.83 (0.47-1.44) and 1.33 (1.16-1.52), respectively. The explorations revealed apparent differences between the time to event investigation (both for tStoN and tNotD) and the age at the onset of the symptoms. According to the tStoN the rate of notification is 1.73 times greater in patients under 5 years old at the onset of the clinical symptoms compared to older patients.

CONCLUSION

VL patients under 5 years old were diagnosed earlier and had shorter survival. It could mean that in younger population, although properly diagnosed, the fatality pattern might be related to the severity of the disease. Main host characteristics were evaluated, and age and co-infections seem to have an impact in the disease progression.

Systematic review on antigens for serodiagnosis of visceral leishmaniasis, with a focus on East Africa

Background

Accurate and accessible diagnosis is key for the control of visceral leishmaniasis (VL). Yet, current diagnostic tests for VL have severe limitations: they are invasive or not suitable as point of care (POC) test or their performance is suboptimal in East Africa. We analysed the antigens in the VL serodiagnostics development pipeline to identify shortcomings and to propose strategies in the development of an alternative POC test for VL in East Africa.

Objectives

The objective of this study was to identify and to analyse all antigens for VL serodiagnosis that have been published before 2018 in order to identify candidates and gaps in the pipeline for a new POC test in East Africa.

Methods

A systematic literature search was performed on PubMed for original research articles on Leishmania-specific antigens for antibody detection of VL in humans. From each article, the following information was extracted: the antigen name, test format and characteristics, its reported sensitivity and specificity and study cohort specifications.

Results

One hundred and seven articles containing information about 96 tests based on 89 different antigens were included in this study. Eighty six of these tests, comprising 80 antigens, were evaluated in phase I and II studies only. Only 20 antigens, all of which are native, contain a carbohydrate and/or lipid moiety. Twenty-four antigens, of which 7 are non-native, are composed of antigen mixtures. Nineteen tests, comprising 18 antigens, have been evaluated on East African specimens, of which only 2 (rK28 based immunochromatographic test and intact promastigote based indirect fluorescent antibody technique) consistently showed sensitivities above 94 and specificities above 97% in a phase III study and one in a phase II study (dot blot with SLA). Only rK28 is a non-native mixture of antigens which we consider suitable for further evaluation and implementation.

Conclusions

The development pipeline for an alternative serodiagnostic test for VL is almost empty. Most antigens are not sufficiently evaluated. Non-protein antigens and antigen mixtures are being neglected. We propose to expand the evaluation of existing antigen candidates and to investigate the diagnostic potential of defined non-native carbohydrate and lipid antigens for VL serodiagnosis in East Africa.

Visceral leishmaniasis is a potentially fatal disease that affects more than 20 000 people every year. Its diagnosis is difficult since the clinical symptoms are not specific and the existing diagnostic tests are not useful in limited resource countries or they a not accurate enough in East Africa. In this review we performed a systematic search of the published literature to analyse the potential candidate antigens in the pipeline for a new antibody detection test in East Africa. We found 96 tests based on 89 antigens. Eighty six of these tests were evaluated in a study design that is insufficient (phase I and II) to make conclusions on their performance in clinical practice. We found that the candidate antigens either lacked carbohydrate or lipid structures or are based on single antigens as opposed to mixtures or are extracted from the causative parasite itself, making them expensive and prone to variations. Considering that the most widely used diagnostic test does not detect all cases of visceral leishmaniasis in East Africa, we analysed how many of the candidate antigens were tested on East African specimens: We found that only 2 tests (rK28 based immunochromatographic test and the intact promastigote based indirect fluorescent antibody technique) that were tested in a phase III study and only one (dot blot with SLA) that was tested in a phase II study performed well according to our criteria. Due to the antigen characteristics we consider only the rK28 based test as suitable for further evaluation and implementation.

Cost-effectiveness analysis of diagnostic-therapeutic strategies for visceral leishmaniasis in Brazil

INTRODUCTION

Visceral leishmaniasis (VL) is fatal if not diagnosed and treated. This study aimed to estimate the cost-effectiveness of diagnostic-therapeutic alternatives for VL in Brazil.

METHODS

A decision model estimated the life expectancy and costs of six diagnostic-therapeutic strategies.

RESULTS

IT LEISH + liposomal amphotericin B emerged the best option, presenting lower costs and higher effectiveness. DAT-LPC + liposomal amphotericin B showed an incremental cost-effectiveness ratio of US$ 326.31 per life year.

CONCLUSIONS

These findings indicate the feasibility of incorporating DAT and designating liposomal amphotericin B as the first-line drug for VL in Brazil.

Budgetary impact of diagnostic tests for visceral leishmaniasis in Brazil

The aim of the present study was to estimate the financial costs of the incorporation and/or replacement of diagnostic tests for human visceral leishmaniasis (VL) in Brazil. The analysis was conducted from the perspective of the Brazilian Unified National Health System (SUS) over a period of three years. Six diagnostic tests were evaluated: the indirect immunofluorescence antibody test (IFAT), the IT LEISH rapid test, the parasitological examination of bone marrow aspirate, the direct agglutination test (DAT-LPC) standardized in the Clinical Research Laboratory, René Rachou Institute of the Oswaldo Cruz Foundation, the Kalazar Detect rapid test, and polymerase chain reaction (PCR). The assumptions used were the number of suspected cases of VL reported to the Brazilian Ministry of Health in 2014 and the direct cost of diagnostic tests. The costs to diagnose suspected cases of VL over three years using the IFAT and the DAT-LPC were estimated at USD 280,979.91 and USD 121,371.48, respectively. The analysis indicated that compared with the use of the IFAT, the incorporation of the DAT-LPC into the SUS would result in savings of USD 159,608.43. With regard to the budgetary impact of rapid tests, the use of IT LEISH resulted in savings of USD 21.708,72 over three years. Compared with a parasitological examination, diagnosis using PCR resulted in savings of USD 3,125,068.92 over three years. In this study, the replacement of the IFAT with the DAT-LPC proved financially advantageous. In addition, the replacement of the Kalazar Detect rapid test with the IT LEISH in 2015 was economically valuable, and the replacement of parasitological examination with PCR was indicated.

Cost-effectiveness of diagnostic-therapeutic strategies for paediatric visceral leishmaniasis in Morocco

Introduction

Visceral leishmaniasis (VL) is a neglected parasitic disease with a high fatality rate if left untreated. Endemic in Morocco, as well as in other countries in the Mediterranean basin, VL mainly affects children living in rural areas. In Morocco, the direct observation of Leishmania parasites in bone marrow (BM) aspirates is used to diagnose VL and meglumine antimoniate (SB) is the first line of treatment. Less invasive, more efficacious and safer alternatives exist. In this study we estimate the cost-effectiveness of alternative diagnostic-therapeutic algorithms for paediatric VL in Morocco.

Methods

A decision tree was used to estimate the cost-effectiveness of using BM or rapid diagnostic tests (RDTs) as diagnostic tools and/or SB or two liposomal amphotericin B (L-AmB) regimens: 6-day and 2-day courses to treat VL. Incremental cost-effectiveness ratios, expressed as cost per death averted, were estimated by comparing costs and effectiveness of the alternative algorithms. A threshold analysis evaluated at which price L-AmB became cost-effective compared with current practices.

Results

Implementing RDT and/or L-AmB treatments would be cost-effective in Morocco according to the WHO thresholds. Introducing the 6-day course L-AmB, current second-line treatment, would be highly cost-effective if L-AmB price was below US$100/phial. The 2-day L-AmB treatment, current standard treatment of paediatric VL in France, is highly cost-effective, with L-AmB at its market price (US$165/phial).

Conclusions

The results of this study should encourage the implementation of RDT and/or short-course L-AmB treatments for paediatric VL management in Morocco and other North African countries.

Acceptance and potential barriers to effective use of diagnostic tests for visceral leishmaniasis in an urban area in Brazil

INTRODUCTION

Acceptance of the IT LEISH(r) and direct agglutination test- made in the Laboratório de Pesquisas Clínicas (DAT-LPC) by healthcare professionals and patients suspected of visceral leishmaniasis (VL) in Ribeirão das Neves was evaluated.

METHODS

Ninety-two patients and 47 professionals completed three questionnaires.

RESULTS

Eighty-eight (96%) patients considered fingertip blood collection a positive test feature, and 86% (37) and 91% of professionals considered the IT LEISH(r) easy to perform and interpret, respectively. All professionals classified the DAT-LPC as simple and easy.

CONCLUSIONS

Patients and healthcare professionals in Ribeirão das Neves demonstrated a high degree of acceptance of the IT LEISH(r) and DAT-LPC.

Cost-effectiveness analysis of diagnostic tests for human visceral leishmaniasis in Brazil

BACKGROUND

The objective of study was to estimate the incremental cost-effectiveness ratio (ICER) of diagnostic options for visceral leishmaniasis (VL) in Brazil.

METHODS

Six diagnostic tests were considered: IT LEISH, Kalazar Detect, DAT-LPC (DAT made in the Laboratório de Pesquisas Clínicas), IFAT, PCR and direct examination of bone marrow aspirate performed in either an ambulatory or a hospital setting. A database was built using the cost and effectiveness. The perspective of this study was the Brazilian public healthcare system and the results were expressed in costs per correctly diagnosed cases.

RESULTS

In a favorable hypothetical scenario, DAT-LPC presented the lowest cost (US$4.92) and highest effectiveness (99%). Paired analyses showed that IT LEISH was dominant compared to IFAT, microscopy and Kalazar Detect and that Kalazar Detect was dominant over IFAT and microscopy. PCR was dominant over the bone marrow aspirate in the hospital and showed an ICER of 57.76 compared with aspirate in an ambulatory setting.

CONCLUSIONS

These results highlight the need for the revision of algorithm for VL diagnostic in Brazil. Replacements of IFAT with DAT-LPC, Kalazar Detect with IT LEISH and bone marrow aspirate performed in a hospital setting with PCR are cost-effective public health measures.

Study of implementation and direct cost estimates for diagnostic tests for human visceral leishmaniasis in an urban area in Brazil

This work reports the process and costs of comprehensively implementing two tests to decentralize the diagnosis of visceral leishmaniasis (VL) in an endemic city in Brazil: a rapid test (IT LEISH) and a direct agglutination test (DAT-LPC). The implementation began by training health professionals to perform the tests. Estimation of the training costs considered the proportional remuneration of all professionals involved and the direct costs of the tests used for training. The study was conducted between November 2011 and November 2013. During that time, 17 training sessions were held, and 175 professionals were trained. The training cost for each professional was US$ 7.13 for the IT LEISH and US$ 9.93 for the DAT-LPC. The direct costs of the IT LEISH and DAT-LPC were estimated to be US$ 6.62 and US$ 5.44, respectively. This first evaluation of the implementation of these diagnostic tests indicates the feasibility of decentralizing both methods to extend access to VL diagnosis in Brazil.

The Rapid Test Based on Leishmania infantum Chimeric rK28 Protein Improves the Diagnosis of Canine Visceral Leishmaniasis by Reducing the Detection of False-Positive Dogs

Visceral Leishmaniasis (VL) has spread to many urban centers worldwide. Dogs are considered the main reservoir of VL, because canine cases often precede the occurrence of human cases. Detection and euthanasia of serologically positive dogs is one of the primary VL control measures utilized in some countries, including Brazil. Using accurate diagnostic tests can minimize one undesirable consequence of this measure, culling false-positive dogs, and reduce the maintenance of false-negative dogs in endemic areas. In December 2011, the Brazilian Ministry of Health replaced the ELISA (EIE CVL) screening method and Indirect Immunofluorescence Test (IFI CVL) confirmatory method with a new protocol using the rapid DPP CVL screening test and EIE CVL confirmatory test. A study of diagnostic accuracy of these two protocols was done by comparing their performance using serum samples collected from a random sample of 780 dogs in an endemic area of VL. All samples were evaluated by culture and real time PCR; 766 out of the 780 dogs were tested using the previous protocol (IFI CVL + EIE CVL) and all 780 were tested using the current protocol (DPP CVL + EIE CVL). Performances of both diagnostic protocols were evaluated using a latent class variable as the gold standard. The current protocol had a higher specificity (0.98 vs. 0.95) and PPV (0.83 vs. 0.70) than the previous protocol, although sensitivity of these two protocols was similar (0.73). When tested using sera from asymptomatic animals, the current protocol had a much higher PPV (0.63 vs. 0.40) than the previous protocol (although the sensitivity of either protocol was the same, 0.71). Considering a range of theoretical CVL prevalences, the projected PPVs were higher for the current protocol than for the previous protocol for each theoretical prevalence value. The findings presented herein show that the current protocol performed better than previous protocol primarily by reducing false-positive results.

Comparative diagnostic accuracy of ganglion cell-inner plexiform and retinal nerve fiber layer thickness measures by Cirrus and Spectralis optical coherence tomography in relapsing-remitting multiple sclerosis

Objective. To estimate sensitivity and specificity of several optical coherence tomography (OCT) measurements for detecting retinal thickness changes in patients with relapsing-remitting multiple sclerosis (RRMS), such as macular ganglion cell-inner plexiform layer (GCIPL) thickness measured with Cirrus (OCT) and peripapillary retinal nerve fiber layer (pRNFL) thickness measured with Cirrus and Spectralis OCT. Methods. Seventy patients (140 eyes) with RRMS and seventy matched healthy subjects underwent pRNFL and GCIPL thickness analysis using Cirrus OCT and pRNFL using Spectralis OCT. A prospective, cross-sectional evaluation of sensitivities and specificities was performed using latent class analysis due to the absence of a gold standard. Results. GCIPL measures had higher sensitivity and specificity than temporal pRNFL measures obtained with both OCT devices. Average GCIPL thickness was significantly more sensitive than temporal pRNFL by Cirrus (96.34% versus 58.41%) and minimum GCIPL thickness was significantly more sensitive than temporal pRNFL by Spectralis (96.41% versus 69.69%). Generalised estimating equation analysis revealed that age (P = 0.030), optic neuritis antecedent (P = 0.001), and disease duration (P = 0.002) were significantly associated with abnormal results in average GCIPL thickness. Conclusion. Average and minimum GCIPL measurements had significantly better sensitivity to detect retinal thickness changes in RRMS than temporal pRNFL thickness measured by Cirrus and Spectralis OCT, respectively.

Evaluating the accuracy of molecular diagnostic testing for canine visceral leishmaniasis using latent class analysis

Host tissues affected by Leishmania infantum have differing degrees of parasitism. Previously, the use of different biological tissues to detect L. infantum DNA in dogs has provided variable results. The present study was conducted to evaluate the accuracy of molecular diagnostic testing (qPCR) in dogs from an endemic area for canine visceral leishmaniasis (CVL) by determining which tissue type provided the highest rate of parasite DNA detection. Fifty-one symptomatic dogs were tested for CVL using serological, parasitological and molecular methods. Latent class analysis (LCA) was performed for accuracy evaluation of these methods. qPCR detected parasite DNA in 100% of these animals from at least one of the following tissues: splenic and bone marrow aspirates, lymph node and skin fragments, blood and conjunctival swabs. Using latent variable as gold standard, the qPCR achieved a sensitivity of 95.8% (CI 90.4–100) in splenic aspirate; 79.2% (CI 68–90.3) in lymph nodes; 77.3% (CI 64.5–90.1) in skin; 75% (CI 63.1–86.9) in blood; 50% (CI 30–70) in bone marrow; 37.5% (CI 24.2–50.8) in left-eye; and 29.2% (CI 16.7–41.6) in right-eye conjunctival swabs. The accuracy of qPCR using splenic aspirates was further evaluated in a random larger sample (n = 800), collected from dogs during a prevalence study. The specificity achieved by qPCR was 76.7% (CI 73.7–79.6) for splenic aspirates obtained from the greater sample. The sensitivity accomplished by this technique was 95% (CI 93.5–96.5) that was higher than those obtained for the other diagnostic tests and was similar to that observed in the smaller sampling study. This confirms that the splenic aspirate is the most effective type of tissue for detecting L. infantum infection. Additionally, we demonstrated that LCA could be used to generate a suitable gold standard for comparative CVL testing.

Rapid tests for the diagnosis of visceral leishmaniasis in patients with suspected disease

BACKGROUND

The diagnosis of visceral leishmaniasis (VL) in patients with fever and a large spleen relies on showing Leishmania parasites in tissue samples and on serological tests. Parasitological techniques are invasive, require sophisticated laboratories, consume time, or lack accuracy. Recently, rapid diagnostic tests that are easy to perform have become available.

OBJECTIVES

To determine the diagnostic accuracy of rapid tests for diagnosing VL in patients with suspected disease presenting at health services in endemic areas.

SEARCH METHODS

We searched MEDLINE, EMBASE, LILACS, CIDG SR, CENTRAL, SCI-expanded, Medion, Arif, CCT, and the WHO trials register on 3 December 2013, without applying language or date limits.

SELECTION CRITERIA

This review includes original, phase III, diagnostic accuracy studies of rapid tests in patients clinically suspected to have VL. As reference standards, we accepted: (1) direct smear or culture of spleen aspirate; (2) composite reference standard based on one or more of the following: parasitology, serology, or response to treatment; and (3) latent class analysis.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed quality of included studies using the QUADAS-2 tool. Discrepancies were resolved by a third author. We carried out a meta-analysis to estimate sensitivity and specificity of rapid tests, using a bivariate normal model with a complementary log-log link function. We analysed each index test separately. As possible sources of heterogeneity, we explored: geographical area, commercial brand of index test, type of reference standard, disease prevalence, study size, and risk of bias (QUADAS-2). We also undertook a sensitivity analysis to assess the influence of imperfect reference standards.

MAIN RESULTS

Twenty-four studies containing information about five index tests (rK39 immunochromatographic test (ICT), KAtex latex agglutination test in urine, FAST agglutination test, rK26 ICT, and rKE16 ICT) recruiting 4271 participants (2605 with VL) were included. We carried out a meta-analysis for the rK39 ICT (including 18 studies; 3622 participants) and the latex agglutination test (six studies; 1374 participants). The results showed considerable heterogeneity. For the rK39 ICT, the overall sensitivity was 91.9% (95% confidence interval (95% CI) 84.8 to 96.5) and the specificity 92.4% (95% CI 85.6 to 96.8). The sensitivity was lower in East Africa (85.3%; 95% CI 74.5 to 93.2) than in the Indian subcontinent (97.0%; 95% CI 90.0 to 99.5). For the latex agglutination test, overall sensitivity was 63.6% (95% CI 40.9 to 85.6) and specificity 92.9% (95% CI 76.7 to 99.2).

AUTHORS' CONCLUSIONS

The rK39 ICT shows high sensitivity and specificity for the diagnosis of visceral leishmaniasis in patients with febrile splenomegaly and no previous history of the disease, but the sensitivity is notably lower in east Africa than in the Indian subcontinent. Other rapid tests lack accuracy, validation, or both.

Diagnostic performance of various tests and criteria employed in allergic bronchopulmonary aspergillosis: a latent class analysis

Aim

The efficiency of various investigations and diagnostic criteria used in diagnosis of allergic bronchopulmonary aspergillosis (ABPA) remain unknown, primarily because of the lack of a gold standard. Latent class analysis (LCA) can provide estimates of sensitivity and specificity in absence of gold standard. Herein, we report the performance of various investigations and criteria employed in diagnosis of ABPA.

Methods

Consecutive subjects with asthma underwent all the following investigations Aspergillus skin test, IgE levels (total and A.fumigatus specific), Aspergillus precipitins, eosinophil count, chest radiograph, and high-resolution computed tomography (HRCT) of the chest. We used LCA to estimate the performance of various diagnostic tests and criteria in identification of ABPA.

Results

There were 372 asthmatics with a mean age of 35.9 years. The prevalence of Aspergillus sensitization was 53.2%. The sensitivity and specificity of various tests were Aspergillus skin test positivity (94.7%, 79.7%); IgE levels>1000 IU/mL (97.1%, 37.7%); A.fumigatus specific IgE levels>0.35 kUA/L (100%, 69.3%); Aspergillus precipitins (42.7%, 97.1%); eosinophil count>1000 cells/µL (29.5%, 93.1%); chest radiographic opacities (36.1%, 92.5%); bronchiectasis (91.9%, 80.9%); and, high-attenuation mucus (39.7%, 100%). The most accurate criteria was the Patterson criteria using six components followed by the Agarwal criteria. However, there was substantial decline in accuracy of the Patterson criteria if components of the criteria were either increased or decreased from six.

Conclusions

A.fumigatus specific IgE levels and high-attenuation mucus were found to be the most sensitive and specific test respectively in diagnosis of ABPA. The Patterson criteria remain the best diagnostic criteria however they have good veridicality only if six criteria are used.