Accuracy of diagnostic tests for American tegumentary leishmaniasis: a systematic literature review with meta-analyses

Evaluation of the public health laboratory network for tegumentary leishmaniasis in an endemic area of Brazil

Diagnostic networks ensure efficiency in disease diagnosis. A descriptive study evaluated the network of public health laboratories (NPHL) in Minas Gerais State, Brazil, using diagnostic results for tegumentary leishmaniasis (TL) from the laboratory management system in 2017-2020. Out of 1,369 individuals analyzed, 704 (51.4%) cases of TL were confirmed, with 610 (86.7%) by direct parasitological examination (DPE) and 94 (13.4%) by polymerase chain reaction (PCR). Notably, 25.3% of cases with DPE-negative results were PCR-positive. Consecutive diagnostic tests enhanced diagnosis of TL. NPHL-MG is a promising model for expanding similar networks and improving disease control.

Diagnostic performance of Leishmania braziliensis and Leishmania peruviana antigens in the immunoblot method for the detection of american tegumentary leishmaniasis

BACKGROUND

Motivation for the study. To contribute to the immunogenic character of soluble and excretion/secretion antigens of Leishmania braziliensis and Leishmania peruviana with the aim of identifying proteins with diagnostic potential.

BACKGROUND

Main findings. The soluble antigen of Leishmania braziliensis has a sensitivity in the detection of ATL of 87.7%, specificity of 100% and a false positive rate of 20% against sera from patients with Chagas disease and 8.3% with mycosis.

BACKGROUND

Implications. Immunoblot can improve the resolution capacity in the serological diagnosis of American tegumentary Leishmaniasis, particularly in patients where the length of the disease and the clinical form make difficult the diagnosis by parasitological methods.

BACKGROUND

This study aimed to determine the performance of Leishmania braziliensis and Leishmania peruviana antigens in the detection of ATL by using serum samples obtained between 2013 - 2016. The obtained soluble and excretion/secretion antigens were transferred to membrane nitrocellulose by immunoblot assay. The evaluation was carried out against sera confirmed for ATL, at a confidence level of 95%, determining that the soluble antigen of Leishmania braziliensis had a sensitivity of 87.7%, specificity of 100% and area under the curve of 0.95; on the other hand, Leishmania peruviana showed values of 92.3%, 95.7% and 0.94, respectively. According to the results, we recommend that the reported immunogenic regions should be characterized and analyzed in order to continue with the development of recombinant and synthetic proteins, aimed at improving the efficiency of the serological diagnosis of the disease.

Antigenic reactivity of Leishmania (Viannia) lainsoni axenic amastigote proved to be a suitable alternative for optimizing Montenegro skin test

BACKGROUND

Laboratory diagnosis of American cutaneous leishmaniasis (ACL) requires a tool amenable to the epidemiological status of ACL in Brazil. Montenegro skin test (MST), an efficient immunological tool used for laboratory diagnosis of ACL, induces delayed-type hypersensitivity (DTH) response to the promastigote antigens of Leishmania; however, human immune responses against infection are modulated by the amastigote of the parasite. Leishmania (V.) lainsoni induces strong cellular immunity in humans; therefore, the antigenic reactivity of its axenic amastigote (AMA antigen) to MST was evaluated for the laboratory diagnosis of ACL.

METHODS

Among 70 individuals examined, 60 had a laboratory-confirmed diagnosis of ACL; 53 had localized cutaneous leishmaniasis (LCL), and 7 had mucosal leishmaniasis (ML). Patients were treated at the Evandro Chagas Institute's leishmaniasis clinic, Pará State, Brazil. Ten healthy individuals with no history of ACL (control group) were also examined. Leishmania (V.) braziliensis promastigote antigen (PRO) was used to compare the reactivity with that of AMA antigen. Paired Student's t-test, kappa agreement, and Spearman test were used to evaluate the reactivity of AMA and PRO.

RESULTS

The mean reactivity of AMA in ACL patients was 19.4 mm ± 13.3, which was higher (P < 0.001) than that of PRO: 12.1 mm ± 8.1. MST reactivity according to the clinical forms revealed that AMA reactivity in LCL and ML, 18.8 mm ± 13.3 and 24.3 mm ± 13.7, was higher (P < 0.001) than that of PRO, 11.8 mm ± 8.2 and 14.6 mm ± 8.4, respectively.

CONCLUSION

AMA reactivity was higher than that of PRO, indicating that AMA is a promising alternative for optimizing MST in the laboratory diagnosis of ACL.

Development and accuracy evaluation of a new loop-mediated isothermal amplification assay targeting the HSP70 gene for the diagnosis of cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a global public health problem caused by species on the genus Leishmania and is the most prevalent clinical form of leishmaniasis. The aim of this study was to develop a new LAMP assay for Leishmania sp. based on HSP70 gene and evaluate it clinically for molecular diagnosis of CL. The study was carried out in the following stages: i) design of primers based on HSP70 gene of Leishmania sp.; ii) evaluation of detection limit and analytical specificity; iii) estimation of the accuracy of LAMP-Leish/HSP70 assay for diagnosing CL. A total of 100 skin biopsy samples from patients, comprising 60 CL cases and 40 non-cases, were analyzed in this study. One LAMP assay using HSP70 gene as molecular target were standardized, and the observed detection limit was 100fg of L. braziliensis purified DNA. The LAMP-Leish/HSP70 assay was specific for Leishmania spp. The LAMP-Leish/HSP70 assay showed an accuracy of 92%, and positivity rates were not affected by lesion onset time or parasite load. This novel LAMP assay targeting the HSP70 gene of Leishmania sp. has the potential to be a useful tool to integrate into routine diagnosis for suspected cases of CL.

Tegumentary leishmaniasis in Brazil: priority municipalities and spatiotemporal relative risks from 2001 to 2020

Understanding the distribution of tegumentary leishmaniasis (TL) in different periods enables the adequate conduction of actions at the public health level. The present study analyzes the spatiotemporal evolution of TL incidence rates in the municipalities of Brazil and identifies priority areas from 2001 to 2020. Notifications of new cases were analyzed employing space-time scan statistics and Local Indicators of Spatial Association. As TL incidence rates presented a downward trend in most Brazilian municipalities, spatiotemporal clusters of high relative risks (RR) were more frequent in the first decade of the series. There was a concentration of those clusters in the North and Northeast regions, mainly in the Legal Amazon area. More recent high-RR areas were identified in municipalities of different regions. The number of priority municipalities showed a stable trend in Brazil. There was a great concentration of such municipalities in the states of Acre, Mato Grosso, Rondônia, Pará, and Amapá, as well as large areas in Roraima, Amazonas, Maranhão, and Tocantins, and smaller areas in the states of Goiás, Ceará, Bahia, Minas Gerais, São Paulo, and Paraná. The present study contributes to the understanding of the historical evolution of TL in Brazil and subsidizes actions to combat the disease.

The need for culture in tegumentary leishmaniasis diagnosis in Bolivia: A comparative evaluation of four parasitological techniques using two sampling methods

Leishmaniases are zoonotic diseases caused by protozoa of the genus Leishmania. In Bolivia, leishmaniasis occurs mainly in the cutaneous form (CL) followed by the mucosal or mucocutaneous form (ML or MCL), grouped as tegumentary leishmaniosis (TL), while cases of visceral leishmaniasis (VL) are rare. The cases of TL are routinely diagnosed by parasitological methods: Direct Parasitological Exam (DPE) and axenic culture, the latter being performed only by specialized laboratories. The aim of the present study was to optimize the parasitological diagnosis of TL in Bolivia, using two sampling methods. Samples from 117 patients with suspected TL, obtained by aspiration (n = 121) and scraping (n = 121) of the edge of the lesion were tested by: direct parasitological exam, culture in TSTB medium, and miniculture and microculture in Schneider's medium. A positive laboratory result by any of the four techniques evaluated using either of the two sampling methods was considered the gold standard. Of the 117 suspected patients included, TL was confirmed in 96 (82 %), corresponding 79 of the confirmed cases (82.3 %) to CL and 16 (16.7 %) to ML. Parasitological techniques specificity was 100 % and their analytical sensitivity was greater with scraping samples in TSTB culture (98 %). Scraping samples in TSTB and miniculture correlated well with the reference (Cohen's kappa coefficient=0.88) and showed good reliability (Cronbach's alpha coefficient ≥0.91). Microculture provided positive results earlier than the other culture methods (mean day 4.5). By day 14, 98 % of positive cultures had been detected. Scraping sampling and miniculture were associated with higher culture contamination (6 % and 17 %, respectively). Bacterial contamination predominated, regardless of the sampling and culture method, while filamentous fungi and mixed contamination were more frequently observed in cultures from scraping samples. In conclusion: (i) scraping samples proved more suitable for the diagnosis of TL as they increased analytical sensitivity, are less traumatic for the patient and are safer for laboratory personnel than aspirates; (ii) culture, mainly in TSBT medium, should be used for the diagnosis of TL due to its high sensitivity (doubling the number of cases diagnosed by DPE) and its low cost compared to other culture media.

Diagnostic accuracy of qPCR and microscopy for cutaneous leishmaniasis in rural Ecuador: A Bayesian latent class analysis

BACKGROUND

Clinical and laboratory diagnosis of cutaneous leishmaniasis (CL) is hampered by under-ascertainment of direct microscopy.

METHODS

This study compared the diagnostic accuracy of qPCR on DNA extracted from filter paper to the accuracy of direct smear slide microscopy in participants presenting with a cutaneous lesion suspected of leishmaniasis to 16 rural healthcare centers in the Ecuadorian Amazon and Pacific regions, from January 2019 to June 2021. We used Bayesian latent class analysis to estimate test sensitivity, specificity, likelihood ratios (LR), and predictive values (PV) with their 95% credible intervals (95%CrI). The impact of sociodemographic and clinical characteristics on predictive values was assessed as a secondary objective.

RESULTS

Of 320 initially included participants, paired valid test results were available and included in the diagnostic accuracy analysis for 129 from the Amazon and 185 from the Pacific region. We estimated sensitivity of 68% (95%CrI 49% to 82%) and 73% (95%CrI 73% to 83%) for qPCR, and 51% (95%CrI 36% to 66%) and 76% (95%CrI 65% to 86%) for microscopy in the Amazon and Pacific region, respectively. In the Amazon, with an estimated disease prevalence among participants of 73%, negative PV for qPCR was 54% (95%CrI 5% to 77%) and 44% (95%CrI 4% to 65%) for microscopy. In the Pacific, (prevalence 88%) the negative PV was 34% (95%CrI 3% to 58%) and 37% (95%CrI 3% to 63%). The addition of qPCR parallel to microscopy in the Amazon increases the observed prevalence from 38% to 64% (+26 (95%CrI 19 to 34) percentage points).

CONCLUSION

The accuracy of either qPCR on DNA extracted from filter paper or microscopy for CL diagnosis as a stand-alone test seems to be unsatisfactory and region-dependent. We recommend further studies to confirm the clinically relevant increment found in the diagnostic yield due to the addition of qPCR.

Description of the dermatoscopic features observed in sporotrichosis and American cutaneous leishmaniasis in a reference center in Rio de Janeiro, Brazil

BACKGROUND

The evaluation of American cutaneous leishmaniasis (CL) and sporotrichosis (SP) with dermoscopy may improve the diagnosis accuracy and clinical monitoring.

OBJECTIVES

To describe the dermoscopic findings and patterns of skin lesions of patients with CL and SP followed up at the Laboratory of Clinical Research and Surveillance in Leishmaniasis (LaPClinVigiLeish), Evandro Chagas National Institute of Infectious Diseases (INI), Oswaldo Cruz Foundation, Rio de Janeiro, Brazil.

METHODS

The authors included patients with a diagnosis of CL or SP, who attended at INI/ Fiocruz, between 2019‒2021. All patients had 3 dermoscopic examinations (DermLite DL4): before treatment (T0), during treatment (T1), and after healing (T2). Up to three lesions per patient were evaluated.

RESULTS

The authors studied 47 patients with CL (74 lesions), and 19 patients with SP (24 lesions). The authors described dermoscopic structures such as rosettes, white lines, white dots, brown focal structureless areas, brown lines and dots, white perilesional circles, perilesional hyperchromic circles, microulcerations and the rainbow patterns. The authors created specific patterns; in CL: CL-T0 "central yellow scales with a white perilesional circle pattern", CL-T1 "diffuse structureless white area pattern" and CL-T2 "white and brown focal structureless areas pattern". In SP: SP-T0 the "pustule with erythema pattern"; SP-T1 the "focal structureless white areas with erythema pattern" and SP-T2 the "white linear pattern".

STUDY LIMITATIONS

This study does not correlate dermoscopic findings with time of disease evolution at the first medical examination.

CONCLUSIONS

The recognition of CL and SP dermoscopy patterns may be helpful tool for the differential diagnosis and monitoring of disease evolution.

Temporal patterns, spatial risks, and characteristics of tegumentary leishmaniasis in Brazil in the first twenty years of the 21st Century

BACKGROUND

Tegumentary leishmaniasis (TL) is a significant public health issue in Brazil. The present ecological study describes the clinical and epidemiological characteristics of TL cases reported in the country, and analyzes the spatial and temporal patterns of the incidences and risks of occurrence across the five geopolitical regions and 27 federative units.

METHODOLOGY/PRINCIPAL FINDINGS

Data regarding new cases of TL notified between 2001 and 2020 were obtained from the Information System for Notifiable Diseases of the Brazilian Ministry of Health. Joinpoint and spatial and temporal generalized additive models were used to establish trends in the evolution of TL during the target period. The incidence rate for the entire period was 226.41 cases/100,000 inhabitants. All regions of Brazil showed trends of decreasing incidence rates, albeit with fluctuations at specific times, with the exception of the Southeast where rates have increased since 2014, most particularly in Minas Gerais state. The disease was concentrated predominantly in the North region, with Acre state leading the incidence rank in the whole country, followed by Mato Grosso (Midwest), Maranhão and Bahia (Northeast) states. The spatial distribution of the risk of TL occurrence in relation to the annual averages was relatively stable throughout the period. The cutaneous form of TL was predominant and cases most frequently occurred in rural areas and among men of working age. The ages of individuals contracting TL tended to increase during the time series. Finally, the proportion of confirmations by laboratory tests was lower in the Northeast.

CONCLUSION/SIGNIFICANCE

TL shows a declining trend in Brazil, but its widespread occurrence and the presence of areas with increasing incidence rates demonstrate the persistent relevance of this disease and the need for constant monitoring. Our findings reinforce the importance of temporal and spatial tools in epidemiologic surveillance routines and are valuable for targeting preventive and control actions.

New immunodiagnostic methods for human tegumentary leishmaniasis in the last 10 years: Technological Prospecting

Leishmaniasis is a neglected disease and more than 1 billion people live in endemic areas with the risk of infection worldwide. Although it is an important epidemiological issue, the gold standard method of diagnosis requires invasive sample collection and is accompanied by a high level of sensitivity variation in results. The present study aims to conduct a patent prospection of immunodiagnostic methods for human tegumentary leishmaniasis in the last 10 years, focused on those with high sensitivity and specificity, and simple usability. We searched seven patent databases: The LENS, WIPO, EPO, USPTO, Patent Inspiration, Google patents, and INPI. Eleven patents were found that satisfy our search criteria, with six of them being registered in 2017. Most patents were registered in Brazil. The information obtained here covers the main characteristics of the immunodiagnostic methods evaluated. Moreover, our prospective study reveals the latest biotechnological advancements achieved in the immunodiagnosis of tegumentary leishmaniasis, especially in Brazil, which holds the majority of patents in this subject. However, no patent for immunodiagnostic methods was found in the last three years, which raises concerns about the present and future trends of leishmaniasis diagnosis.

Comparison between Colorimetric In Situ Hybridization, Histopathology, and Immunohistochemistry for the Diagnosis of New World Cutaneous Leishmaniasis in Human Skin Samples

New world cutaneous leishmaniasis (NWCL) is an anthropozoonosis caused by different species of the protozoan Leishmania. Colorimetric in situ hybridization (CISH) was shown to satisfactorily detect amastigote forms of Leishmania spp. in animal tissues, yet it was not tested for the diagnosis of human NWCL. The aim of this study was to compare CISH, histopathology (HP), and immunohistochemistry (IHC) techniques to diagnose NWCL in human cutaneous lesions. The sample comprised fifty formalin-fixed, paraffin-embedded skin biopsy specimens from patients with NWCL caused by L. (V.) braziliensis. These specimens were analyzed by CISH, using a generic probe for Leishmania, IHC, and HP to assess the sensitivity of these methods by using a parasitological culture as a standard reference. Additional specimens from three patients diagnosed with cutaneous mycoses were also included to evaluate cross-reactions between CISH and IHC. The sensitivities of IHC, CISH, and HP for detecting amastigotes was 66%, 54%, and 50%, respectively. IHC, unlike CISH, cross-reacted with different species of fungi. Together, these results demonstrate that CISH may be a complementary assay for the detection of amastigote in the laboratorial diagnosis routine of human NWCL caused by L. (V.) braziliensis.

Study on the zoonotic cycle of tegumentary leishmaniasis in an endemic area of a metropolitan region in the Northeastern region of Brazil

This study was conducted to characterize the transmission cycle of the tegumentary leishmaniasis (TL) in an old colonization area at Pernambuco State, Brazil. The aims were to identify autochthonous cases, sandflies fauna, domestic animals as possible reservoir hosts and the Leishmania species involved in this endemic area. A total of 168 suspected human cases of TL and 272 domestic animals (canine, feline, equine, goat, and sheep) were included. The sandflies were captured and identified by species. Patients were predominantly male and the average age was 37+18.1 years old. Of 85 patients who had skin lesions, 25.6% of them had direct positive smears for TL and 34 isolates were identified as Leishmania (Viannia) braziliensis. The confirmation for TL diagnosed by molecular detection (PCR) was almost three times more sensitive than the direct test [p < 0.001; PR = 2.72] associated with clinical examination. The Kappa test on PCR between two different specimens, biopsy, and skin lesion swab was 60.8% (p < 0.001). More than 200 specimens of sandflies (80 males and 159 females) were captured and identified as Lutzomyia whitmani (99.6%) and Lu. evandroi (0.4%). The detection of L. (V.) braziliensis by Real-Time PCR in the blood of a captured fed female was positive in 59.3% of Lu. whitmani. Of the 272 domestic animals included, 61.76% were male (n = 168). Thirty-six animals (13.2%) had lesions compatible with TL (34 dogs, 1 cat and 1 sheep) and 3 of them, all dogs, had lesions on the snout, showing destruction of cartilage and mucosa. The study suggests the participation of domestic animals as possible reservoirs. However, further studies are necessary to better understand the transmission cycle and take recommended measures in order to control the disease.

Changes in the microbiological diagnosis and epidemiology of cutaneous leishmaniasis in real-time PCR era: A six-year experience in a referral center in Barcelona

BACKGROUND

Leishmaniasis is a neglected disease caused by different species of the protozoa Leishmania spp. Cutaneous lesions are the most common clinical manifestation. This disease is prevalent in tropical and subtropical areas, including the Mediterranean basin. In Spain, Leishmania (L.) infantum is the only endemic species, but imported cases are often diagnosed. Different classical parasitological methods can be performed for cutaneous leishmaniasis (CL) diagnosis; but currently molecular techniques serve as a relevant tool for the detection and characterization of Leishmania parasites. We aimed to evaluate clinical and epidemiological characteristics of CL diagnosed patients by real-time PCR in a tertiary hospital over a six-year period.

METHODOLOGY/PRINCIPAL FINDINGS

Clinical, epidemiological and microbiological data were retrospectively collected and analyzed. In our study, CL was confirmed in 59 (31.4%) out of 188 patients by real-time PCR, showing an increase over recent years: 11 cases of CL between 2014 and 2016 and 48 between 2017 and 2019. Real-time PCR was performed on skin swabs and/or biopsies samples, with a positivity of 38.5% and 26.5%, respectively. Results were 100% concordant when biopsy and skin swab were performed simultaneously. L. (L.) infantum was the most frequent species detected (50%), followed by L. (L.) major (45%) and Viannia subgenus (5%), which were detected only in imported cases. L. (L.) major was almost entirely detected in travelers/migrants from Morocco. Multiple and atypical skin lesions were more common in imported cases than in autochthonous cases (44.4% vs. 21.8%).

CONCLUSIONS/SIGNIFICANCE

An increase in both autochthonous and imported CL cases has been observed in past years in our hospital. Molecular techniques assist in improving CL diagnosis and characterization of the Leishmania species, mainly in imported cases.

Potential antigenic targets used in immunological tests for diagnosis of tegumentary leishmaniasis: A systematic review

Immunological tests may represent valuable tools for the diagnosis of human tegumentary leishmaniasis (TL) due to their simple execution, less invasive nature and potential use as a point-of-care test. Indeed, several antigenic targets have been used with the aim of improving the restricted scenario for TL-diagnosis. We performed a worldwide systematic review to identify antigenic targets that have been evaluated for the main clinical forms of TL, such as cutaneous (CL) and mucosal (ML) leishmaniasis. Included were original studies evaluating the sensitivity and specificity of immunological tests for human-TL, CL and/or ML diagnosis using purified or recombinant proteins, synthetic peptides or polyclonal or monoclonal antibodies to detect Leishmania-specific antibodies or antigens. The review methodology followed PRISMA guidelines and all selected studies were evaluated in accordance with QUADAS-2. Thirty-eight original studies from four databases fulfilled the selection criteria. A total of 79 antigens were evaluated for the detection of antibodies as a diagnostic for TL, CL and/or ML by ELISA. Furthermore, three antibodies were evaluated for the detection of antigen by immunochromatographic test (ICT) and immunohistochemistry (IHC) for CL-diagnosis. Several antigenic targets showed 100% of sensitivity and specificity, suggesting potential use for TL-diagnosis in its different clinical manifestations. However, a high number of proof-of-concept studies reinforce the need for further analysis aimed at verifying true diagnostic accuracy in clinical practice.

Diagnostic performance of a Recombinant Polymerase Amplification Test-Lateral Flow (RPA-LF) for cutaneous leishmaniasis in an endemic setting of Colombia

Background

Control of cutaneous leishmaniasis by public health systems in the Americas relies on case identification and treatment. Point-of-care diagnostics that can be performed by health workers within or near affected communities could effectively bring the health system to the resource-limited sites providing early diagnosis and treatment, reducing morbidity and the burden of disease.

Methodology/principal findings

A cross-sectional study was undertaken to evaluate the diagnostic test performance of Isothermal Recombinase Polymerase Amplification (RPA) targeting Leishmania kinetoplast DNA, coupled with a lateral flow (LF) immunochromatographic strip, in a field setting and a laboratory reference center. Minimally invasive swab and FTA filter paper samples were obtained by community health workers and highly trained technicians from ulcerated lesions of > 2 weeks’ evolution from 118 patients’ ≥ 2 years of age in the municipality of Tumaco, Nariño. Extracted DNA was processed by RPA-LF at a reference center or in a primary health facility in the field. Evaluation was based on a composite “gold standard” that included microscopy, culture, biopsy and real-time polymerase chain reaction detection of Leishmania 18S rDNA. Standard of care routine diagnostic tests were explored as comparators.

Sensitivity and specificity of RPA-LF in the reference lab scenario were 87% (95%CI 74–94) and 86% (95%CI 74–97), respectively. In the field scenario, the sensitivity was 75% (95%CI 65–84) and specificity 89% (95%CI 78–99). Positive likelihood ratios in both scenarios were higher than 6 while negative likelihood ratios ranged to 0.2–0.3 supporting the usefulness of RPA-LF to rule-in and potentially to rule-out infection.

Conclusions/significance

The low complexity requirements of RPA-LF combined with non-invasive sampling support the feasibility of its utilization by community health workers with the goal of strengthening the diagnostic capacity for cutaneous leishmaniasis in Colombia.

Trial registration

ClinicalTrials.gov NCT04500873.

Limited access to diagnosis is a critical determinant of the “neglect” that defines the so-called Neglected Tropical Diseases (NTDs) including cutaneous leishmaniasis. Diagnostic tests that can be performed close to and involve the participation of the affected communities would improve access to treatment as well as diagnosis. Using non-invasive swab and filter paper samples obtained by Community Health Workers, we evaluated the diagnostic performance of an innovative and technically simple molecular test: Isothermal Recombinase Polymerase Amplification (RPA) to detect Leishmania DNA, coupled with a lateral flow (LF) strip to read the results with the naked eye. The RPA-LF test demonstrated high sensitivity and specificity and capacity to rule in or rule out a diagnosis of cutaneous leishmaniasis in both an endemic field setting and reference laboratory. The findings encourage the further optimization of the test format for Point-of-Care diagnosis by health personnel and rural health workers in endemic settings.