Performance of immunological assays for universal and differential diagnosis of HTLV-1/2 infection in candidates for blood donations from the Brazilian Amazon.

The present study compares the ability of distinct immunological assays (chemiluminescence immunoassay-CLIA, western blot-WB and flow cytometry-FC-Simplex and Duplex) to detect anti-HTLV (human T-lymphotropic virus) antibodies in candidates for blood donations at the Amazonas State Blood Center (Brazil) between January 2018 and December 2022. Overall, 257,942 samples from candidates for blood donations were screened using CLIA, which led to 0.15% seropositivity for HTLV (409 samples). A total of 151 candidates for blood donations were enrolled for retesting with CLIA followed by additional testing using WB and FC-Simplex and Duplex analysis. Our results demonstrated that 62% (93/151), 20% (30/151) and 17% (26/151) of the samples presented positive results with retesting using CLIA, WB and FC-Simplex analysis, respectively. Additional analysis of the CLIA, WB and FC-Simplex results revealed an overall agreement of 56% for CLIA and WB (22 co-negative; 30 co-positive samples), 48% for CLIA and FC-Simplex (21 co-negative; 24 co-positive samples) and 80% for WB and FC-Simplex (51 co-negative; 23 co-positive samples). Considering the WB as the reference standard for the diagnosis of infection with HTLV-1/2, we observed that the CLIA results of ≤3.0 RLU and >10.0 RLU in the retest can be used define a negative or positive result, respectively, and could be used as new specific cut-off values. The overall agreement between WB and FC-Duplex for accomplishing the differential diagnosis was evaluated and demonstrated 100% correspondence for the diagnosis of HTLV-1 (15/15) and HTLV-2 (7/7). Our findings demonstrate that gaps in the diagnosis of infection with HTLV-1/2 could be overcome by the simultaneous use of distinct immunological assays during retesting of candidates for blood donations.

IL-10 predicts incident neuroinflammatory disease and proviral load dynamics in a large Brazilian cohort of people living with human T-lymphotropic virus type 1.

Human T-Lymphotropic Virus type-1 (HTLV-1) is a unique retrovirus associated with both leukemogenesis and a specific neuroinflammatory condition known as HTLV-1-Associated Myelopathy (HAM). Currently, most proposed HAM biomarkers require invasive CSF sampling, which is not suitable for large cohorts or repeated prospective screening. To identify non-invasive biomarkers for incident HAM in a large Brazilian cohort of PLwHTLV-1 (n=615 with 6,673 person-years of clinical follow-up), we selected all plasma samples available at the time of entry in the cohort (between 1997-2019), in which up to 43 cytokines/chemokines and immune mediators were measured. Thus, we selected 110 People Living with HTLV-1 (PLwHTLV-1), of which 68 were neurologically asymptomatic (AS) at baseline and 42 HAM patients. Nine incident HAM cases were identified among 68 AS during follow-up. Using multivariate logistic regression, we found that lower IL-10, IL-4 and female sex were independent predictors of clinical progression to definite HAM (AUROC 0.91), and outperformed previously suggested biomarkers age, sex and proviral load (AUROC 0.77). Moreover, baseline IL-10 significantly predicted proviral load dynamics at follow-up in all PLwHTLV-1. In an exploratory analysis, we identified additional plasma biomarkers which were able to discriminate iHAM from either AS (IL6Rα, IL-27) or HAM (IL-29/IFN-λ1, Osteopontin, and TNFR2). In conclusion, female sex and low anti-inflammatory IL-10 and IL-4 are independent risk factors for incident HAM in PLwHTLV-1,while proviral load is not, in agreement with IL-10 being upstream of proviral load dynamics. Additional candidate biomarkers IL-29/IL-6R/TNFR2 represent plausible therapeutic targets for future clinical trials in HAM patients.

Infective dermatitis associated with human T-cell lymphotropic virus type-1, an underdiagnosed disease.

Infective dermatitis associated with human T-cell lymphotropic virus type-1 (HTLV-1) (IDH) is a severe form of chronically infected eczema occurring in early childhood, although very rarely cases have been reported in adults. Most of the cases are from Jamaica and Brazil and occur in individuals with low socioeconomic status. IDH is always associated with refractory Staphylococcus aureus or beta-hemolytic Streptococcus infection of the skin and nasal vestibules. Patients with IDH may develop other even more severe HTLV-1-associated diseases, such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) of early or late appearance and adult T-cell leukemia/lymphoma. In the context of the Brazilian experience, it has been observed that 54% of IDH patients exhibit the juvenile form of HAM/TSP while the estimated incidence of adult HAM/TSP is 3%. As there are no curative treatments for HTLV-1 infection (or vaccines) or most of its associated diseases, prevention of infection is fundamental, mainly by vertical transmission, as it is responsible for the development of IDH, infantojuvenile HAM/TSP, and ATL. Public measures to reduce this transmission must be implemented urgently. Furthermore, it is recommended, mainly in HTLV-1 endemic areas, to search for HTLV-1 infection in all patients with infected eczema, even in adults.

Impact and economic analysis of human T-cell lymphotropic virus type 1 (HTLV-1)-targeted antenatal screening, England and Wales, 2021.

BackgroundHuman T-cell lymphotropic virus type 1 (HTLV-1) is a neglected virus that can cause severe disease and be transmitted from mother to child through breastfeeding. Avoidance of breastfeeding prevents 80% of vertical transmission. The United Kingdom (UK) is currently assessing whether HTLV-1-targeted antenatal screening should be implemented.AimWe aimed to assess the impact and cost-effectiveness of a targeted programme to prevent HTLV-1 vertical transmission in England and Wales.MethodsWe estimated the number of pregnant women who have high risk of HTLV-1 infection based on their or their partner's country of birth. With data from 2021, we used a mathematical model to assess cost-effectiveness of HTLV-1 antenatal screening. We also estimated the annual number of infant infections and the number that could be prevented with screening and intervention.ResultsWe estimate that ca 99,000 pregnant women in England and Wales have high risk of HTLV-1 infection. In the absence of screening, 74 (range: 25-211) HTLV-1 infections in infants would be expected to occur every year in England and Wales. Implementation of targeted screening would prevent 58 (range: 19-164) infant infections annually. The intervention is effective (incremental 0.00333 quality-adjusted life years (QALY)) and cost-saving (GBP -57.56 (EUR -66.85)).ConclusionOur findings support implementation of HTLV-1 targeted antenatal screening to reduce vertical transmission from mothers to infants in the UK.

Inflammatory progressive multifocal leukoencephalopathy with human T-cell lymphotropic virus-1 coinfection.

A middle-aged man with progressive multifocal leukoencephalopathy (PML) in a human T-cell lymphotropic virus type-1 (HTLV-1) carrier on haemodialysis presented with mild dysarthria and ataxia. Brain MRI revealed asymmetric T2-hyperintense lesions in the cerebral white matter, cerebellum and brainstem. A small amount of JC virus (JCV) genome in cerebrospinal fluid was detected by PCR and cerebellar biopsy demonstrated JCV-DNA presence. Pathological findings showed demyelinating lesions and glial cells with mildly enlarged nuclei, accompanied by T-lymphocytes, neutrophils and plasma cell infiltration. The CD4+/CD8+ratio was 0.83. High-dose corticosteroid therapy was effective for inflammatory PML lesions, and the administration of mefloquine combined with mirtazapine led to favourable outcome. The encephalitis in this case is considered to have occurred secondarily to JCV infection in the presence of HTLV-1 infection. Therefore, it is crucial to investigate the presence of HTLV-1 in order to understand the aetiology of this brain inflammation.

HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP): Case based discussion of risk factors, clinical, and therapeutic considerations.

HTLV-1 is a retrovirus virus that infects CD4+ T cells. Most people with HTLV-1 infection remain asymptomatic but some may develop conditions such as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or adult T-cell leukemia/lymphoma. HAM/TSP is characterized by progressive spasticity and weakness of the lower extremities, as well as loss of bladder control and sensory disturbances. The risk of developing HAM/TSP is associated with the duration of infection and the proviral load. There is currently no cure for the disease but medications can help manage symptoms and slow the progression of the disease. This is the case of a 66-year-old female who presented with nonspecific symptoms of weakness and spasticity in a hospital in Connecticut and was subsequently diagnosed with HAM/TSP. The patient's diagnosis highlights the importance of considering diseases previously confined to specific endemic regions in a globalized world where increased emigration and population mixing can occur. Early identification and management of such cases is essential for optimizing patient outcomes and quality of life.

Screening for HTLV-1 infection should be expanded in Europe.

Human T-cell lymphotropic virus type 1 (HTLV-1) infection is spreading globally at an uncertain speed. Sexual, mother-to-child, and parenteral exposure are the major transmission routes. Neither vaccines nor antivirals have been developed to confront HTLV-1, despite infecting over 10 million people globally and causing life-threatening illnesses in 10% of carriers. It is time to place this long-neglected disease firmly into the 2030 elimination agenda. Current evidence supports once-in-life testing for HTLV-1, as recommended for HIV, hepatitis B and C, along with targeted screening of pregnant women, blood donors, and people who attended clinics for sexually transmitted infections (STIs). Similar targeted screening strategies are already being performed for Chagas disease in some Western countries in persons from Latin America. Given the high risk of rapid-onset HTLV-1-associated myelopathy, universal screening of solid organ donors is warranted. To minimize organ wastage, however, the specificity of HTLV screening tests must be improved. HTLV screening of organ donors in Europe has become mandatory in Spain and the United Kingdom. The advent of HTLV point-of-care kits would facilitate testing. Finally, increasing awareness of HTLV-1 will help those living with HTLV-1 to be tested, clinically monitored, and informed about transmission-preventive measures.

Distribución geográfica y tipo de infección del virus linfotrópico T humano en pacientes peruanos 2019-2021 / Geographic distribution and type of human T-lymphotropic virus (HTLV) infection in Peruvian patients 2019-2021

En el presente estudio describimos y caracterizamos la distribución geográfica de los casos positivos confirmados a HTLV-1 y 2 de pacientes peruanos con diagnóstico presuntivo entre 2019 y 2021. De un total de 555 muestras positivas confirmadas, 546 (98,4%) fueron HTLV-1 y 9 (1,6%) HTLV-2. Además, 22 de 24 departamentos del Perú presentaron casos de HTLV-1, siendo los principales motivos de solicitud de confirmación diagnóstica: aspirante a donar sangre con prueba de tamizaje reactivo, sospecha de leucemia/linfoma y paraparesia espástica tropical. Los resultados reflejan que la identificación de los puntos críticos constituye una brecha persistente respecto al diagnóstico, siendo cruciales para reducir el número de nuevos casos en Perú.

In the present study we describe and characterize the geographic distribution of HTLV-1 and 2 positive cases from Peruvian patients with presumptive diagnosis 2019 - 2021. Of a total of 555 confirmed positive samples, 546 (98.4%) were HTLV-1 and 9 (1.6%) HTLV-2. In addition, 22 of 24 departments of Peru presented cases of HTLV-1. The main reasons for requesting a confirmatory diagnosis being: aspiring to donate blood with a reactive screening test, suspicion of leukemia/ lymphoma and tropical spastic paraparesis. The results reflect that the identification of critical points constitutes a persistent gap regarding the diagnosis, being crucial to reduce the number of new cases in Peru.

Leucemia asociada al virus linfotrópico T humano tipo 1 (HTLV-1) y transmisión intrafamiliar de la infección en Santiago del Estero / Leukemia associated to human T cell lymphotropic virus type 1 (HTLV-1) infection and intrafamily transmission in Santiago del Estero

Resumen La leucemia/linfoma a células T del adulto (ATLL) es una enfermedad hematológica causada por el virus linfotrópico T humano tipo 1 (HTLV-1) que se desarrolla luego de 20 años de incubación, preferencialmente cuando la infección se adquiere por transmisión vertical. Este tiempo se reduce de 3 meses a 3 años cuando la transmisión del virus es por transfusión o trasplante de órganos. La ATLL aguda es de difícil diagnóstico por ser inusual y tener una rápida progresión a la muerte. En el Noroeste argentino, donde el virus es endémico, la ATLL es más frecuente, sin embargo, también se la detecta continuamente en el resto del país. El tratamiento de elección, en primera instancia, es el uso combinado de antivirales. Presentamos un caso de ATLL aguda desarrollada en un hombre de 59 años de Santiago del Estero a partir del cual se identificó transmisión intrafamiliar de la infección por HTLV-1.

Abstract Adult T-cell leukemia/lymphoma (ATLL) is an hematological disease caused by human T-cell lymphotropic virus type 1 (HTLV-1) that develops after 20 years of incubation preferentially when the infection is acquired by vertical transmission. In cases of transmission by transfusion or organ transplant, this time is reduced from 3 months to 3 years. Acute ATLL is difficult to diagnose because it is unusual and has a rapid progression to death. In the Argentine Northwest, where the virus is endemic, ATLL is more frequent, however it is also detected continuously in the rest of the country. The treatment of choice, in the first instance, is the combined use of antivirals. We present a case of acute ATLL developed in a 59-year-old man from Santiago del Estero from which intrafamilial transmission of HTLV-1 infection was identified.

Laboratory diagnosis of human T-lymphotropic virus in Brazil: assays, flowcharts, challenges, and perspectives

Abstract INTRODUCTION We present a data analysis and review of recent studies regarding the laboratory diagnosis of human T-lymphotropic virus 1 and 2 (HTLV-1/2) infections in Brazil. METHODS Target populations, available diagnostic serological assays (screening and complementary tests), molecular assays (in-house), causes of false-positive and false-negative results, and flowcharts were analyzed. RESULTS A table presents the target populations, two diagnostic flowcharts (depending on laboratory infrastructure and study population), and recent research that may improve how HTLV-1/2 is diagnosed in Brazil. CONCLUSIONS: Our results support the implementation of public policies to reduce HTLV-1/2 transmission and its associated diseases.

Brazilian protocol for sexually transmitted infections 2020: human T-cell lymphotropic virus (HTLV) infection

Abstract This article addresses the Human T-lymphotropic virus (HTLV). This subject comprises the Clinical Protocol and Therapeutic Guidelines for Comprehensive Care for People with Sexually Transmitted Infections, published by the Brazilian Ministry of Health. HTLV-1/2 infection is a public health problem globally, and Brazil has the largest number of individuals living with the virus. HTLV-1 causes several clinical manifestations of neoplasm (adult T-cell leukemia/lymphoma) and inflammatory nature, such as HTLV-1-associated myelopathy and other manifestations such as uveitis, arthritis, and infective dermatitis. These pathologies have high morbidity and mortality and negatively impact the quality of life of infected individuals. This review includes relevant information for health authorities professionals regarding viral transmission, diagnosis, treatment, and monitoring of individuals living with HTLV-1 and 2 in Brazil.

HTLV-2 infection in Manaus, Brazil: first description of HTLV-2c subtype in an urban area of the Western Amazon region

Abstract INTRODUCTION: We investigated the prevalence of human T-cell lymphotropic virus types 1 and 2 (HTLV-1/2) infection in patients with hematological diseases from the western Amazon region of Brazil. METHODS: Samples from 306 patients were submitted for the molecular diagnosis of HTLV-1/2 infection by real time PCR (qPCR), with amplification, sequencing, and phylogenetic analysis of the long terminal repeat (LTR) region. RESULTS: A 29-year-old male carrier of sickle cell anemia with a history of multiple blood transfusions was diagnosed with the HTLV-2c subtype. CONCLUSIONS: This study describes the first known occurrence of HTLV-2c in the urban area of Brazil's western Amazon region.

Specificity of HTLV screening tests and its impact on health care program costs: The perspective of antenatal screening in Brazil

Abstract INTRODUCTION: Brazil ranks first in the number of HTLV-1/-2-infected individuals worldwide. The high morbidity and mortality of HTLV-1-associated diseases, especially following infection in infancy, requires strong action to reduce vertical transmission. METHODS: To facilitate the appraisal of the implementation of the HTLV antenatal screening program by the Brazilian Ministry of Health, we determined the costs in distinct scenarios according to HTLV seroprevalence, specificity of the screening test, and type of confirmatory test. RESULTS: HTLV antenatal screening would cost R$ 55,777,012-R$ 77,082,123/year. Screening assays with high specificity reduce the need and cost of confirmatory assays by up to 25%. CONCLUSIONS: Careful selection of the screening assay is required to optimize the program.

Evaluación de dos marcas comerciales de pruebas de ELISA para el diagnóstico de HTLV-1 frente a muestras peruanas

Resumen Por ser el Perú un país endémico de HTLV-1, es importante conocer la confiabilidad de las marcas comerciales para el diagnóstico más usadas en nuestro país. En el presente estudio, evaluamos dos marcas comerciales de pruebas de ELISA (Biokit y Wantai) para la detección de anticuerpos contra HTLV-1 frente a muestras peruanas. Ambas marcas comerciales fueron evaluadas frente a 242 sueros: 123 positivos a HTLV-1 y 119 negativos a HTLV-1 (referencia: inmunoblot). Se estimaron los parámetros de precisión diagnóstica. La sensibilidad, especificidad, VPP, VPN e índice de validez de Biokit fueron: 100%, 93,2%, 93,8%, 100%, 96,6%; respectivamente y de Wantai fue de 99,1% para todos los parámetros. Concluimos, que la marca Biokit fue la más adecuada para ser usada en el Laboratorio de Referencia Nacional de Virus de Transmisión Sexual, VIH/SIDA de Perú.

Abstract As Peru is endemic to HTLV-1, it is important to know the reliability of the most used screening trademarks in our country. In the present study, we evaluated two brands of ELISA (Biokit and Wantai) for the detection of antibodies against HTLV-1/2 against Peruvian samples. Both brands were evaluated against 242 sera: 123 positive for HTLV-1 and 119 negative for HTLV-1 (Reference: Immunoblot). We estimated diagnostic accuracy parameters. The sensitivity, specificity, PPV, NPV and validity index of Biokit were: 100%, 93.2%, 93.8%, 100%, 96.6%; respectively and Wantai were 99.1% for all parameters. We conclude that the Biokit brand is the most suitable for use in the National Reference Laboratory of Sexually Transmitted Viruses HIV/AIDS, Peru.

Line immunoassay for confirmation and discrimination of human t-cell lymphotropic virus infections in inconclusive western blot serum samples from Brazil

Difficulties in confirming and discriminating human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by serological Western blot (WB) assays (HTLV Blot 2.4; MP Biomedicals) have been reported in Brazil, mainly in HIV/AIDS patients, with a large number of WB-indeterminate and WB-positive but HTLV-untypeable results. Nonetheless, a line immunoassay (LIA) (INNO-LIA HTLV-I/II; Fujirebio) provided enhanced specificity and sensitivity for confirming HTLV-1/2 infections. To add information concerning the improved ability of the LIA in relation to WB when applied to samples of individuals from different risk groups from Brazil, we performed the present study. Three groups were analyzed group 1 (G1), with 62 samples from HIV/AIDS patients from São Paulo, SP (48 WB indeterminate and 14 HTLV untypeable); group 2 (G2), with 24 samples from patients with hepatitis B or hepatitis C from São Paulo (21 WB indeterminate and 3 HTLV untypeable; 17 HIV seropositive); and group 3 (G3), with 25 samples from an HTLV outpatient clinic in Salvador, Bahia (16 WB indeterminate and 9 HTLV untypeable; all HIV seronegative). Overall, the LIA confirmed HTLV-1/2 infection (HTLV-1, HTLV-2, or HTLV) in 66.1% (G1), 83.3% (G2), and 76.0% (G3) of samples. Interestingly, the majority of WB-indeterminate results were confirmed by the LIA as being HTLV-2 positive in G1 and G2 but not in G3, in which the samples were defined as being HTLV-1 or HTLV positive. These results agree with the virus types that circulate in such patients of different regions in Brazil and emphasize that the LIA is the bes

Association of TLR3 single nucleotide polymorphisms with susceptibility to HTLV-1 infection in Iranian asymptomatic blood donors

Abstract INTRODUCTION: The human T-lymphotropic virus type 1 (HTLV-1) has a single-stranded RNA genome and expresses specific proteins that have oncogenic potential. Approximately 15 to 20 million people worldwide have been infected by this virus. Changes in protein or gene expression are the effects of single nucleotide polymorphisms (SNPs) within the Toll-like receptor 3 (TLR3) gene. The function and efficacy of signal transduction also lead to modified immune responses. The present study aimed to investigate the association of SNPs within TLR3 (rs3775291 and rs3775296) with susceptibility to HTLV-1 infection in Iranian asymptomatic blood donors. METHODS: This study was performed on 100 HTLV-1-infected asymptomatic blood donors and 118 healthy blood donors. Genomic DNA from all participants was purified and then amplified using specific PCR primers. SNPs within TLR3 were evaluated using the restriction fragmentation length polymorphism technique, and the results were analyzed using SPSS software (version 22). RESULTS: The frequencies of the TLR3 (rs3775296) CC, CA, AA genotypes were 70%, 24%, and 6% in the patient group, and 50.8%, 44.9%, and 4.2% in the control group, respectively. There was a significant difference in the frequency distribution of TLR3 (rs3775296) genotypes and alleles, but not in the frequency distribution of TLR3 (rs3775291) genotypes between the patient and control groups. CONCLUSIONS: The TLR3 SNP rs3775296 was significantly associated with HTLV-1 infection and may be a protective factor against this viral infection.

Neurologic complications of HTLV-1: a review / Complicações neurológicas do HTLV: uma revisão HTLV-1

The human T-cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that infects about 20 million people worldwide and causes immune-mediated diseases of the nervous system. The classical neurological presentation of HTLV-1 infection is the so-called HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, HAM/ TSP is not the only neurological outcome that can result from HTLV-1 infection. In this Review it is made an update on the many aspects of this important neurological condition, the HTLV-1 neurological complex.

O vírus linfotrópico de células T humanas tipo 1 (HTLV-1) é um retrovírus que infecta cerca de 20 milhões de pessoas em todo o mundo e causa doenças imunomediadas do sistema nervoso. A apresentação neurológica clássica da infecção pelo HTLV-1 é a chamada paraparesia espástica tropical / mielopatia associada ao HTLV-1 (HAM/TSP). HAM / TSP,no entanto, não é o único desfecho neurológico que pode resultar da infecção pelo HTLV-1. Nesta revisão, é feita uma atualização sobre vários aspectos desta importante condição neurológica, o complexo neurológico do HTLV-1.

Human T cell lymphotropic virus type 1 infection among men who have sex with men in Central Brazil

ABSTRACT Human T cell lymphotropic virus type 1 (HTLV-1) was the first retrovirus discovered in humans and is endemic in several parts of the world. Because of risk behaviors, mainly sexual, men who have sex with men (MSM) are at high risk of acquiring HTLV-1 infection. A cross-sectional study was performed to estimate the prevalence of HTLV-1 infection, to characterize genetically HTLV-1 sequences and to identify risk behaviors associated with this infection among MSM in Central Brazil. A total of 430 MSM were enrolled in this study and three were shown to be HTLV-1 infected, prevalence of 0.7% (95% confidence interval: 0.4-0.9). Phylogenetic analysis showed that all HTLV-1 positive samples belonged to Cosmopolitan subtype Transcontinental subgroup A. Although the prevalence rate of HTLV-1 infection found in this study was similar to that observed among Brazilian blood donors, additional HTLV-1 preventive interventions need to be further implemented because this population is engaged in high-risk sexual behavior.

Rendimiento diagnóstico de la prueba de inmunofluorescencia indirecta para la detección de anticuerpos contra HTLV-1 / Diagnostic performance of the indirect immunofluorescence test for the detection of antibodies against HTLV-1

RESUMEN El objetivo del estudio fue determinar el rendimiento diagnóstico de la prueba de inmunofluorescencia indirecta (IFI) para la detección de anticuerpos contra HTLV-1. Se realizó un estudio de evaluación de prueba diagnóstica. Se usaron cultivos celulares MT2 infectados con HTLV-1 y K-562 sin infección, luego fueron sembrados, fijados en láminas para inmunofluorescencia y enfrentados a sueros. Se usaron 155 sueros (80 positivos para HTLV-1 y 75 positivos para otras enfermedades) procedentes de la seroteca del Instituto Nacional de Salud del Perú. Adicionalmente, se evaluó la repetibilidad (en el laboratorio) y reproducibilidad (en laboratorios de costa, sierra y selva) de la prueba. La prueba IFI para la detección de anticuerpos contra HTLV-1 tuvo una sensibilidad de 98,75% (IC 95%: 95,69-100%), una especificidad de 98,67% (IC 95%: 95,40-100%) y el índice de kappa de 0,975. No hubo falsos positivos ni falsos negativos; sin embargo, sí se obtuvo un resultado indeterminado y uno inespecífico. La prueba mostró 100% de concordancia en la repetibilidad y reproductibilidad. Concluimos que los resultados obtenidos son comparables a la prueba de referencia. La prueba de IFI presenta un buen rendimiento diagnóstico y sería de utilidad para la confirmación de HTLV-1.

ABSTRACT The objective of the study was to determine the diagnostic yield of the indirect immunofluorescence (IFI) test for the detection of antibodies against HTLV-1. A diagnostic test evaluation study was performed. HTLV-1-infected MT2 cells and HTLV-1-uninfected K-562 cells were cultured; then these cells were impregnated and fixed in sheets for immunofluorescence and faced to Peruvian sera. A total of 155 sera (80 HTLV-1-positive sera and 75 sera positive for other diseases) from the Peruvian Instituto Nacional de Salud were used. In addition, the parameters of repeatability (intra-laboratory) and reproducibility (in laboratories of the Peruvian coast, mountains and jungle) of the test were evaluated. The IFI test detected the presence of antibodies against HTLV-1 reaching a sensitivity of 98.75% (95% CI: 95.69 - 100.00%), a specificity of 98.67% (95% CI: 95.40 - 100.00%) and the Kappa index was 0.975. There were no false positives or false negatives; however, one undetermined result and one non-specific result were obtained. The test showed 100% qualitative agreement when performing the repeatability and reproducibility. The results obtained are comparable to the reference test. Therefore, the IFI test had a good diagnostic performance and would be useful for the confirmation of HTLV-1.