Análise do ensaio imunológico igra versus prova tuberculínica para detecção de infecçção latente por Mycobacterium tuberculosis em pacientes HIV positivos

Orientadora: Profª. Drª. Sonia Mara RaboniCo-orientadora: Profª. Drª. Libera Maria Dalla CostaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Saúde, Programa de Pós-Graduação em Medicina Interna. Defesa : Curitiba, 31/10/2014Inclui referênciasResumo: Indivíduos infectados com M. tuberculosis (MTB) sem doença ativa têm infecção latente por tuberculose (ILTB). Pacientes portadores de HIV, por serem imunodeprimidos, são mais propensos a desenvolver TB ativa. A identificação da ILTB permite a intervenção precoce com o uso de quimioprofilaxia e, consequentemente, contribui para uma menor morbidade e mortalidade neste grupo de pacientes. A prova tuberculínica (PT) mantém-se como o método padrão-ouro para diagnóstico de ILTB, apesar de apresentar limitações técnicas. O objetivo deste estudo foi avaliar o desempenho do teste imunológico QuantiFERON TB Gold In Tube®, que se baseia na avaliação da resposta do gama interferon para antígenos específicos de MTB, para diagnóstico de ILTB em pacientes com HIV residentes em um país com alta incidência de tuberculose, comparando estes achados com os resultados da PT. Realizou-se um estudo de Coorte, que incluiu 140 pacientes, que foram acompanhados por um período médio de 12 meses (6 a 21 meses). Um total de 115 (82%) e nove (6,4%) pacientes apresentou ambos os testes negativos e positivos, respectivamente. Entre os resultados discordantes observou-se em 12 (8,6%) pacientes IGRA positivo com PT negativa e em quatro (3%) pacientes resultados de IGRA negativo com PT positiva. O coeficiente de Cohen Kappa foi de 0,214, mostrando uma concordância pobre entre as duas técnicas. Comparando os resultados obtidos em ambos os testes, pode-se verificar que não houve evidência estatística de que um ou outro método seja superior (p = 0,08). Não foi observada nenhuma correlação entre os resultados de IGRA e PT e os valores de LT CD4+, embora em pacientes com maior imunossupressão (LT CD4+ <300 células/mm3) observamos testes IGRA positivos e PT não reatoras. No período de acompanhamento, um paciente que apresentava PT e IGRA negativos evoluiu para morte por septicemia, e outro com resultados discordantes (IGRA+/PT-) apresentou conversão da PT. Avaliando as características de desempenho do IGRA, considerando PT como o teste padrão-ouro, a sensibilidade observada foi em torno de 70%, com especificidade de 90%. Considerando os resultados de ambos os testes como verdadeiro positivo, um aumento de 8% na positividade pode ser observado. O tratamento da ILTB neste grupo de pacientes poderá ter impacto sobre a taxa de tuberculose ativa e sobrevivência de portadores do HIV, porém isso ainda precisa ser avaliado ao longo dos anos. Palavras-chave: HIV, Mycobacterium tuberculosis, teste tuberculínicoAbstract: Individual infected with M. tuberculosis (MTB) without active disease can present latent tuberculosis infection (LTBI). These patients in the context of impaired immune systems, such as HIV+, are more likely to progress to active TB. Identification of LTBI allows early intervention with the use of chemoprophylaxis, consequently contributing to a lower morbidity and mortality in this group of patients. Tuberculin skin test (TST) has remained as gold standard method to diagnosis LTBI, despite it presents technical limitations. The aim of this study was to assess the performance of the new immunological test Quantiferon TB Gold in tube, which is based on evaluating the IFN-gamma response to specific MTB antigens, to LTBI diagnosis on HIV patients from a country with high-tuberculosis burden, comparing the findings with TST results. It was a cohort study that included 140 patients, who are followed up for 21 months. A total of 115 (82%) and 9 (6.4%) patients had both tests negative and positive, respectively. Disagreement results occurred in 12 (8.6%) patients, whom had IGRA positive with negative TST and 4 (3%) patients that showed positive TST with negative IGRA. The Cohen Kappa coefficient found was 0.214, showing a poor concordance between both techniques. Comparing the results obtained by both tests, there was no statistical evidence that either method is different, because of the discrepancies occurred in a statistically identical manner (p = 0,08). None correlation between the results and CD4+ LT values was observed, though in patients with lowers CD4+ LT values (<300 cell/mm3) only IGRA tests were positive. In the period of follow up one patient, that presented both negative tests, evolved to death from sepsis, and another with discordant results (IGRA+/TST-) presented TST conversion. Evaluating the operational characteristics of IGRA, considering TST as the gold standard test, the sensitivity observed was around 70% and the specificity 90%. Considering the results of both tests as true positive an incremental of 8% in the positivity could be observed. If the LTBI treatment in this group of patients will have some impact on the rate of active tuberculosis and survival of HIV carriers still need to be evaluated over the years. Keywords: HIV, Mycobacterium tuberculosis, tuberculin skin test

Research on antimicrobial residues activity in urine samples of hospitalized patients

Introduction:Urinary tract infection is quite frequent in a hospital environment, and the urine culture is the gold standard for diagnosis of this disease, because it allows bacterial identification and performing antimicrobial susceptibility testing. Culturenegative urine samples result of patients with strong suspicion of infection may occur due to the activity of antimicrobial residues, which can interfere with bacterial growth in vitro and produce false-negative results.Objective:Verify the occurrence of falsenegative urine cultures due to the presence of antimicrobial residues in samples of patients admitted to the Clinical Hospital of Paraná Federal University.Material and methods:A total of 188 urine samples from hospitalized patients were randomly selected, during the period from July to December 2012. All samples were evaluated on the result of the urine culture, bacteriuria, and research on residues of antimicrobial activity by manual and automated techniques.Results:44 (23.4%) presented positive urine culture, 121 (64.4%) negative urine culture, and 23 (12.2%) presented growth of many species. In 14 samples, negative urine cultures associated with the presence of bacteria and were positive for the research on antimicrobial residues activity (RARA), were observed.Conclusion:Automated technique showed better performance when compared to manual technique, with sensitivity of 92.8% and 71.4%, respectively. The presence of antimicrobial residues may affect the recovery of bacteria in the urine, producing a false-negative result

Interferon-gamma release assay versus tuberculin skin test for latent tuberculosis infection among HIV patients in Brazil

Setting: Patients HIV+ attending in a reference clinic, Southern Brazil. Objective: To compare the interferon-gamma-release assay (IGRA – QuantiFERON® TB Gold In-Tube) with the tuberculin skin test (TST – PPD-Rt 23) for latent tuberculosis infection (LTBI) in patients with HIV. Design: Cohort study. Patients were simultaneously submitted to the TST and blood collection for the IGRA. Results: A total of 140 subjects were included. Nine (6.4%) were IGRA+/TST+, 12 (8.6%) were IGRA+/TST−, 4 (3%) were IGRA−/TST+, and 115 (82%) IGRA−/TST−. There was poor agreement between tests (kappa = 0.2), and no correlation between these results and CD4+ T lymphocyte counts. During follow-up, one patient with negative results on both tests died from sepsis, and another with discordant results (IGRA+/TST−) exhibited TST seroconversion. Compared to the TST, IGRA showed a sensitivity and specificity of 69% and 90%, respectively. The IGRA detected 8% more positive results than the TST. All patients were followed up for 2 years. Conclusion: The higher accuracy of the IGRA would result in LTBI treatments being administered to patients who would have otherwise been overlooked, decreasing the number of active tuberculosis cases. The long-term survival of HIV carriers requires further evaluation. Keywords: Mycobacterium tuberculosis, Immunological tests, Immunocompromised patient

The Xpert® MTB/RIF diagnostic test for pulmonary and extrapulmonary tuberculosis in immunocompetent and immunocompromised patients: Benefits and experiences over 2 years in different clinical contexts.

Xpert® MTB/RIF has been widely used for tuberculosis (TB) diagnosis in Brazil, since 2014. This prospective observational study aimed to evaluate the performance of Xpert in different contexts during a two-year period: (i) laboratory and clinical/epidemiological diagnosis; (ii) HIV-positive and -negative populations; (iii) type of specimens: pulmonary and extrapulmonary. Overall, 924 specimens from 743 patients were evaluated. The performance of the assays was evaluated considering culture (Lowenstein Jensen or LJ medium) results and composite reference standard (CRS) classification as gold standard. According to CRS evaluation, 219 cases (29.5%) were classified as positive cases, 157 (21.1%) as 'possible TB', and 367 (49.3%) as 'not TB'. Based on culture, Xpert and AFB smear achieved a sensitivity of 96% and 62%, respectively, while based on CRS, the sensitivities of Xpert, AFB smear, and culture were 40.7%, 20%, and 25%, respectively. The pooled sensitivity and specificity of Xpert were 96% and 94%, respectively. Metric evaluations were similar between pulmonary and extrapulmonary samples against culture, whereas compared to CRS, the sensitivities were 44.6% and 29.3% for the pulmonary and extrapulmonary cases, respectively. The Xpert detected 42/69 (60.9%) patients with confirmed TB and negative culture on LJ medium, and 52/69 (75.4%) patients with negative AFB smear results. There was no significant difference in the diagnostic accuracy based on the types of specimens and population (positive- and negative-HIV). Molecular testing detected 13 cases of TB in culture-negative patients with severe immunosuppression. Resistance to rifampicin was detected in seven samples. Herein, Xpert showed improved detection of pulmonary and extrapulmonary TB cases, both among HIV-positive and -negative patients, even in cases with advanced immunosuppression, thereby performing better than multiple other diagnostic parameters