RESUMO
INTRODUCTION: Tuberculosis (TB) is one of the most prevalent respiratory diseases in the world. In 2020 there were at least 9.9 million new infections, with 1.5 million deaths. Approximately 10% of people infected with Mycobacterium tuberculosis develop the disease during the first 2 to 5 years after infection. In South America, the diagnosis of Latent Tuberculosis Infections (LTBI) continues to be performed through the Mantoux tuberculin skin test (TST). OBJECTIVE: The objective of our study was to compare the sensitivity of a new immunofluorescence IGRA test against a widely available IGRA kit on the market. MATERIAL AND METHOD: Close contact with infectious TB patients, HIV patients, or immunocompromised for another cause were recruited. Two interferon-gamma release assay (IGRA) diagnostic kits were used and compared with TST. RESULTS: 76 patients were recruited, 93.42% were Chilean nationality, and 98.68% of the patients did not have immunosuppression. The sensitivity of the new technique was 88.89%, and the specificity was 92.50% in the study population compared to the IGRA previously used. In the subgroup older than 36 years, the sensitivity was 95.65%, and the specificity was 89.47%. CONCLUSION: IGRA techniques are a new resource in clinical laboratories to make an accurate diagnosis of LTBI in the region of the Americas. In our population, the greatest benefit of this new IGRA would be observed in people over 36 years of age, where the sensitivity of the technique was like that of the currently available test.
RESUMO
La nueva norma técnica para el control y la eliminación de la tuberculosis es un gran avance para el diagnóstico de este microorganismo en Chile. Actualmente la principal técnica microbiológica para el diagnóstico de laboratorio es la biología molecular, que reduce el tiempo del resultado a tan solo un par de horas. La normativa actual indica que en el paciente caso presuntivo de tuberculosis (CPT) la técnica exclusiva a realizar es Biología molecular. La literatura indica que la detección a través de amplificación de material genético de la micobacteria tiene un límite de detección de 15,6 UFC/ ml, por tanto, todas las muestras bajo ese límite umbral potencialmente podrían no ser diagnosticadas bajo esta estructura emanada por el ministerio de Salud en Chile. Nuestra recomendación es continuar con el estudio de cultivo en medios líquidos o sólidos para todas las muestras hasta obtener literatura que avale lo contrario
The new technical standard for the control and elimination of tuberculosis in Chile is a great advance for the diagnosis of this microorganism. Currently the main microbiological technique for laboratory diagnosis is PCR, which reduces the time to result to just a couple of hours. The current regulations indicate that in the patient with a presumptive case of tuberculosis (CPT) t he exclusive technique to be performed is PCR. The literature indicates that the detection through amplification of genetic material of the mycobacterium has a detection limit of 15.6 CFU/ml, therefore, all samples under this threshold limit could potentially not be diagnosed under this structure emanated by the Ministry of Health in Chile. Our recommendation is to continue with the study of culture in liquid or solid media for all samples until literature confirms otherwise
