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

Abstract

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.

Diagnosis of extrapulmonary tuberculosis by ultrasound-guided biopsy: A retrospective comparison study

“…( Limper et al., 2017 ), and this may affect the specificity of detection of MTB (decreased specificity in this study: culture 5%; smear 8%; HE 23%; AFB 27%). However, Xpert maintained high sensitivity (>95%) and specificity (nearly 100%) in both HIV-positive and -negative patients, consistent with previous reports (sensitivity: >80%; specificity: 97-99%) ( Horne et al., 2019 ; Tomaz et al., 2021 ). Finally, we evaluated the performance of different assays in smear-negative samples, and Xpert still had higher sensitivity (92.7% [80.6-97.5]) and specificity (100% [95.7-100]) compared to culture.…”

Evaluación del rendimiento del ensayo GeneXpert MTB/RIF en muestras con sospecha de tuberculosis extrapulmonar recibidas en el C.H.DR.A.A.M. de enero 2020-diciembre 2021

“…También se obtuvo, cinco (5) muestras con GeneXpert positivo y cultivo negativo, podemos inferir la toma de antibióticos antifímicos previos al muestreo, puesto que la historia clínica de dichos pacientes muestra antecedentes de TBP y al tratarse de una prueba molecular, GeneXpert puede detectar micobacterias no viables, es decir, el material genético de bacilos muertos puede permanecer tiempo después del tratamiento. (Kohli et al, 2018b;Mechal et al, 2019;De Oliveira Tomaz et al,2021).…”

Increased Detection of Mycobacterium tuberculosis Disease Using a Tissue-Based Laboratory-Developed Polymerase Chain Reaction Assay Compared to Standard Diagnostics

“…As such, a composite reference standard (CRS) based on a combination of these factors has been proposed as a barometer for diagnosis, particularly for culture-negative MTB. [14][15][16][17][18][19] We performed a retrospective study of patients with clinically suspected active MTB disease for whom an in-house, tissue-based MTB real-time PCR (MTB PCR) was performed on either pulmonary, pleural, or lymph node tissue at Yale New Haven Hospital Systems in New Haven, CT, from 2011 to 2019. 20,21 A chart review was performed to extract 1) clinical data; 2) epidemiologic data; 3) radiographic data; and 4) laboratory data including AFB stain and culture, Xpert, adenosine deaminase (ADA), send-out tests, and MTB PCR results.…”