Retrospective observational study of diagnostic accuracy of the Xpert® MTB/RIF assay on fiberoptic bronchoscopy sampling for early diagnosis of smear-negative or sputum-scarce patients with suspected tuberculosis

Abstract

BackgroundFiberoptic bronchoscopy (FOB) is a useful diagnosis tool in low-burden countries for patients with suspected pulmonary tuberculosis (TB) who are smear-negative or sputum-scarce. This study sought to determine the accuracy of the Xpert® MTB/RIF (XP) assay using FOB samples.MethodsWe retrospectively reviewed clinical, radiological, and microbiological characteristics of 175 TB-suspected patients requiring diagnostic FOB (bronchial aspirate or bronchoalveolar lavage) with XP assay. Polymerase chain reaction (PCR) and smear microscopy (SM) performances were first compared to culture, then to the final diagnosis, established based on clinical or radiological evolution when cultures were negative.ResultsOf the total 162 included patients, 30 (18.5%) had a final diagnosis of pulmonary TB, with positive cultures reported in 23. As compared to culture, sensitivity and specificity values were 80.0% and 98.6% for the XP assay, and 25.0% and 95.8% for SM, respectively. As compared to final diagnosis, the corresponding performance values were 60.0% and 100.0% for the XP assay, and 16.7% and 95.5% for SM, respectively. The sensitivity of the XP assay was significantly higher than that of SM in both cases (p = 0.003 and p = 0.001). Concerning the final diagnosis, both XP assay and culture sensitivities were similar (60% vs. 66.7%). PCR assay enabled pulmonary TB to be diagnosed earlier in 13 more cases, compared to SM.ConclusionOur study has confirmed the clinical benefits provided by XP assay compared to SM for the early diagnosis of suspected pulmonary TB cases requiring FOB, on per procedure samples, especially in a low TB-burden country.

Bronchial wash Gene Xpert MTB/RIF in lower lung field tuberculosis: Sensitive, superior, and rapid in comparison with conventional diagnostic techniques

“…Similar yields were documented in studies by Pierrae et al [31] as 25%, Bernard DA et al [32] as 41%, and Khalil KF et al [33] as 39.53%.…”

“…Culture of bronchoscopy sample for MTB was not done because of time factor, cumbersome, and cost effectiveness. Similar yields were documented in studies by Pierrae et al [31] as 80%, Bernard et al [32] as 92.3%, Khalil et al [33] as 91.86%, Lee et al [34] as 81.6%, and Surendra et al [35] as 90%, and few other studies [36][37][38][39] from various authors documented sensitivity between 57% and 75%.…”

To Study the Usefulness of Cbnaat (Cartridge Based Nuclear Acid Amplification Test) in Bal (Bronchoalveolar Lavage) Samples in the Diagnosis of Smear-Negative/Non Sputum Producing Patients With Suspected Tuberculosis

“…In a similar study from France Le Palud et al in 2014 found cough (51.9%) as the main symptom followed by general symptoms (45.1%). 12 In majority of patients in our study more than two symptoms were present. The most common lesions detected by chest imaging were consolidation (33.3%) and fibrocavitary diseases (11.1%).…”

“…Chest imaging was normal in 9.7% cases, whereas in study by Le Palud et al nodules (53.7) were the most common radiological finding followed by Pneumonia (27.1%). 12 Out of 72 clinico-radiologically suspected patients, only 3 were BAL smear positive while another 34 were further detected by CBNAAT giving a total bacteriological figure of 37. Out of 34 CBNAAT positive samples, 3 were resistant to Rifampicin.…”

Evaluation of Cbnaat in the Diagnosis of Smear Negative Tuberculosis in a Tertiary Care Hospital

“…In majority of the studies, microscopy sensitivity ranged from 22% to 41% and specificity from 95% to 100% which is similar to our study findings. (5,6,7) In Agarwal et al (8) study for smear negative samples, the sensitivity and specificity of GeneXpert was 79.1% and 93.1%. Many other studies have the sensitivities and specificities in the range of 57% -75% and 97% -100% respectively.…”