Diagnostic Yield of Xpert MTB/RIF Assay Using Bronchoalveolar Lavage Fluid in Detecting Mycobacterium tuberculosis among the Sputum-Scarce Suspected Pulmonary TB Patients

Abstract

Tuberculosis (TB) remains one of the leading causes of death worldwide and is caused by the single infectious agent Mycobacterium tuberculosis (Mtb). Although sputum is the most common specimen for pulmonary TB detection, some other respiratory specimens, such as bronchoalveolar lavage (BAL) fluid, gastric lavage (GL), and induced sputum (IS), are also collected from patients who are unable to deliver sputum. In this study, we aimed to evaluate the diagnostic performances of different test methods for TB diagnosis using BAL fluid specimens from sputum-scarce pulmonary TB patients. In this current study, a total of 210 BAL fluid specimens were collected and subjected to culture on Lowenstein–Jensen (L-J) medium, using an N-acetyl-L-cysteine-Sodium Hydroxide decontamination and digestion method, Xpert MTB/RIF (Xpert, Cepheid, Sunnyvale, CA, USA) assay, and acid-fast bacilli (AFB) microscopy with a Ziehl–Neelsen staining method for the detection of pulmonary TB. The sensitivity and specificity of these methods were then analyzed against the composite reference standard (CRS). Additionally, the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of these assays. Among the 210 specimens, 39 (18.6%), 27 (12.8%), and 12 (5.7%) were found positive with Xpert assay, culture, and AFB microscopy, respectively. Considering the CRS, 42 (20%) were positive as the final diagnosis. The Xpert assay had a significantly higher sensitivity (92.9%, 95% CI: 80.5–98.5) compared to culture (64.3%, 95% CI: 48.0–78.4) and AFB microscopy (28.6%, 95% CI: 15.7–44.6) against the CRS. Additionally, the area under the ROC curve (AUC) for the Xpert assay, culture, and AFB microscopy accounted for 0.964, 0.821, and 0.655, respectively, when using CRS as the reference. In conclusion, our study findings demonstrated that the Xpert assay conferred a considerable diagnostic potential compared to other conventional methods for the diagnosis of pulmonary TB from BAL fluid specimens.

Performance of the MeltPro TB assay as initial test for diagnosis of pulmonary tuberculosis with drug-resistance detection

“…In this study, the sensitivity of MeltPro for diagnosing PTB in sputum, BALF, and pulmonary puncture fluid was 65.4%, 81.3%, and 71.0%, respectively; all of which were comparable to Xpert's performance. Prior studies have shown that both conventional detection methods and new molecular rapid diagnostic tests for PTB diagnosis in BALF specimens offer promising diagnostic potential compared to sputum specimens (Badr et al 2022;Uddin et al 2022). The current study's findings further support this notion, emphasizing the potential benefits of using bronchoscopy to collect BALF from patients with presumptive PTB for MeltPro testing to enhance diagnostic sensitivity.…”

Clinical application of metagenomic next-generation sequencing in tuberculosis diagnosis

“…Acid-fast staining relies on the high number of bacteria present in the sputum to give accurate results. Several studies have shown that the sensitivity of acid-fast staining can be as low as 8% or as high as 55.68% ( Qiu et al., 2022 ; Stadelman et al., 2022 ; Uddin et al., 2022 ; Zhang et al., 2022 ). Although mNGS is slightly more sensitive than T-SPOT.TB assay, for TB, a trade-off from a cost/time perspective would be beneficial.…”

Diagnostic Performance of Different Laboratory Methods for the Detection of Extrapulmonary Tuberculosis

“…The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the overall performances of all the diagnostic methods compared to the composite reference standard (CRS) using RStudio version 1.4. The CRS-positive was considered for confirmed positive cases in any of AFB microscopy, culture, and molecular methods (Xpert MTB/RIF and MTBDRplus) [21]. The AUC with >0.5 to <0.7 demonstrated a low diagnostic value, ≥0.7 to <0.9 demonstrated a moderate diagnostic value, and ≥0.9 demonstrated a high diagnostic value [22].…”