Molecular identification of non-tuberculous mycobacterial species isolated from extrapulmonary samples using real-time PCR and rpoB sequence analysis

Targeted nanopore sequencing using clinical specimens for the rapid diagnosis of extrapulmonary tuberculosis

BACKGROUND

The clinical presentation of extrapulmonary tuberculosis (EPTB) is atypical and it is easily confused with other diseases such as common infections, making prompt diagnosis a great challenge. This study aimed to evaluate the accuracy of targeted nanopore sequencing (TNS) in the diagnosis of EPTB. The diagnostic accuracy of TNS using different types of extrapulmonary specimens was also evaluated.

METHODS

We reviewed the clinical data of patients with suspected EPTB for whom TNS was conducted and who were hospitalized at our center. The true positive, false positive, false negative, and true negative values were determined. Indices of diagnostic accuracy were computed, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) for TNS and acid-fast bacilli (AFB) culture, and compared with those from clinical diagnosis.

RESULTS

149 patients were included in the analysis. The overall sensitivity, specificity, PPV, NPV, and AUC of TNS for the diagnosis of EPTB were 86.4%, 87.5%, 97.3%, 55.3%, and 0.87, respectively. For diagnosis by AFB culture, these values were 25.6%, 100.0%, 100.0%, 20.5%, and 0.63, respectively. The most common specimens used were lymph node tissue, cerebrospinal fluid, pleural effusion, and pleural tissue. The diagnostic accuracy of TNS using all types of extrapulmonary specimens was good.

CONCLUSIONS

TNS demonstrates good diagnostic accuracy in the rapid diagnosis of EPTB and this was true across different types of extrapulmonary specimens.

Incorporating direct molecular diagnostics in management algorithms for nontuberculous mycobacteria: Is it high time?

Nontuberculous mycobacteria (NTM) are a group of acid-fast mycobacteria other than Mycobacterium tuberculosis complex (MTBC) that cause pulmonary disease that is similar to the disease caused by MTBC. International guidelines for the diagnosis of pulmonary NTM disease are rigid and have remained unchanged for nearly 2 decades. In this opinion piece, we provide a new perspective on the traditional criteria by suggesting a diagnostic algorithm that incorporates direct molecular identification of NTM performed on raw sputum specimens (using Sanger or targeted deep sequencing approaches, among others) paired with traditional culture methods. Our approach ensures a more rapid diagnosis of pulmonary NTM disease, thus, facilitating timeous clinical diagnosis, and prompt treatment initiation, where indicated, and leverages recent advances in novel molecular techniques into routine NTM identification practice.