Combination of Xpert® MTB/RIF and DetermineTM TB-LAM Ag improves the diagnosis of extrapulmonary tuberculosis at Jimma University Medical Center, Oromia, Ethiopia

PLoS One. 2022 Feb 3;17(2):e0263172. doi: 10.1371/journal.pone.0263172. eCollection 2022.

Abstract

Background: Ethiopia is one of the high burden countries for extrapulmonary tuberculosis (EPTB); however, the prompt diagnosis of EPTB remains challenging. This study is aimed to evaluate the diagnostic performance of Xpert MTB/RIF and DetermineTM TB-LAM Ag (TB-LAM) for the prompt diagnosis of EPTB in Ethiopia.

Methods: A total of 147 presumptive EPTB patients, including 23 HIV- positive participants were enrolled. Extra-pulmonary samples were collected from all presumptive EPTB cases and tested for Mycobacterium tuberculosis complex (MTBC) using fluorescent microscopy, Xpert MTB/RIF, and culture. Additionally, urine samples were also collected from 126 participants and were tested by DetermineTM TB-LAM Ag (Alere Inc, Waltham, USA). The Sensitivity and specificity of Xpert and TB- LAM tests were calculated by comparing with a composite reference standard (CRS), which comprises smear microscopy, culture and response to empirical anti-TB treatment.

Results: Of 147 patients, 23 (15.6%) were confirmed EPTB cases (culture-positive), 14 (9.5%) were probable EPTB (clinically, radiologically or cytologically positive and received anti-TB treatment with good response), and 110 (74.8%) were classified as "non- TB" cases. Compared to the composite reference standard (CRS), the overall sensitivity and specificity of Xpert MTB/RIF were 43.2% and 100%, respectively with the highest sensitivity for Lymph node aspirate (85.7%) and lower sensitivity for pleural fluid (14.3%) and 100% specificity for all specimen types. The sensitivity and specificity of TB-LAM were 33.3% and 94.4% respectively with the highest sensitivity for HIV co-infected participants (83.3%). The sensitivity of the combination of Xpert MTB/RIF and TB-LAM tests regardless of HIV status was 61.1% whereas the sensitivity was improved to 83.3% for HIV-positive cases.

Conclusion: TB-LAM alone has low sensitivity for EPTB diagnosis; however, the combination of TB-LAM and Xpert MTB/RIF improves the diagnosis of EPTB particularly for countries with high EPTB and HIV cases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Coinfection* / diagnosis
  • Coinfection* / epidemiology
  • Coinfection* / etiology
  • Female
  • HIV / isolation & purification
  • HIV Infections* / complications
  • HIV Infections* / virology
  • Humans
  • Male
  • Mycobacterium tuberculosis* / genetics
  • Mycobacterium tuberculosis* / immunology
  • Mycobacterium tuberculosis* / isolation & purification
  • Polymerase Chain Reaction* / methods
  • Sequence Analysis, DNA
  • Tuberculosis, Pulmonary* / diagnosis
  • Tuberculosis, Pulmonary* / epidemiology
  • Tuberculosis, Pulmonary* / etiology
  • Urinalysis* / methods
  • Young Adult

Grants and funding

This work was supported by Jimma University-Mycobacteriology Research Center, Jimma, Ethiopia. The funders had no role in study design, data acquisition, analysis and interpretation, or the decision to prepare the manuscript and submit for publication.