Skip to main content

Open Access Prevalence and interpretation of Xpert® Ultra trace results among presumptive TB patients

BACKGROUND: The “trace call” results on Xpert® Ultra indicates extremely low TB levels and may be difficult to interpret. The prevalence of trace results among presumptive TB patients in high TB-HIV infection settings is unknown, as is the significance of divergent “trace call” result interpretations.

METHODS: Presumptive TB patients attending a public health facility in Lusaka, Zambia, were prospectively enrolled. Participants underwent several TB investigations, including sputum smear microscopy, Ultra testing, and culture. The diagnostic accuracy of Ultra (culture-based reference) and the number of patients recommended for TB treatment was assessed according to several different interpretation criteria for “trace call” results.

RESULTS: Among the 740 participants, 78 (10.5%) were Ultra-positive and an additional 37 (5.0%) had a “trace call” result. The prevalence of trace results did not differ according to HIV status (5.3% vs. 4.8%) or prior TB status (5.6% vs. 4.9%). Differing interpretations of trace results had modest effects on Ultra’s sensitivity (range 79.3–82.6%) and specificity (range 94.3–99.2%), but increased the number of patients recommended for treatment by up to 44.9%.

CONCLUSIONS: Ultra trace results were common in this setting. The interpretation of trace results may substantially impact TB case yield.

Keywords: CAD; HIV; diagnosis; tuberculosis

Document Type: Research Article

Affiliations: 1: Centre for Infectious Disease Research in Zambia, TB Department, Lusaka Zambia 2: Division of HIV, Infectious Diseases and Global Medicine Zuckerberg San Francisco General Hospital and Trauma Center University of California, San Francisco, San Francisco, CA, USA

Publication date: March 21, 2022

More about this publication?
  • Public Health Action (PHA), The Union's quarterly Open Access journal, welcomes the submission of articles on operational research. It publishes high-quality scientific research on health services, providing new knowledge on how to improve access, equity, quality and efficiency of health systems and services.

    The Editors will consider any manuscript reporting original research on quality improvements, cost-benefit analysis, legislation, training and capacity building, with a focus on all relevant areas of public health (e.g. infection control, nutrition, TB, HIV, vaccines, smoking, COVID-19, microbial resistance, outbreaks etc).

  • Editorial Board
  • Information for Authors
  • International Journal of Tuberculosis and Lung Disease
  • Public Health Action
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content