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. 2020 Jan 13;20(1):33.
doi: 10.1186/s12879-019-4749-x.

Diagnostic accuracy of the Xpert MTB/Rif Ultra for tuberculosis adenitis

Katherine Antel  1 , Jenna Oosthuizen  2 , Francois Malherbe  3 , Vernon J Louw  2 , Mark P Nicol  4 , Gary Maartens  5 , Estelle Verburgh  2
Affiliations

Diagnostic accuracy of the Xpert MTB/Rif Ultra for tuberculosis adenitis

Katherine Antel et al. BMC Infect Dis. .

Erratum in

Abstract

Background: The WHO recently recommended the new Xpert MTB/RIF Ultra assay (Ultra) instead of the Xpert MTB/RIF assay because Ultra has improved sensitivity. We report the diagnostic accuracy of Ultra for tuberculous adenitis in a tuberculosis and HIV endemic setting.

Methods: We obtained fine-needle aspirates (FNA) and lymph node tissue by core-needle biopsy in adult patients with peripheral lymphadenopathy of >20 mm. Ultra and mycobacterial culture were performed on FNA and tissue specimens, with histological examination of tissue specimens. We assessed the diagnostic accuracy of Ultra against a composite reference standard of 'definite tuberculosis' (microbiological criteria) or 'probable tuberculosis' (histological and clinical criteria).

Results: We prospectively evaluated 99 participants of whom 50 were HIV positive: 21 had 'definite tuberculosis', 15 'probable tuberculosis' and 63 did not have tuberculosis (of whom 38% had lymphoma and 19% disseminated malignancy). Using the composite reference standard the Ultra sensitivity on FNA was 70% (95% CI 51-85; 21 of 30), and on tissue was 67% (45-84; 16/24) these were far superior to the detection of acid-fast bacilli on an FNA (26%; 7/27); AFB on tissue (33%; 8/24); or tissue culture (39%; 9/23). The detection of granulomas on histology had high senstivity (83%) but the lowest specficity. When compared with culture the Ultra on FNA had a sensitvity of 78% (40-97; 7/9) and tissue 90% (55-100; 9/10).

Conclusions: Ultra performed on FNA or tissue of a lymph node had good sensitivity and high specificity. Ultra had a higher yield than culture and has the advantage of being a rapid test. Ultra on FNA would be an appropriate initial investigation for lymphadenopathy in tuberculosis endemic areas followed by a core biopsy for histopathology with a repeat Ultra on tissue if granulomas are present.

Keywords: Core needle biopsy; Fine-needle aspiration; HIV; Tuberculosis; Xpert MTB/RIF Ultra.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Study procedures
Fig. 2
Fig. 2
Trial profile. MTB = Mycobacterium tuberculosis. AFB = acid fast bacilli. FNA = fine-needle aspirate
Fig. 3
Fig. 3
Venn diagram to show the overlap in yield in the tests with the highest yeild for tuberculous adenitis. TB = tuberculosis; FNA = fine-needle aspirate
See this image and copyright information in PMC

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