Elsevier

Tuberculosis

Volume 102, January 2017, Pages 1-2
Tuberculosis

Gene Xpert MTB/RIF assay for the diagnosis of intra-ocular tuberculosis from vitreous fluid samples

https://doi.org/10.1016/j.tube.2016.11.002Get rights and content

Introduction

The Gene Xpert MTB/RIF assay (GX) has been described as ‘a major step forward in tuberculosis diagnostics’ [1], [2]. Although GX has proved its worth in pulmonary [3] and various extra-pulmonary forms of tuberculosis [4], there is no data regarding its use in vitreous fluid (VF) samples from patients suspected of intra-ocular tuberculosis (IOTB). The present study investigated the potential of GX in an otherwise challenging diagnosis of presumed IOTB.

Section snippets

Methods

After approval by the Institute's Ethics committee, GX was performed on 165 VF samples collected from eyes undergoing pars plana vitrectomy. Study group (n = 85) had patients of presumed ocular tuberculosis based on the criteria described previously [5] while control group had patients with either non-tubercular intra-ocular inflammation (n = 50) or non-inflammatory vitreoretinal disorders (n = 30). Approximately 1 ml of VF was collected, 500μl of which was subjected to GX in accordance with

Results

GX detected M. tuberculosis complex in 19/85 (22.3%) cases from study group and none from the control group. The overall sensitivity, specificity, positive predictive value and negative predictive value of GX was 22.3%, 100%, 100% and 43.1%, respectively. 16/19 (84.2%) positive cases were rifampicin sensitive and 3/19 (15.8%) were rifampicin resistant by GX. rpoB gene sequencing reported 17 cases as rifampicin-sensitive while rifampicin resistance was revealed in two cases, at codons 516 and

Discussion

GX showed a sensitivity and specificity of 22.3% and 100%, respectively. While studies on CSF have documented the sensitivity of GX to range from 33% [4] to 59% [10], the sensitivity of GX for pleural fluid ranges from 5% [11] to 33% [12]. This lower sensitivity in sterile body fluids can be attributed to the low number of organisms, poor lysis of bacteria and interference by proteinaceous compounds in the DNA extraction step. Moreover, among the various sterile body fluids, the vitreous fluid

Author's contribution

Concept of study – KS, AS, AG; Plan of study KS, AG, VG, RS; Collection of data KS, AG, VG, RS, KA, RB, SP; Analysis of results KS, AG, RS, MS; Drafting of manuscript KS, MS, AS, PF; Study supervision AG.

Conflict of interest

None.

Acknowledgement

We acknowledge the financial support provided by DBT.

References (19)

There are more references available in the full text version of this article.

Cited by (15)

  • Detection of viable Mycobacterium tuberculosis in ocular fluids using mRNA-based multiplex polymerase chain reaction

    2022, Indian Journal of Medical Microbiology
    Citation Excerpt :

    The findings of DNA-based MPCR are similar to prior studies wherein IOTB was detected in 77.7% of cases [9]. Our findings, however, vary from earlier reported sensitivity of 22.3% in diagnosing IOTB using GX [12]. Prospective studies with large number of subjects are required to validate these findings.

  • Whitcup and Nussenblatt’s Uveitis: Fundamentals and Clinical Practice

    2021, Whitcup and Nussenblatt's Uveitis: Fundamentals and Clinical Practice
  • Comparative evaluation of Xpert MTB/RIF assay with multiplex polymerase chain reaction for the diagnosis of tuberculous meningitis

    2018, Tuberculosis
    Citation Excerpt :

    Though the labor cost and laboratory labor time of MPCR is USD3-4 and 4–5 h, respectively and that of GXpert is USD15 and 40 min, respectively, the running cost of MPCR which is about one-tenth of GXpert could compensate for establishing the necessary laboratory infrastructure needed to reliably carry out MPCR. GXpert had one false-positive for detecting rifampicin resistance, an issue well-documented in prior studies also [31,32]. These findings highlight the need for molecular confirmation of all cases reported as rifampicin-resistant by GXpert by sequencing the gene fragment and detecting mutations in individual codons.

  • Laboratory investigations in uveitis: current practice and future directions

    2018, Canadian Journal of Ophthalmology
    Citation Excerpt :

    Xpert MTB/RIF is an automated, cartridge-based nucleic amplification assay that can detect M. tuberculosis as well as rifampicin resistance–conferring mutations. High sensitivities and specificities with this technique from vitreous samples have been reported in the literature.33–35 Recently, the MTBDRplus line probe assay has promised its diagnostic potential to screen for intraocular tuberculosis and simultaneous detection of rifampicin and isoniazid resistance in the vitreous fluid.36

  • Ophthalmic manifestations of tuberculosis

    2023, Current Opinion in Ophthalmology
View all citing articles on Scopus
View full text