Pooling sputum from multiple individuals for Xpert® MTB/RIF testing: A strategy for screening high-risk populations

V. Zishiri, V. Chihota, K. McCarthy, S. Charalambous, G. J. Churchyard, C. J. Hoffmann

Research output: Contribution to journalArticle

Abstract

SETTING: Symptom-based screening for tuberculosis (TB) disease is limited by poor performance of symptom screening in several key populations. We tested the hypothesis that pooling sputum from multiple individuals for Xpert® MTB/RIF testing would reduce the number of tests required while retaining an acceptable sensitivity, thus allowing the use of Xpert for TB screening.

METHODS: We compared pooling ratios that would require the least number of assays using Xpert and determined that for a population with a TB prevalence of approximately 3%, a 1:5 pooling ratio is optimal. To evaluate sensitivity, we generated pools of one specimen with known Mycobacterium tuberculosis culture positivity (smear microscopy-positive or -negative) with four culture-negative specimens.

RESULTS: All 20 of the pools generated from a smearand culture-positive sputum sample were positive using Xpert. Of the 22 pools with a smear-negative, culturepositive sample, we included 17 in the analysis, of which 13 (76%) were Xpert-positive.

CONCLUSIONS: Pooling of sputum samples using Xpert achieved reasonable sensitivity and warrants further evaluation of the systematic screening of high TB prevalence populations.

Original languageEnglish (US)
Pages (from-to)87-90
Number of pages4
JournalInternational Journal of Tuberculosis and Lung Disease
Volume19
Issue number1
DOIs
StatePublished - Jan 1 2015

Keywords

  • Africa
  • Case finding
  • Genexpert
  • Nucleic acid amplification
  • Pooling
  • TB

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Infectious Diseases

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