Laboratory cross-contamination of Mycobacterium tuberculosis: a systematic review and meta-analysis

Research output: Contribution to journalArticle

  • External authors:
  • Aleksandra Barac
  • Hannah Karimzadeh-Esfahani
  • Mahya Pourostadi
  • Mohammad Taghi Rahimi
  • Ehsan Ahmadpour
  • Jalil Rashedi
  • Behroz Mahdavipoor
  • Hossein Samadi Kafil
  • Adel Spotin
  • Kalkidan Hassen Abate
  • Mohammad Asgharzadeh


Background: Microbiological cultures are the mainstay of the diagnosis of tuberculosis (TB). False positive TB results lead to significant unnecessary therapeutic and economic burden and are frequently caused by laboratory cross-contamination. The aim of this meta-analysis was to quantify the prevalence of laboratory cross-contamination.
Methods: Through a systematic review of five electronic databases, we identified studies reporting rates of laboratory cross-contamination, confirmed by molecular techniques in TB cultures. We evaluated the quality of the identified studies using the National Institute of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies, and conducted a meta-analysis using standard methodology recommended by the Cochrane Collaboration.
Results: Based on 31 eligible studies evaluating 29,839 TB cultures, we found that 2% (95% confidence intervals [CI]: 1-2%) of all positive TB cultures represent false positive results secondary to laboratory cross-contamination. More importantly, we evaluated the rate of laboratory cross-contamination in cases where a single positive TB culture was available in addition to at least one negative TB culture, and we found a rate of 15% (95%CI: 6-33%). Moreover, 9.2% (91/990) of all patients with a preliminary diagnosis of TB had false-positive results and received unnecessary and potentially harmful treatments.
Conclusions: Our results highlight a remarkably high prevalence of false positive TB results as a result of laboratory cross-contamination, especially in single-positive TB cultures, leading to the administration of unnecessary, harmful treatments. The need for the adoption of strict technical standards for mycobacterial cultures cannot be overstated.

Bibliographical metadata

Original languageEnglish
Publication statusAccepted/In press - 23 May 2019