Factors associated with positive Mantoux results in NHS healthcare workers

The Mantoux method of tuberculin skin testing has been used in tuberculosis (TB) screening of healthcare workers (HCWs) in the UK National Health Service (NHS) for many years. More recently, there have been problems with the supply of the Mantoux test solution presenting a challenge to its continued use.

To review results of Mantoux testing and determine factors associated with positive Mantoux result, i.e. tuberculin reactivity, in NHS HCWs, with a view to streamlining the TB screening process.

A retrospective descriptive study. We extracted data on HCW demographics, country of birth, previous stay or work in a high TB prevalence country, TB contact, Bacillus Calmette-Guérin (BCG) vaccination, previous tuberculin skin test (TST) and Mantoux results from the occupational health records of HCWs who had a Mantoux test during 1 January 2007 to 31 December 2010 inclusive.

We reviewed the records of 246 HCWs. Overall, 46% were Mantoux positive (defined as ≥6 mm skin induration). Factors associated with positive Mantoux result were BCG vaccination [odds ratio (OR) 2.30; 95% confidence interval (CI) 1.14-4.66]; stay or work in a high TB prevalence country (OR 7.52; CI 2.76-20.46) and previous TST (OR 2.78; CI 1.25-6.19).

BCG vaccination, stay or work in a high TB prevalence country and previous TST were associated with positive Mantoux results. These factors could be used to predict Mantoux results, with the potential of substituting Mantoux testing.