Occupational screening for tuberculosis and the use of a borderline zone for interpretation of the IGRA in German healthcare workers

PLoS One. 2014 Dec 26;9(12):e115322. doi: 10.1371/journal.pone.0115322. eCollection 2014.

Abstract

Introduction: Healthcare workers (HCWs) in low incidence countries with contact to patients with tuberculosis (TB) are considered a high-risk group for latent TB infection (LTBI) and therefore are routinely screened for LTBI. The German Occupational TB Network data is analyzed in order to estimate the prevalence and incidence of LTBI and to evaluate putative risk factors for a positive IGRA and the performance of IGRA in serial testing.

Methods: 3,823 HCWs were screened with the Quantiferon Gold in Tube (QFT) at least once; a second QFT was performed on 817 HCWs either in the course of contact tracing or serial examination. Risk factors for a positive QFT were assessed by a questionnaire.

Results: We observed a prevalence of LTBI of 8.3%. Putative risk factors for a positive QFT result were age >55 years (OR 6.89), foreign country of birth(OR 2.39), personal history of TB (OR 6.25) and workplace, e.g. infection ward (OR 1.76) or geriatric care (OR 1.99). Of those repeatedly tested, 88.2% (721/817) tested consistently QFT negative and 47 were consistently QFT-positive (5.8%). A conversion was observed in 2.8%(n = 21 of 742 with a negative first QFT) and a reversion occurred in 37.3% (n = 28 of 75 with a positive first QFT). Defining a conversion as an increase of the specific interferon concentration from <0.2 to >0.7 IU/ml, the conversion rate decreased to 1.2% (n = 8). Analogous to this, the reversion rate decreased to 18.8% (n = 9) [corrected].

Discussion: In countries with a low incidence of TB and high hygiene standards, the LTBI infection risk for HCWs seems low. Introducing a borderline zone from 0.2 to ≤ 0.7 IU/ml may help to avoid unnecessary X-rays and preventive chemotherapy. No case of active TB was detected. Therefore, it might be reasonable to further restrict TB screening to HCWs who had unprotected contact with infectious patients or materials.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Germany
  • Health Personnel
  • Humans
  • Latent Tuberculosis / diagnosis*
  • Latent Tuberculosis / epidemiology*
  • Male
  • Mass Screening
  • Middle Aged
  • Prevalence
  • Risk Factors
  • Surveys and Questionnaires
  • Tuberculin Test

Grant support

No special funds were received for this study. However, the Institute for Health Services Research in Dermatology and Nursing of the University Medical Centre Hamburg-Eppendorf (UKE) receives an unrestricted fund from the Institution for Statutory Accident Insurance and Prevention in the Health and Welfare services (BGW) on an annual basis to maintain the working group at the UKE. The funds are provided by a non-profit organization that is part of the social security system in Germany. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.