Late boosting phenomenon in TST conversion among health care workers

W. H. Farah, L. E. Breeher, R. D. Newcomb, Mohammad H Murad, A. I.S. Vaughn, P. T. Hagen, R. G. Molella

Research output: Contribution to journalArticle

Abstract

Background Available information is insufficient to guide determination of whether tuberculin skin test (TST) conversions of health care workers (HCWs) within 2 years of two-step testing are related to occupational exposures or to other causes, including late boosting. Aims To describe the epidemiologic factors of TST conversion in HCWs, comparing early TST conversion (≤ 2 years after two-step testing) with late conversion to possibly distinguish late boosting phenomenon from occupational TST conversion. Methods Retrospective analysis of a database of TSTs of HCWs from 1 January 1998, through 31 May 2014, in the United States Midwest. Results In total, 40 142 HCWs had 197 932 tests over the 16 years, with 123 conversions (conversion rate: 0.3%; 95% CI 0.3-0.4%). Among 61 HCWs with a negative two-step TST, 30 (49%) were found to have early TST conversion within 2 years; 31 (51%) had late conversion, with likely occupational exposure but no identifiable community risks. Persons with early conversion were more likely to be born outside the USA (89% versus 57%; P < 0.05), had a higher rate of prior bacille Calmette- Guérin (BCG) vaccination (89% versus 52%; P < 0.05) and had no identifiable risk factors for conversion (63% versus 58%; P ≤ 0.05). Conclusions Early conversions among HCWs after negative two-step TST are associated with various nonoccupational factors, including international birth and BCG vaccination history. Therefore, conversion is not a reliable indicator of recent tuberculosis contact in this population, and two-step TST is insufficient to discount a delayed boosting response for HCWs.

Original languageEnglish (US)
Pages (from-to)484-489
Number of pages6
JournalOccupational Medicine
Volume67
Issue number6
DOIs
StatePublished - Aug 1 2017

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Tuberculin Test
Skin Tests
Delivery of Health Care
Occupational Exposure
Vaccination
Epidemiologic Factors
Tuberculosis
History
Parturition
Databases

Keywords

  • Boosting phenomenon
  • Health care workers
  • Latent tuberculosis
  • Skin test

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

Cite this

Farah, W. H., Breeher, L. E., Newcomb, R. D., Murad, M. H., Vaughn, A. I. S., Hagen, P. T., & Molella, R. G. (2017). Late boosting phenomenon in TST conversion among health care workers. Occupational Medicine, 67(6), 484-489. https://doi.org/10.1093/occmed/kqx102

Late boosting phenomenon in TST conversion among health care workers. / Farah, W. H.; Breeher, L. E.; Newcomb, R. D.; Murad, Mohammad H; Vaughn, A. I.S.; Hagen, P. T.; Molella, R. G.

In: Occupational Medicine, Vol. 67, No. 6, 01.08.2017, p. 484-489.

Research output: Contribution to journalArticle

Farah, WH, Breeher, LE, Newcomb, RD, Murad, MH, Vaughn, AIS, Hagen, PT & Molella, RG 2017, 'Late boosting phenomenon in TST conversion among health care workers', Occupational Medicine, vol. 67, no. 6, pp. 484-489. https://doi.org/10.1093/occmed/kqx102
Farah WH, Breeher LE, Newcomb RD, Murad MH, Vaughn AIS, Hagen PT et al. Late boosting phenomenon in TST conversion among health care workers. Occupational Medicine. 2017 Aug 1;67(6):484-489. https://doi.org/10.1093/occmed/kqx102
Farah, W. H. ; Breeher, L. E. ; Newcomb, R. D. ; Murad, Mohammad H ; Vaughn, A. I.S. ; Hagen, P. T. ; Molella, R. G. / Late boosting phenomenon in TST conversion among health care workers. In: Occupational Medicine. 2017 ; Vol. 67, No. 6. pp. 484-489.
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abstract = "Background Available information is insufficient to guide determination of whether tuberculin skin test (TST) conversions of health care workers (HCWs) within 2 years of two-step testing are related to occupational exposures or to other causes, including late boosting. Aims To describe the epidemiologic factors of TST conversion in HCWs, comparing early TST conversion (≤ 2 years after two-step testing) with late conversion to possibly distinguish late boosting phenomenon from occupational TST conversion. Methods Retrospective analysis of a database of TSTs of HCWs from 1 January 1998, through 31 May 2014, in the United States Midwest. Results In total, 40 142 HCWs had 197 932 tests over the 16 years, with 123 conversions (conversion rate: 0.3{\%}; 95{\%} CI 0.3-0.4{\%}). Among 61 HCWs with a negative two-step TST, 30 (49{\%}) were found to have early TST conversion within 2 years; 31 (51{\%}) had late conversion, with likely occupational exposure but no identifiable community risks. Persons with early conversion were more likely to be born outside the USA (89{\%} versus 57{\%}; P < 0.05), had a higher rate of prior bacille Calmette- Gu{\'e}rin (BCG) vaccination (89{\%} versus 52{\%}; P < 0.05) and had no identifiable risk factors for conversion (63{\%} versus 58{\%}; P ≤ 0.05). Conclusions Early conversions among HCWs after negative two-step TST are associated with various nonoccupational factors, including international birth and BCG vaccination history. Therefore, conversion is not a reliable indicator of recent tuberculosis contact in this population, and two-step TST is insufficient to discount a delayed boosting response for HCWs.",
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AU - Newcomb, R. D.

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AU - Vaughn, A. I.S.

AU - Hagen, P. T.

AU - Molella, R. G.

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N2 - Background Available information is insufficient to guide determination of whether tuberculin skin test (TST) conversions of health care workers (HCWs) within 2 years of two-step testing are related to occupational exposures or to other causes, including late boosting. Aims To describe the epidemiologic factors of TST conversion in HCWs, comparing early TST conversion (≤ 2 years after two-step testing) with late conversion to possibly distinguish late boosting phenomenon from occupational TST conversion. Methods Retrospective analysis of a database of TSTs of HCWs from 1 January 1998, through 31 May 2014, in the United States Midwest. Results In total, 40 142 HCWs had 197 932 tests over the 16 years, with 123 conversions (conversion rate: 0.3%; 95% CI 0.3-0.4%). Among 61 HCWs with a negative two-step TST, 30 (49%) were found to have early TST conversion within 2 years; 31 (51%) had late conversion, with likely occupational exposure but no identifiable community risks. Persons with early conversion were more likely to be born outside the USA (89% versus 57%; P < 0.05), had a higher rate of prior bacille Calmette- Guérin (BCG) vaccination (89% versus 52%; P < 0.05) and had no identifiable risk factors for conversion (63% versus 58%; P ≤ 0.05). Conclusions Early conversions among HCWs after negative two-step TST are associated with various nonoccupational factors, including international birth and BCG vaccination history. Therefore, conversion is not a reliable indicator of recent tuberculosis contact in this population, and two-step TST is insufficient to discount a delayed boosting response for HCWs.

AB - Background Available information is insufficient to guide determination of whether tuberculin skin test (TST) conversions of health care workers (HCWs) within 2 years of two-step testing are related to occupational exposures or to other causes, including late boosting. Aims To describe the epidemiologic factors of TST conversion in HCWs, comparing early TST conversion (≤ 2 years after two-step testing) with late conversion to possibly distinguish late boosting phenomenon from occupational TST conversion. Methods Retrospective analysis of a database of TSTs of HCWs from 1 January 1998, through 31 May 2014, in the United States Midwest. Results In total, 40 142 HCWs had 197 932 tests over the 16 years, with 123 conversions (conversion rate: 0.3%; 95% CI 0.3-0.4%). Among 61 HCWs with a negative two-step TST, 30 (49%) were found to have early TST conversion within 2 years; 31 (51%) had late conversion, with likely occupational exposure but no identifiable community risks. Persons with early conversion were more likely to be born outside the USA (89% versus 57%; P < 0.05), had a higher rate of prior bacille Calmette- Guérin (BCG) vaccination (89% versus 52%; P < 0.05) and had no identifiable risk factors for conversion (63% versus 58%; P ≤ 0.05). Conclusions Early conversions among HCWs after negative two-step TST are associated with various nonoccupational factors, including international birth and BCG vaccination history. Therefore, conversion is not a reliable indicator of recent tuberculosis contact in this population, and two-step TST is insufficient to discount a delayed boosting response for HCWs.

KW - Boosting phenomenon

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KW - Latent tuberculosis

KW - Skin test

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