Factors associated with positive Mantoux results in NHS healthcare workers

Factors associated with positive Mantoux results in NHS healthcare workers Abstract Background 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. Aims 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. Methods 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. Results 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). Conclusions 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. BCG vaccination, healthcare worker, Mantoux test, NHS, tuberculin skin test, tuberculosis (TB) screening Introduction The Department of Health (DH) recommends tuberculosis (TB) screening of new healthcare workers (HCWs) including Mantoux tuberculin skin testing [1]. The National Institute for Health and Care Excellence (NICE) recommends Mantoux testing in the screening of new UK National Health Service (NHS) employees followed by an interferon gamma release assay in specified circumstances if Mantoux positive [2]. However, there have been problems with the supply of the purified protein derivative solution used for the Mantoux test [3]. Furthermore, there are logistical challenges inherent in administering the Mantoux test including the requirement for the HCW to attend on at least two occasions as well as the need to maintain operator training and skill in injecting the solution and in reading the results [4]. Against this background, we sought to explore whether Mantoux testing could be substituted by identifying factors associated with positive results, i.e. with tuberculin reactivity. Methods A retrospective descriptive study was conducted using the occupational health (OH) records of HCWs in a UK NHS hospital. Those who had Mantoux tests over a 4-year period, 1 January 2007 to 31 December 2010, were identified from the OH database. Those who did not attend for the reading of their skin induration to obtain a Mantoux result were excluded. Information was extracted into a bespoke data extraction form including HCWs’ demographics, their exposure to putative TB risk factors, Bacillus Calmette–Guérin (BCG) vaccination history, prior tuberculin skin test (TST) and the Mantoux result. SPSS v. 16 was used for statistical analyses. The association between HCWs’ characteristics and positive Mantoux result was investigated by the chi-squared test or the Fisher’s exact test. Univariate and multivariate regression analyses were performed. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to indicate the magnitude of the association. Statistical significance was P ≤0.05. Ethical approval was granted by the Oxfordshire Research Ethics Committee (REC) B (11/SC/0005). Results Of the 275 HCWs identified from the database who had Mantoux tests, three records were not traceable; four had been transferred to another provider and 22 did not attend for reading of results, therefore, 246 HCWs were included in the study. HCWs’ characteristics are presented in Table 1. Age range was 16–60 years. Fifty-five HCWs (22%) were born outside the UK: 37 (15%) in Africa, six (2%) in Europe, seven (3%) in Asia and two (1%) in North America. Table 1. Characteristics of the HCWs; n = 246 Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) aOf the 55 born outside the UK, 43 were born in high TB prevalence countries. View Large Table 1. Characteristics of the HCWs; n = 246 Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) aOf the 55 born outside the UK, 43 were born in high TB prevalence countries. View Large An induration of ≥6 mm was considered positive and 46% had a positive result. From univariate analyses, non-UK birth, birth in a country of high TB prevalence, stay/work in a high TB prevalence country, previous work in healthcare, BCG vaccination and previous TST were significantly associated with positive Mantoux result (P ≤ 0.05). The other factors did not show a significant association (Table 2). From multivariate regression analysis, the factors that remained independently associated with tuberculin reactivity were BCG vaccination, OR 2.30, 95% CI 1.14–4.66 (P < 0.05); stay/work in a country of high TB prevalence, OR 7.52, 95% CI 2.76–20.46 (P < 0.001); and previous TST, OR 2.78, 95% CI 1.25–6.19 (P < 0.05). Table 2. Factors associated with positive Mantoux results (univariate analysis) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) View Large Table 2. Factors associated with positive Mantoux results (univariate analysis) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) View Large Discussion We found that the factors independently associated with positive Mantoux results, i.e. tuberculin reactivity, in this cohort of NHS workers were BCG vaccination, previous TST and stay/work in a high TB prevalence country. The study cohort was representative of the gender and ethnic distribution of the NHS workforce [5]. In this study, 46% had positive Mantoux results. This is higher than other studies of HCWs in some low TB prevalence countries [6,7] but similar to a study of Canadian physicians [8]. The latter study [8] attributed a large proportion of the Mantoux reactivity to BCG vaccination and foreign birth. A study found Mantoux reactivity of only 6% [6] but all the study participants were born locally. Of note, these studies [6–8] defined a positive result as ≥10 mm skin induration compared with ≥6 mm in our study. Consistent with our findings, BCG vaccination was associated with Mantoux reactivity in other studies [7,8]. We found a significant association between stay/work in a high TB prevalence country and tuberculin reactivity. Similarly, a previous study found that practising medicine in a medium to high TB burden country was associated with Mantoux reactivity [8]. There was association between foreign birth and positive Mantoux in some studies [7,8], but our study did not demonstrate this association likely due to the strong correlation between non-UK birth and stay/work in a high TB prevalence country in our study population. We found a significant association between previous TST and positive Mantoux. This association was independent of the result of the previous TST and has been identified in other studies [9,10]. This study did not find an association between Mantoux results and gender in keeping with other studies [7,8]. We examined the relationship between positive Mantoux and previous work in healthcare but this was not significant. It is worth noting that we could not ascertain the duration of previous employment in healthcare from the HCWs’ records. Studies that examined the relationship between years of employment in healthcare and TST reactivity found that increasing years of employment in healthcare is associated with TST reactivity [6,10]. We did not find a significant association with previous TB contact. This is likely due to the small number of HCWs with this exposure in our study. Household, but not occupational TB contact, was found to be significantly associated with Mantoux reactivity in a study of Italian HCWs [6]. Limitations of our study include its small size and retrospective design based on available records only. Furthermore, there were small numbers in some categories which may have prevented some associations from becoming fully apparent in the analyses. A prospective design including a larger population may address some of these limitations. The study identified factors that are significantly associated with positive Mantoux results. We propose that these factors be used in predicting the Mantoux status of HCWs where this information is required as part of their TB screening. Key points Factors that were associated with positive Mantoux results in a cohort of National Health Service healthcare workers were Bacillus Calmette–Guérin vaccination, previous tuberculin skin test and stay/work in high tuberculosis prevalence country. Using these factors during tuberculosis screening can add to the evidence base when assessing the need for Mantoux testing. These factors can be used to predict tuberculin reactivity and help to streamline the tuberculosis screening process in healthcare workers. Competing interests None declared. Acknowledgements This paper derives from the MSc thesis completed by the lead author. We would like to thank Dr David Baxter, Lecturer in Public Health Medicine, University of Manchester (MSc thesis adviser); staff of the Staff Health & Wellbeing Department Milton Keynes University Hospital NHS Foundation Trust and the organizers of the Society of Occupational Medicine’s Authors’ Workshop 2013. References 1. Department of Health . Health Clearance for Tuberculosis, Hepatitis B, Hepatitis C and HIV: New Healthcare Workers . 2007 . https://www.gov.uk/government/uploads/system/uploads/attachment data/file/382152/health_clearance_tuberculosis_hepatitis_hiv.pdf (20 January 2018, date last accessed) . 2. NICE . Tuberculosis Clinical Diagnosis and Management of Tuberculosis, and Measures for Its Prevention and Control .  2011 . http://guidance.nice.org.uk/nicemedia/live/13422/53642/53642.pdf ( 13 September 2016 , date last accessed). 3. Public Health England . Vaccine Update. 2015 March 2015(226) .  https://www.gov.uk/government/uploads/ system/uploads/attachment_data/file/409767/PHE_9254_VU_226_Mar2015_special_08.pdf (20 January 2018, date last accessed) . 4. Menzies D , Pai M , Comstock G . Meta-analysis: new tests for the diagnosis of latent tuberculosis infection: areas of uncertainty and recommendations for research . Ann Int Med 2007 ; 146 : 340 – 354 . Google Scholar CrossRef Search ADS PubMed 5. NHS Employers . Ethnicity in the NHS Infographic . 2016 . http://www.nhsemployers.org/~/media/Employers/Publications/Ethnicity%20in%20the%20NHS.PDF ( 13 September 2016 , date last accessed). PubMed PubMed 6. Franchi A , Diana O , Franco G . Job-related risk of latent tuberculosis infection in a homogeneous population of hospital workers in a low incidence area . Am J Ind Med 2009 ; 52 : 297 – 303 . Google Scholar CrossRef Search ADS PubMed 7. Warren DK , Foley KM , Polish LB , Seiler SM , Fraser VJ . Tuberculin skin testing of physicians at a Midwestern teaching hospital: a 6-year prospective study . Clin Infect Dis 2001 ; 32 : 1331 – 1337 . Google Scholar CrossRef Search ADS PubMed 8. Plitt SS , Soskolne CL , Fanning EA , Newman SC . Prevalence and determinants of tuberculin reactivity among physicians in Edmonton, Canada: 1996–1997 . Int J Epidemiol 2001 ; 30 : 1022 – 1028 . Google Scholar CrossRef Search ADS PubMed 9. Barsegian V , Mathias KD , Wrighton-Smith P , Grosse-Wilde H , Lindemann M . Prevalence of latent tuberculosis infection in German radiologists . J Hosp Infect 2008 ; 69 : 69 – 76 . Google Scholar CrossRef Search ADS PubMed 10. Tan L-H , Kamarulzaman A , Liam C-K , Lee T-C . Tuberculin skin testing among healthcare workers in the University of Malaya Medical Centre, Kuala Lumpur, Malaysia . Infect Control Hosp Epidemiol 2002 ; 23 : 584 – 590 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Occupational Medicine Oxford University Press

Factors associated with positive Mantoux results in NHS healthcare workers

Occupational Medicine , Volume Advance Article (4) – Mar 20, 2018

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Abstract

Abstract Background 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. Aims 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. Methods 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. Results 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). Conclusions 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. BCG vaccination, healthcare worker, Mantoux test, NHS, tuberculin skin test, tuberculosis (TB) screening Introduction The Department of Health (DH) recommends tuberculosis (TB) screening of new healthcare workers (HCWs) including Mantoux tuberculin skin testing [1]. The National Institute for Health and Care Excellence (NICE) recommends Mantoux testing in the screening of new UK National Health Service (NHS) employees followed by an interferon gamma release assay in specified circumstances if Mantoux positive [2]. However, there have been problems with the supply of the purified protein derivative solution used for the Mantoux test [3]. Furthermore, there are logistical challenges inherent in administering the Mantoux test including the requirement for the HCW to attend on at least two occasions as well as the need to maintain operator training and skill in injecting the solution and in reading the results [4]. Against this background, we sought to explore whether Mantoux testing could be substituted by identifying factors associated with positive results, i.e. with tuberculin reactivity. Methods A retrospective descriptive study was conducted using the occupational health (OH) records of HCWs in a UK NHS hospital. Those who had Mantoux tests over a 4-year period, 1 January 2007 to 31 December 2010, were identified from the OH database. Those who did not attend for the reading of their skin induration to obtain a Mantoux result were excluded. Information was extracted into a bespoke data extraction form including HCWs’ demographics, their exposure to putative TB risk factors, Bacillus Calmette–Guérin (BCG) vaccination history, prior tuberculin skin test (TST) and the Mantoux result. SPSS v. 16 was used for statistical analyses. The association between HCWs’ characteristics and positive Mantoux result was investigated by the chi-squared test or the Fisher’s exact test. Univariate and multivariate regression analyses were performed. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to indicate the magnitude of the association. Statistical significance was P ≤0.05. Ethical approval was granted by the Oxfordshire Research Ethics Committee (REC) B (11/SC/0005). Results Of the 275 HCWs identified from the database who had Mantoux tests, three records were not traceable; four had been transferred to another provider and 22 did not attend for reading of results, therefore, 246 HCWs were included in the study. HCWs’ characteristics are presented in Table 1. Age range was 16–60 years. Fifty-five HCWs (22%) were born outside the UK: 37 (15%) in Africa, six (2%) in Europe, seven (3%) in Asia and two (1%) in North America. Table 1. Characteristics of the HCWs; n = 246 Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) aOf the 55 born outside the UK, 43 were born in high TB prevalence countries. View Large Table 1. Characteristics of the HCWs; n = 246 Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) Mean age (SD) years 35 (11.2) Gender, no. (%)  Female 213 (87)  Male 33 (13) Tuberculin reactivity, no. (%)  Induration ≥6 mm 112 (46)  Induration <6 mm 134 (54) BCG vaccination, no. (%)  Yes 135 (55)  No 85 (34)  Not known 26 (11) Country of birth, no. (%)  UK 191 (78)  Non-UK 55a (22) Stay/work in high TB prevalence countries, no. (%)  Yes 53 (22)  No 192 (77)  Not known 1 (1) Close contact with TB patients, no. (%)  Yes 13 (5)  No 233 (95) Post, no. (%)  Clinical 203 (82)  Non-clinical 43 (18) History of chronic medical condition, no. (%)  Yes 39 (16)  No 207 (84) aOf the 55 born outside the UK, 43 were born in high TB prevalence countries. View Large An induration of ≥6 mm was considered positive and 46% had a positive result. From univariate analyses, non-UK birth, birth in a country of high TB prevalence, stay/work in a high TB prevalence country, previous work in healthcare, BCG vaccination and previous TST were significantly associated with positive Mantoux result (P ≤ 0.05). The other factors did not show a significant association (Table 2). From multivariate regression analysis, the factors that remained independently associated with tuberculin reactivity were BCG vaccination, OR 2.30, 95% CI 1.14–4.66 (P < 0.05); stay/work in a country of high TB prevalence, OR 7.52, 95% CI 2.76–20.46 (P < 0.001); and previous TST, OR 2.78, 95% CI 1.25–6.19 (P < 0.05). Table 2. Factors associated with positive Mantoux results (univariate analysis) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) View Large Table 2. Factors associated with positive Mantoux results (univariate analysis) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) Characteristic Total Mantoux positive, n (%) OR (95% CI) P value BCG vaccination  Yes 135 78 (58) 3.69 (2.05–6.64) <0.001  No 85 23 (27) Stay/work in high TB prevalence country  Yes 53 37(70) 3.61 (1.88–6.94) <0.001  No 192 75 (39) Previous TST  Yes 137 71 (52) 1.84 (1.07–3.15) <0.05  No 92 34 (37) Country of birth  UK 191 80 (42) 1.93 (1.05–3.55) <0.05  Non-UK 55 32 (58) Birth country of high TB prevalence  Yes 43 30 (70) 3.41 (1.68–6.92) <0.01  No 203 82 (40) Previous work in healthcare  Yes 139 74 (53) 1.99 (1.18–3.38) <0.05  No 99 36 (36) View Large Discussion We found that the factors independently associated with positive Mantoux results, i.e. tuberculin reactivity, in this cohort of NHS workers were BCG vaccination, previous TST and stay/work in a high TB prevalence country. The study cohort was representative of the gender and ethnic distribution of the NHS workforce [5]. In this study, 46% had positive Mantoux results. This is higher than other studies of HCWs in some low TB prevalence countries [6,7] but similar to a study of Canadian physicians [8]. The latter study [8] attributed a large proportion of the Mantoux reactivity to BCG vaccination and foreign birth. A study found Mantoux reactivity of only 6% [6] but all the study participants were born locally. Of note, these studies [6–8] defined a positive result as ≥10 mm skin induration compared with ≥6 mm in our study. Consistent with our findings, BCG vaccination was associated with Mantoux reactivity in other studies [7,8]. We found a significant association between stay/work in a high TB prevalence country and tuberculin reactivity. Similarly, a previous study found that practising medicine in a medium to high TB burden country was associated with Mantoux reactivity [8]. There was association between foreign birth and positive Mantoux in some studies [7,8], but our study did not demonstrate this association likely due to the strong correlation between non-UK birth and stay/work in a high TB prevalence country in our study population. We found a significant association between previous TST and positive Mantoux. This association was independent of the result of the previous TST and has been identified in other studies [9,10]. This study did not find an association between Mantoux results and gender in keeping with other studies [7,8]. We examined the relationship between positive Mantoux and previous work in healthcare but this was not significant. It is worth noting that we could not ascertain the duration of previous employment in healthcare from the HCWs’ records. Studies that examined the relationship between years of employment in healthcare and TST reactivity found that increasing years of employment in healthcare is associated with TST reactivity [6,10]. We did not find a significant association with previous TB contact. This is likely due to the small number of HCWs with this exposure in our study. Household, but not occupational TB contact, was found to be significantly associated with Mantoux reactivity in a study of Italian HCWs [6]. Limitations of our study include its small size and retrospective design based on available records only. Furthermore, there were small numbers in some categories which may have prevented some associations from becoming fully apparent in the analyses. A prospective design including a larger population may address some of these limitations. The study identified factors that are significantly associated with positive Mantoux results. We propose that these factors be used in predicting the Mantoux status of HCWs where this information is required as part of their TB screening. Key points Factors that were associated with positive Mantoux results in a cohort of National Health Service healthcare workers were Bacillus Calmette–Guérin vaccination, previous tuberculin skin test and stay/work in high tuberculosis prevalence country. Using these factors during tuberculosis screening can add to the evidence base when assessing the need for Mantoux testing. These factors can be used to predict tuberculin reactivity and help to streamline the tuberculosis screening process in healthcare workers. Competing interests None declared. Acknowledgements This paper derives from the MSc thesis completed by the lead author. We would like to thank Dr David Baxter, Lecturer in Public Health Medicine, University of Manchester (MSc thesis adviser); staff of the Staff Health & Wellbeing Department Milton Keynes University Hospital NHS Foundation Trust and the organizers of the Society of Occupational Medicine’s Authors’ Workshop 2013. References 1. Department of Health . Health Clearance for Tuberculosis, Hepatitis B, Hepatitis C and HIV: New Healthcare Workers . 2007 . https://www.gov.uk/government/uploads/system/uploads/attachment data/file/382152/health_clearance_tuberculosis_hepatitis_hiv.pdf (20 January 2018, date last accessed) . 2. NICE . Tuberculosis Clinical Diagnosis and Management of Tuberculosis, and Measures for Its Prevention and Control .  2011 . http://guidance.nice.org.uk/nicemedia/live/13422/53642/53642.pdf ( 13 September 2016 , date last accessed). 3. Public Health England . Vaccine Update. 2015 March 2015(226) .  https://www.gov.uk/government/uploads/ system/uploads/attachment_data/file/409767/PHE_9254_VU_226_Mar2015_special_08.pdf (20 January 2018, date last accessed) . 4. Menzies D , Pai M , Comstock G . Meta-analysis: new tests for the diagnosis of latent tuberculosis infection: areas of uncertainty and recommendations for research . Ann Int Med 2007 ; 146 : 340 – 354 . Google Scholar CrossRef Search ADS PubMed 5. NHS Employers . Ethnicity in the NHS Infographic . 2016 . http://www.nhsemployers.org/~/media/Employers/Publications/Ethnicity%20in%20the%20NHS.PDF ( 13 September 2016 , date last accessed). PubMed PubMed 6. Franchi A , Diana O , Franco G . Job-related risk of latent tuberculosis infection in a homogeneous population of hospital workers in a low incidence area . Am J Ind Med 2009 ; 52 : 297 – 303 . Google Scholar CrossRef Search ADS PubMed 7. Warren DK , Foley KM , Polish LB , Seiler SM , Fraser VJ . Tuberculin skin testing of physicians at a Midwestern teaching hospital: a 6-year prospective study . Clin Infect Dis 2001 ; 32 : 1331 – 1337 . Google Scholar CrossRef Search ADS PubMed 8. Plitt SS , Soskolne CL , Fanning EA , Newman SC . Prevalence and determinants of tuberculin reactivity among physicians in Edmonton, Canada: 1996–1997 . Int J Epidemiol 2001 ; 30 : 1022 – 1028 . Google Scholar CrossRef Search ADS PubMed 9. Barsegian V , Mathias KD , Wrighton-Smith P , Grosse-Wilde H , Lindemann M . Prevalence of latent tuberculosis infection in German radiologists . J Hosp Infect 2008 ; 69 : 69 – 76 . Google Scholar CrossRef Search ADS PubMed 10. Tan L-H , Kamarulzaman A , Liam C-K , Lee T-C . Tuberculin skin testing among healthcare workers in the University of Malaya Medical Centre, Kuala Lumpur, Malaysia . Infect Control Hosp Epidemiol 2002 ; 23 : 584 – 590 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Occupational MedicineOxford University Press

Published: Mar 20, 2018

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