Background & Objective: Identification and treatment of latent-tuberculosis-infection (LTBI) has remained at backstage for long. This study looks at the effect of graded-increase in clinical exposure on incidence of LTBI in health-care students and their non-exposed peers.

Methods: It was a cross-sectional observational study including 817 students (medical and non-medical). A one-step tuberculin-skin-test (TST) was performed using Monteux-technique. A positive TST, induration of ≥10 mm, was considered suggestive of LTBI. Prevalence of LTBI was recorded among students of successive years and comparisons were made, in the two groups, with demographic variables.

Results: Mean age of the study population was 20.83±1.86 years. 73.19% students were from an urban-background and 67.68% were from high-income-group. In medical and nursing group 29.08% and 30.55% students had TST positivity as compared to 14.23% in engineering students. Over four-years, the percentage of medical and nursing students having positive-TST increased from 13% to ≥40% (p<0.05), but no such change was present among engineering students. Relative-risk of acquiring LTBI in medical profession was ≥2.1 as compared to non-medical profession. There was a strong correlation of TST-positivity with increasing clinical exposure in the form of medical/surgical postings even after excluding TST-positivity due to community exposure (p<0.01). There was no association of TST positivity with gender, residence, family income, parents education and occupation and BCG vaccination (p>0.05).

Conclusion:  In our study, a higher prevalence of latent tuberculosis infection was demonstrated among medical and nursing students as compared to engineering students. This data favours further studies on the role of heightened infection control practices and potential role of treating LTBI among healthcare-workers.

Keywords: Healthcare workers, Latent-tuberculosis-infection, Medical-students, Monteux-test, tuberculin skin test

1. World Health O. Global tuberculosis report 2015. 20th ed ed. Geneva: World Health Organization; 2015 2015.
2. Joshi R, Reingold AL, Menzies D, Pai M. Tuberculosis among health-care workers in low- and middle-income countries: a systematic review. PLoS Med. 2006;3(12): e494.
3. Pai M, Gokhale K, Joshi R, Dogra S, Kalantri S, Mendiratta DK, et al. Mycobacterium tuberculosis infection in health care workers in rural India: comparison of a whole-blood interferon gamma assay with tuberculin skin testing. Jama. 2005;293(22):2746-55.
4. Christopher DJ, Daley P, Armstrong L, James P, Gupta R, Premkumar B, et al. Tuberculosis infection among young nursing trainees in South India. PLoS One. 2010;5(4):e10408.
5. Agarwal U, Mathur D, Mathur D, Besarwal R, Agarwal P. Ear sign. Lung India. 2005;22(4):105-6.
6. Pai M, Christopher DJ. Protecting young healthcare trainees from tuberculosis: can we overcome apathy? Natl Med J India. 2011;24(4):198-200.
7. Ben Amor Y, Nemser B, Singh A, Sankin A, Schluger N. Underreported threat of multidrug-resistant tuberculosis in Africa. Emerg Infect Dis. 2008;14(9):1345-52.
8. Blumberg HM, Watkins DL, Berschling JD, Antle A, Moore P, White N, et al. Preventing the nosocomial transmission of tuberculosis. Ann Intern Med. 1995;122(9):658-63.
9. Jelip J, Mathew GG, Yusin T, Dony JF, Singh N, Ashaari M, et al. Risk factors of tuberculosis among health care workers in Sabah, Malaysia. Tuberculosis (Edinb). 2004;84(1-2):19-23.
10. Torres Costa J, Silva R, Sá R, Cardoso MJ, Nienhaus A. Results of five-year systematic screening for latent tuberculosis infection in healthcare workers in Portugal. Journal of Occupational Medicine and Toxicology. 2010;5(1):22.
11. Getahun H, Matteelli A, Abubakar I, Aziz MA, Baddeley A, Barreira D, et al. Management of latent Mycobacterium tuberculosis infection: WHO guidelines for low tuberculosis burden countries. Eur Respir J. 2015;46(6):1563-76.
12. Singla N, Sharma PP, Jain RC. Awareness about tuberculosis among nurses working in a tuberculosis hospital and in a general hospital in Delhi, India. Int J Tuberc Lung Dis. 1998;2(12):1005-10.
13. Demkow U, Broniarek-Samson B, Filewska M, Lewandowska K, Maciejewski J, Zycinska K, et al. Prevalence of latent tuberculosis infection in health care workers in Poland assessed by interferon-gamma whole blood and tuberculin skin tests. J Physiol Pharmacol. 2008;59 Suppl 6:209-17.
14. Stuart RL, Bennett N, Forbes A, Grayson ML. A paired comparison of tuberculin skin test results in health care workers using 5 TU and 10 TU tuberculin. Thorax. 2000;55(8):693-5.
15. Behnaz F, Mohammadzadeh M, Mohammadzade G. Tuberculin skin tests among medical students at risk for nosocomial transmission of Mycobacterium tuberculosis in Yazd, Iran. International Journal of Infection Control. 2013;9.
16. Durando P, Sotgiu G, Spigno F, Piccinini M, Mazzarello G, Viscoli C, et al. Latent tuberculosis infection and associated risk factors among undergraduate healthcare students in Italy: a cross-sectional study. BMC Infectious Diseases. 2013;13(1):443.
17. Abbas MA, AlHamdan NA, Fiala LA, AlEnezy AK, AlQahtani MS. Prevalence of latent TB among health care workers in four major tertiary care hospitals in Riyadh, Saudi Arabia. J Egypt Public Health Assoc. 2010;85(1-2):61-71.
18. Kakkar R. Socio‐Demographic Profile of Tuberculosis patient: A hospital based study at Dehradun. National Journal of Community Medicine. 2014;5:6-9.
19. Pelly TF, Santillan CF, Gilman RH, Cabrera LZ, Garcia E, Vidal C, et al. Tuberculosis skin testing, anergy and protein malnutrition in Peru. Int J Tuberc Lung Dis. 2005;9(9):977-84.
20. Dias MHdP, Hayashi A. Prova tuberculínica, BCG oral e infecção tuberculosa em crianças menores de 5 anos. Revista de Saúde Pública. 1978;12:443-54.
21. Chadha VK, Jagannatha PS, Kumar P. Can BCG-vaccinated children be included in tuberculin surveys to estimate the annual risk of tuberculous infection in India? Int J Tuberc Lung Dis. 2004;8(12):1437-42.
22. Teixeira EG, Menzies D, Comstock GW, Cunha AJ, Kritski AL, Soares LC, et al. Latent tuberculosis infection among undergraduate medical students in Rio de Janeiro State, Brazil. Int J Tuberc Lung Dis. 2005;9(8):841-7.
23. Mugerwa H, Byarugaba DK, Mpooya S, Miremba P, Kalyango JN, Karamagi C, et al. High Prevalence of tuberculosis infection among medical students in Makerere University, Kampala: results of a cross sectional study. Archives of Public Health. 2013;71(1):7.
24. Silva VM, Cunha AJ, Oliveira JR, Figueira MM, Nunes ZB, DeRiemer K, et al. Medical students at risk of nosocomial transmission of Mycobacterium tuberculosis. Int J Tuberc Lung Dis. 2000;4(5):420-6.
25. Christopher DJ, James P, Daley P, Armstrong L, Isaac BT, Thangakunam B, et al. High annual risk of tuberculosis infection among nursing students in South India: a cohort study. PLoS One. 2011;6(10):e26199.
26. Pérez-Lu JE, Cárcamo CP, García PJ, Bussalleu A, Bernabé-Ortiz A. Tuberculin skin test conversion among health sciences students: a retrospective cohort study. Tuberculosis (Edinb). 2013;93(2):257-62.

Dr Lokesh Kumar Lalwani

Assistant Professor, Department of Tuberculosis & Respiratory Diseases, Post Graduate Institute of Medical Sciences, Rohtak (Haryana), India-124001