Measuring the risk of contracting latent tuberculosis in clinical training

On average 1 in 10 health science students at King Abdulaziz University Hospital develop an asymptomatic and non-contagious form of tuberculosis known as latent tuberculosis infection (LTBI) during their clinical training.

Tuberculosis (TB) is a public health concern in the Kingdom of Saudi Arabia, where approximately 10 in 100,000 people got the disease in 2018, according to the World Health Organization. A larger proportion of the population, around 9%, is estimated to harbour an inactive form of the TB bacterium Mycobacterium tuberculosis. The dormant bacteria can reactivate after a period of years if the immune system is weakened immune or if other risk factors are present.

Healthcare workers and medical students are at risk of acquiring TB in its active or latent form while working in hospitals. “This research was proposed by a recent medical college graduate, Mada Alsharif, who noticed a rise in positive turberculin skin tests (TST) in medical students who completed their clinical training,” explains Amr S. Albanna of the King Saud Bin Abdulaziz University for Health Sciences, who led the research team. 

The researchers analysed TB screenings of 2,000 undergraduate students who were enrolled in a degree in medicine, dentistry, nursing, pharmacy, radiology, physiotherapy, laboratory science or nutrition between 2010 and 2017. Students were tested for M. tuberculosis infection before and after their hospital training, and those with an active TB were excluded at the beginning of the study.

Among 1997 students, the initial test detected TB in 6% of the students across the different disciplines, and 10% of the remaining students had a positive test after their clinical training. The researchers observed a significant difference between trainees in different specialities, with medical students having the highest risk of developing LTBI (14.6%). The least at risk were those who specialised in nutrition (4.6%) and laboratory science (5.4%). The length of the training or internship, which was 25 months on average, did not affect the likelihood of infection. 

The researchers also noted that less than 50% of the students who tested positive for LTBI were prescribed isoniazid, an antibiotic prophylactic therapy recommended by the WHO to prevent the progression from LTBI to active TB.

“Our study shows that medical students are a vulnerable group and should have adequate training to learn how to protect themselves from TB. During hospital practice, I recommend an annual TB screening and prophylactic treatment for those who develop latent tuberculosis infection,” says Albanna. 

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