In the Journals

Latent TB may be underestimated in corticosteroid users

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July 1, 2014

Patients who receive oral corticosteroids are at greater risk for developing active tuberculosis, but this vulnerable population is screened less often for tuberculosis than others, and they are less likely to receive antibiotic prophylaxis, according to new study results published in the European Respiratory Journal.

Recent data suggest that patients with latent Mycobacterium tuberculosis infection who are prescribed corticosteroids at a dose of >15 mg per day for 2 to 4 weeks or more are at an eightfold increased risk for developing active TB, according to background information in the study. Current treatment guidelines recommend a threshold of ≥5 mm induration following a tuberculin skin test to identify latent TB infection in corticosteroid recipients.

However, Nicholas Vozoris, MD, a respirologist at St. Michael’s Hospital in Toronto, and colleagues suggest that the ≥5 mm cutoff is not evidence-based and should be lowered.

Nicholas Vozoris, MD 

Nicholas Vozoris

The researchers examined data on 7,317 individuals from the National Health and Nutrition Examination Survey, which was designed to assess the health and nutritional status of US adults and children. Of those individuals, 1.3% were oral corticosteroid recipients.

Vozoris and colleagues found that fewer oral corticosteroid recipients (3.1%) than non-recipients (6.1%) demonstrated a positive tuberculin skin test, as defined by an induration of ≥5 mm, but this finding was not significant (P=.22).

According to the researchers, the lower prevalence of latent TB among corticosteroid recipients is likely misleading and the result of the drugs’ known ability to suppress reactivity to skin tests. Assuming that oral corticosteroid recipients have the same prevalence of latent TB as non-recipients (ie, 4.1% based on a threshold of ≥10 mm induration applied to the general population), a cutoff of approximately 3.5 mm induration would be needed for patients who receive corticosteroids to achieve the same prevalence of latent TB infection as non-recipients.

In addition, results indicated that fewer corticosteroid recipients had undergone tuberculin skin testing vs. non-recipients (62.9% vs. 71.6%; P=.07), and fewer recipients received antibiotic prophylaxis (0% vs. 44.3%; P=.54) — factors that may be contributing to the development of active TB in this vulnerable population.

“In conclusion, the current guideline-recommended [tuberculin skin test] threshold of ≥5 mm to denote positivity among recipients of oral corticosteroids may need to be lowered to ~3.5 mm in order to adequately capture [latent TB infection] in this at-risk group, but further research with prospective data and adjustment for confounders is required,” the researchers wrote.

Disclosure: The researchers report no relevant financial disclosures.

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