A better approach to preventing active TB?

ILLUSTRATIVE CASE

A 27-year-old daycare worker was tested for tuberculosis (TB) as part of a recent work physical. She presents to your office for follow-up for her positive purified protein derivative (PPD) skin test. You confirm the result with a quantiferon gold test and ensure she does not have active TB. What medication should you prescribe to treat her latent TB infection (LTBI)?

In 2017, there were 9093 cases of new active TB in the United States.² It’s estimated that one-fourth of the world’s population has latent TB.³ Identifying and treating latent TB ­infection is vital to achieving TB’s elimination.^4,5

Primary care clinicians are at the forefront of screening high-risk populations for TB. Once identified, treating LTBI can be challenging for providers and patients. Treatment guidelines recommend 4 to 9 months of daily isoniazid.^5-8 Shorter treatment regimens were recommended previously; they tended to be rigorous, to involve multiple drugs, and to require high adherence rates. As such, they included directly observed therapy, which prevented widespread adoption.

Consequently, the mainstay for treating LTBI has been 9 months of daily isoniazid. However, isoniazid use is limited by hepatoxicity and by suboptimal treatment completion rates. A 2018 retrospective analysis of patients treated for LTBI reported a completion rate of only 49% for 9 months of isoniazid.⁹ Additionally, a Cochrane review last updated in 2013 suggests that shorter courses of rifampin are similar in efficacy to isoniazid (although with a wide confidence interval [CI]), and likely have higher adherence rates.¹⁰

STUDY SUMMARY

Rifampin is as effective as isoniazid with fewer adverse effects

The study by Menzies et al¹ was a multisite, 9-country, open-label, randomized controlled trial (RCT) that compared 4 months of daily rifampin to 9 months of daily isoniazid for the treatment of LTBI in adults. Participants were eligible if they had a positive tuberculin skin test or interferon-gamma-release assay, were ≥ 18 years of age, had an increased risk for reactivation of active TB, and if their health care provider had recommended treatment with isoniazid. Exclusion criteria included current pregnancy or plans to become pregnant, exposure to a patient with TB whose isolates were resistant to either trial drug, an allergy to either of the trial drugs, use of a medication with serious potential interactions with the trial drugs, or current active TB.

Method, outcomes, patient characteristics. Patients received either isoniazid 5 mg/kg body weight (maximum dose 300 mg) daily for 9 months or rifampin 10 mg/kg (maximum dose 600 mg) daily for 4 months and were followed for 28 months. Patients in the isoniazid group also received pyridoxine (vitamin B₆) if they were at risk for neuropathy. The primary outcome was the rate of active TB. Secondary outcomes included adverse events, medication regimen completion rate, and drug resistance, among others.

This study found that a shorter rifampinbased regimen is associated with improved adherence and fewer adverse events than a longer isoniazid-based regimen for the treatment of latent TB infection.

A total of 2989 patients were treated with isoniazid; 3023 patients were treated with rifampin. The mean age of the participants was 38.4 years, 41% of the population was male, and 71% of the groups had confirmed active TB in close contacts.

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