Recommendations From Others
The Centers for Disease Control and Prevention (CDC) and the American Thoracic Society joint guidelines for the treatment of latent TB infection state that baseline laboratory testing is not routinely indicated, even for persons aged >35 years, but may be considered for patients who are taking other hepatotoxic medications or have chronic medical conditions.11
Baseline measurements of bilirubin and aspartate transaminase (AST) or alanine transaminase (ALT) along with monthly liver function test monitoring are recommended for patients with pre-existing liver disease, patients at risk for chronic liver disease, patients with HIV infection, pregnant or postpartum women, and regular users of alcohol. All patients should be evaluated at least monthly for symptoms of hepatitis, and liver function tests should also be obtained for patients with symptoms compatible with hepatotoxicity. The guideline suggests that isoniazid be stopped if liver function tests exceed 5 times the upper limits of normal, or 3 times the upper limits of normal if the patient is symptomatic. The Canadian Tuberculosis Standards (5th ed, 2000) recommend baseline AST before isoniazid preventive therapy is started, and regular monitoring in those with pre-existing liver disease, a history of ethanol abuse, or age ≥35 years.12
CLINICAL COMMENTARY
Patients need to understand risks and benefits of TB treatment
Lauren DeAlleaume, MD
University of Colorado Health Sciences Center, Denver
As the number of immigrants increases, FPs will see more patients at high risk for TB. Patients whose risk of developing active TB exceeds the risk of isoniazid toxicity should be tested (targeted testing). It is challenging to ensure an asymptomatic patient completes a 9-month course of therapy while undergoing monthly monitoring for symptoms of isoniazid toxicity. Overall, only 60% of patients complete a full course of isoniazid. Clinical and public health systems that make it easier for patients to follow-up can enhance compliance.
Patients need to understand the benefits of treatment and the symptoms of isoniazid toxicity. The CDC recommends clinical monitoring without routine blood testing for patients of any age without additional risk factors for isoniazid hepatitis. Excessive monitoring can lead to premature discontinuation of therapy because 10%–20% of patients develop some liver function test elevation. The CDC has an excellent course on the basics of latent TB testing and treatment ( at www.phppo.cdc.gov/phtn/tbmodules/Default.htm). Patient education materials and risk assessment and monitoring forms can be obtained from state health departments.