Hair isoniazid levels predict TB sputum culture conversion

Area of Science:

• Pharmacokinetics and Tuberculosis Treatment Monitoring

Background:

• Sputum culture is the standard for diagnosing tuberculosis (TB) and assessing treatment success.
• Current sputum culture methods have a 6-8 week turnaround time, delaying critical patient management decisions.

Purpose of the Study:

• To determine if isoniazid hair drug levels can predict sputum culture conversion at 8 weeks of TB treatment.

Main Methods:

• 56 TB patients were enrolled and initiated on treatment.
• Sputum and hair samples were collected at baseline and Weeks 4, 8, and 26.
• Sputum cultures were performed using solid and liquid media; hair drug levels were quantified via liquid chromatography-tandem mass spectrometry.

Main Results:

• 28 participants completed the study; 24 (86%) achieved sputum culture negativity.
• Patients with negative sputum cultures had a median hair isoniazid level of 0.0514 ng/ml (IQR 0.1165-0.0314).
• Four patients (14.1%) remained culture-positive, with a median hair isoniazid level of 0.0192 ng/ml (IQR 0.0267-0.0132).

Conclusions:

• A median isoniazid hair concentration of ≥0.05 ng/ml may indicate sputum culture conversion by the end of the intensive phase of TB therapy.