Zinc Cream and Reliability of Tuberculosis Skin Testing
Zinc Cream and Reliability of Tuberculosis Skin Testing
In 50 healthy Peruvian shantytown residents, zinc cream applied to tuberculosis skin-test sites caused a 32% increase in induration compared with placebo cream. Persons with lower plasma zinc had smaller skin-test reactions and greater augmentation with zinc cream. Zinc deficiency caused false-negative skin-test results, and topical zinc supplementation augmented antimycobacterial immune responses enough to improve diagnosis.
Tuberculosis (TB) kills >1.7 million people each year, and control is hampered by diagnostic difficulties. The TB (Mantoux) skin test measures the immune response to an intradermal injection of tuberculin (purified protein derivative [PPD]) and is important for diagnosing adult and particularly pediatric TB. However, reliability of this skin test is limited by false-negative results, especially in poorly nourished people in the resource-limited settings where most cases of TB occur. Zinc is implicated in false-negative skin tests because it modulates cutaneous reactions, because zinc deficiency is common in people with TB, and because this deficiency also suppresses antimycobacterial immunity. We therefore studied whether topical application of zinc to TB skin test sites would augment test results in Lima, Peru, a TB-endemic area in which false-negative skin-test results are frequent.
Abstract and Introduction
Abstract
In 50 healthy Peruvian shantytown residents, zinc cream applied to tuberculosis skin-test sites caused a 32% increase in induration compared with placebo cream. Persons with lower plasma zinc had smaller skin-test reactions and greater augmentation with zinc cream. Zinc deficiency caused false-negative skin-test results, and topical zinc supplementation augmented antimycobacterial immune responses enough to improve diagnosis.
Introduction
Tuberculosis (TB) kills >1.7 million people each year, and control is hampered by diagnostic difficulties. The TB (Mantoux) skin test measures the immune response to an intradermal injection of tuberculin (purified protein derivative [PPD]) and is important for diagnosing adult and particularly pediatric TB. However, reliability of this skin test is limited by false-negative results, especially in poorly nourished people in the resource-limited settings where most cases of TB occur. Zinc is implicated in false-negative skin tests because it modulates cutaneous reactions, because zinc deficiency is common in people with TB, and because this deficiency also suppresses antimycobacterial immunity. We therefore studied whether topical application of zinc to TB skin test sites would augment test results in Lima, Peru, a TB-endemic area in which false-negative skin-test results are frequent.
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