Sensitivity and specificity of the inner thigh, as a site for Mantoux test

Abstract

Background: Early diagnosis, prompt treatment and case finding are vital measures in the management of Tuberculosis (TB), a common infectious disease with a worldwide spread. Mantoux test, a type IV hypersensitivity reaction, is commonly used to screen children for possible TB. It is applied on the volar aspect of the forearm. The estimated sensitivity of Mantoux test on patients with TB disease ranged from 80% to 96%. The test is affected negatively by severe malnutrition and immunosuppression. Sunlight ultraviolet rays (UV) have recently been shown to induce immunosuppression that alters the skin response to Mantoux test negatively.
Objective: To investigate the adequacy of the inner thigh as a site for Mantoux test.
Methods: Concomitant intradermal injection of 0.1ml of purified protein derivative (PPD) on the forearm and the inner thigh was carried out; and induration measured simultaneously in 106 consecutive children, aged 3months to 15 years. The forearm was used as standard to test for sensitivity and specificity of the inner thigh.
Results: Of the 29 subjects with reactive induration, 19(66%) were positive inner thigh and 10(35%) on the volar surface. Inner thigh measurement had a sensitivity of 100% and specificity of 88.5%. The positive and negative predictive values of the inner thigh measurements was 65.5% and 100% respectively while the efficiency was 91%.
Conclusions: The specificity and sensitivity of the inner thigh as a site for the screening and early detection of TB appears strong, it should be considered as a possible site for Mantoux test.

Keywords: Adequacy, children, efficiency, predictive values