Role of mantoux test in the diagnosis of tuberculosis.

A 45-year-old patient from rural community presented with cough of three months associated with weight loss and excessive tiredness. He had no significant past medical history. On examination of the chest, coarse crepitations were heard on the right apical region. His haemoglobin is 9 gm%, total white is 10x109/L and the erythrocyte sedimentation rate (ESR) is 90 mm/hour. His chest radiograph showed right upper zone opacity. Mantoux test was performed on his forearm (Figure 1). Mantoux test is performed by injecting a standard dose of 5 Tuberculin units (0.1ml) into the skin intradermally.1 The result should be read between 48-72 hours after the test and the indurated area is measured in millimeter units.1 The skin reaction following Mantoux test is a form of cell mediated delayed hypersensitivity (Type IV) reaction of the skin. These reactions are mediated by skin macrophages, monocytes and T cells. T cells which are sensitized by prior tuberculous infection migrate to the test site and release lymphokines. The lymphokines then induce inflammatory process, which include erythema, oedema, fibrine deposits and macrophages migration to the sites.1,2 The whole process take place up to 72 hours and the reaction is completed by formation of skin induration. Some may have more severe reaction manifest with vesiculation and skin necrosis. Conditions reported to be associated with reduced Mantoux reactivity include elderly patients, severe hypoalbuminaemia and disseminated tuberculosis (TB).3