Improved laboratory diagnosis of tuberculosis--the Indian experience.

Tuberculosis (TB) is the leading cause of death worldwide attributable to a single infectious disease agent. India has more new TB cases annually than any other country. In 2008, India accounted for a fifth of the estimated 9.4 million TB cases globally. There is an overwhelming need for improving TB diagnostics in India through the use of cost effective, patient-friendly methods appropriate to different tiers of the country health system. Substantial progress has been made in India in the field of TB diagnosis and serious efforts have been made to herald the development of diagnostic tests for pulmonary TB, extra pulmonary TB and MDR-TB. Diverse approaches have been attempted towards improving smear microscopy, rapid culture and for differentiation between the Mycobacterium tuberculosis complex and non-tuberculous mycobacteria. Several laboratories have developed in-house PCR assays for diagnosing TB with high accuracy. Approaches for distinguishing M. tuberculosis and/or Mycobacterium bovis infection and disseminated Mycobacterium avium complex infection in HIV-AIDS patients have also been described. Serological tests to detect antigens or antibodies to M. tuberculosis specific components by using cocktails of Excretory/Secretory protein antigens, Ag85 complex antigens, Hsp 65 antigen, RD1 antigens and Rapid Reverse Line Blot Hybridization assays to detect MDR-TB (mutations to rifampicin, isoniazid and streptomycin) have also been developed. Other methods like measurement of adenosine deaminase activity and use of luciferase reporter phages have also been explored for TB diagnosis. These advances in the Indian context are detailed in the present chapter. The validation and application of these methods in laboratory and public health settings is likely to result in improved TB diagnosis and contribute to effective disease management in India.

Verrucous tuberculid mimicking Kyrle disease.

Cutaneous tuberculosis shows wide clinical variation depending upon the virulence of the organism and host immunity. Tuberculids are difficult to diagnose since the organism often cannot be identified or isolated by microscopy, culture or polymerase chain reaction. The diagnosis rests primarily on the identification of a tuberculous focus elsewhere in the body and response to antitubercular therapy. We present the clinicopathological features of an unusual tuberculid in a 30-year-old man, remarkably mimicking Kyrle's disease. He presented with multiple, symmetrically distributed follicular and perifollicular verrucous papules, nodules and plaques on the face, earlobes and extremities since 4 years. Histopathology revealed parakeratotic follicular plug invaginating into the dermis with multiple caseating epithelioid cell granulomas. PCR for M. tuberculosis was negative. The identification of associated axillary tubercular lymphadenitis, strongly positive Mantoux reaction, tuberculoid granulomas on histopathology and complete resolution of the lesions with antitubercular therapy helped in making the diagnosis. We propose the term "verrucous tuberculid" for this entity.