The prevalence of tuberculin sensitivity and anergy in chronic renal failure in an endemic area: tuberculin test and the risk of post-transplant tuberculosis.

BACKGROUND Cutaneous sensitivity to the tuberculin antigen is thought to indicate latent tuberculosis infection (LTBI). Some guidelines suggest treating end-stage renal disease (ESRD) patients for LTBI on the basis of tuberculin positivity. The prevalence of tuberculin sensitivity and cutaneous anergy in Indian patients with ESRD and the utility of the tuberculin test for predicting post-transplant tuberculosis are not known. METHODS We prospectively studied cutaneous tuberculin reactivity and anergy in 108 ESRD patients and 100 age- and sex-matched healthy controls. Mumps antigen and tetanus toxoid were used as control antigens. Patients who failed to react to all antigens were classified as anergic. Seventy-nine patients underwent living donor kidney transplants and were followed-up for approximately 2 years. RESULTS About 44% of ESRD patients and 66% of controls showed tuberculin reactivity (P = 0.0018). The prevalence of anergy was significantly higher in the ESRD population (44% vs 16%, P<0.001). The haemoglobin, serum albumin and creatinine values were significantly higher amongst the tuberculin-reactor ESRD patients. Tuberculin positivity and anergy rates in a subgroup of well-nourished ESRD patients were similar to the control population. Four patients developed tuberculosis after transplantation. Tuberculin test had a sensitivity of 50% and a specificity of 52% for post-transplant tuberculosis. CONCLUSIONS In comparison to healthy controls, tuberculin reactivity rates are lower and anergy rates higher in Indian ESRD patients. There is a significant relationship between markers of nutritional status (haemoglobin, albumin and creatinine) and cutaneous reactivity. Pre-transplant Mantoux positivity has low sensitivity and specificity for predicting post-transplant tuberculosis.