Tuberculin skin test and anergy in dialysis patients of a tuberculosis-endemic area.
OBJECTIVE
Uremic patients are at an increased risk of being affected by tuberculosis (TB). Periodical tuberculin skin tests were suggested to detect TB-infected patients. These were replaced by chest radiographs in endemic areas like Taiwan. However, almost 50% of the TB incidence in dialysis patients was extrapulmonary. In this study, we tried to investigate the value of tuberculin tests in dialysis patients in endemic areas.


METHODS
The patients were recruited from our dialysis unit. Purified protein derivative (PPD) and control tests with antigens for Candida and toxoid were performed using the Mantoux method. PPD with >10-mm induration will be considered positive. Skin anergy meant that the indurations of all antigens were less than 5 mm. A follow-up was done 12 months after the tests.


RESULTS
A total of 177 patients were evaluated. Anergy was found in 40 patients (22.6%). A positive predictor of anergy was age >45 years (p = 0.03), while a negative predictor was prealbumin >20 mg/dl (p = 0.04). Fifty-three patients (30%) had positive PPD tests. Seven of the positive PPD patients (13.2%) developed active TB during the following years. Among the 40 patients with skin anergy, 6 (15%) were found to have active TB. Of the 48 patients (21.1%) with indurations of the PPD tests between 5 and 10 mm, none was found to have active TB.


CONCLUSIONS
Although anergy will influence the sensitivity of PPD tests, these tests in combination with anergy tests could help to establish the diagnosis of TB in uremic patients, even in TB-endemic areas.
Division of Nephrology, Department of Internal Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
Hua-Chang
HC
Fang
Kang-Ju
KJ
Chou
Chien-Liang
CL
Chen
Po-Tsang
PT
Lee
Yee-Hsuan
YH
Chiou
Shih-Yuan
SY
Hung
Hsiao-Min
HM
Chung
D000328:Adult; D000368:Aged; D017635:Clonal Anergy; D019353:Endemic Diseases; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis; D013624:Taiwan / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology