Serodiagnosis of tuberculous lymphadenitis using a combination of antigens

Abstract

Background: The diagnosis of extra-pulmonary tuberculosis (EPTB) by conventional methods such as culture and microscopy has low sensitivity and requires an invasive procedure. A simple rapid serological test would be of great value.

Methodology: Six antigens (ESAT-6, Ag85A, TB10.4, Rv3881c, lipoarabinomannan (LAM) and Ara₆-BSA) were tested in an ELISA to detect antigen-specific IgG and IgM antibodies in sera from 54 culture- and histology-confirmed tuberculous lymphadenitis (TBLN) patients as follows: four were HIV seropositive; sera from 25 was smear positive for pulmonary tuberculosis (PTB); 15 were culture- and histology-negative lymphadenitis (non-TBLN) patients; and 22 werehealthy controls (HCs).

Results: The sensitivities of the antigens for the detection of IgG in sera of TBLN patients ranged from 4% to 30%. Specificities ranged from 73% to 100% with sera from non-TBLN patients and 91% to 100% with sera from HCs. Sensitivities of the antigens for detection of IgM ranged from 0% to 15% and specificities ranged from 80% to 100% with sera from non-TBLN patients and 91% to 100% with sera from HCs. LAM was the most potent antigen for detection of IgG. When LAM and ESAT-6 were combined, sensitivity increased up to 43% and specificity with non-TBLN was 80% with HC 96%.

Conclusions: The study suggests that the combined use of LAM and ESAT-6 for IgG antibody detection in sera from TBLN patients could be a supplement to microscopy of fine-needle aspirate (FNA) to diagnose TBLN among patients suspected of TBLN.