Abstract
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. 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, among whom four were HIV seropositive, sera from 25 smear positive pulmonary tuberculosis (PTB) patients, 15 culture and histology-negative lymphadenitis (non-TBLN) patients (n=15) and 22 healthy controls (HCs). The sensitivities of the antigens for the detection of IgG in sera of TBLN patients ranged from 4 to 30 %. Specificities ranged from 91 to 100 % with sera from HCs. Sensitivities of the antigens for detection of IgM ranged from 0 to 15 % and specificities ranged from 91 to 100 %. LAM was the most potent antigen followed by ESAT-6 and Rv3881c for detection of IgG. However, the sensitivity for antigen specific IgG antibody detection was improved when LAM was combined with ESAT-6 and Rv3881c.The sensitivity was 54 % and the specificity 91 %. The study suggests that the combined use of LAM, ESAT-6 and Rv3881c for the detection of IgG in sera of TBLN patients could be a supplement to microscopy of fine- needle aspirate (FNA) to diagnose EPTB.
Highlights
Tuberculosis (TB) is a major public health problem in Ethiopia
This study evaluated the diagnostic potential of six antigens, early secretory antigenic target-6 (ESAT-6), antigen 85A (Ag85A), TB10.4, Rv3881c, LAM and Ara6-BSA, by using sera from TBLN patients, healthy controls (HCs), non-tuberculous lymphadenitis cases and pulmonary tuberculosis (PTB) patients
ESAT-6 followed with a sensitivity of 13% and with a specificity of 96% when HC sera were considered as controls
Summary
Tuberculosis (TB) is a major public health problem in Ethiopia. According to the World Health Organization (WHO) report of 2008 [1], Ethiopia is number 7 among the 22 high TB-burden countries. According to the Ethiopian National TB and Leprosy Control program (NTLC) [2], pulmonary TB (PTB) accounts for 63% of all TB cases and extra-pulmonary TB (EPTB) accounts for 37% of cases, with 80% of EPTB being lymph node TB [2] In spite of these high numbers, diagnosis of tuberculous lymphadenitis (TBLN) remains a challenge. The polymerase chain reaction (PCR) is sensitive and specific but expensive and not available in the majority of health care centers in resource-poor countries These tests involve an invasive procedure to obtain clinical specimens [5]. 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 histologynegative lymphadenitis (non-TBLN) patients; and 22 werehealthy controls (HCs). 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
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