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Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Immunochromatographic IgG/IgM test for rapid diagnosis of active tuberculosis
Walid Ben-Selma1, Hedi Harizi, Jalel Boukadida
1Microbiology and Immunology Laboratory, UR02SP13, CHU Farhat Hached, Av. Ibn el Jazzar 4000, Sousse, Tunisia. wbenselma@hotmail.com
Insights
A rapid test detecting IgG antibodies against mycobacterial antigens shows promise for diagnosing active tuberculosis (TB). This test offers high specificity and could be a valuable screening tool for TB in resource-limited settings.
Area of Science:
- Immunology
- Infectious Diseases
- Medical Diagnostics
Background:
- Tuberculosis (TB) diagnosis requires rapid and accurate methods, especially for differentiating it from other pulmonary diseases.
- Current diagnostic tools may have limitations in accessibility and speed, particularly in resource-limited settings.
Purpose of the Study:
- To evaluate the clinical utility of a commercial rapid immunochromatographic test for detecting serum IgG and IgM antibodies against specific mycobacterial antigens.
- To assess the test's effectiveness in diagnosing active TB (pulmonary and extrapulmonary) and distinguishing it from non-TB pulmonary conditions.
Main Methods:
- A commercial rapid immunochromatographic IgG/IgM test was used to analyze 246 serum samples.
- Samples were from patients with active TB (pulmonary and extrapulmonary), pulmonary non-TB diseases, and leprosy.
- Antibodies against mycobacterial 38-kDa, 16-kDa, and 6-kDa antigens were targeted.
Main Results:
- The IgG test demonstrated high specificity (100%) and promising sensitivity for active pulmonary TB (78.1%) and extrapulmonary TB (39.5%).
- IgM antibody detection showed low sensitivity (2.3%) for active TB.
- Combining IgG and IgM did not enhance the overall sensitivity of the test.
Conclusions:
- Serum IgG antibodies against mycobacterial antigens show potential as a tool for the presumptive diagnosis and discrimination of active pulmonary TB.
- The test's simplicity and speed make it a potential screening tool for active TB in laboratories with limited resources.
Abstract:
For rapid diagnosis and discrimination between active tuberculosis (TB) and other pulmonary diseases, we evaluated the clinical usefulness of detection of serum immunoglobulin IgG and IgM antibodies raised against mycobacterial 38-kDa, 16-kDa, and 6-kDa antigens by a commercial rapid immunochromatographic IgG/IgM test (Standard Diagnostics, South Korea) in 246 serum samples from three groups of patients: (i) 171 patients with active TB (128 with pulmonary TB [pTB] and 43 with extrapulmonary TB [epTB]), (ii) 73 patients with pulmonary non-TB diseases, and (iii) two leprosy patients. The sensitivities of IgG and IgM in patients with active TB (pTB and epTB) were 68.4% and 2.3%, respectively. IgG had the best performance characteristics, with sensitivities of 78.1% and 39.5% in sera from patients with active pTB and epTB, respectively, and a specificity of 100%. The sensitivities of IgM were poor and were similar for pTB and epTB (2.3%). In contrast, specificity was very elevated (100%). The combination of IgG with IgM did not improve its sensitivity. IgG-mediated responses against the mycobacterial 38-kDa, 16-kDa, and 6-kDa antigens might constitute a clinically useful tool for presumptive diagnosis and discrimination of active pTB from other pulmonary diseases. Moreover, based on its simplicity and rapidity of application, it could be a screening tool for active pTB in poorly equipped laboratories.
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