The TB IgG/IgM Rapid Test is a sandwich lateral flow chromatographic immunoassay for the simultaneous detection and differentiation of IgM anti-Mycobacterium Tuberculosis (M.TB) and IgG anti- M.TB in human serum or plasma. It is intended to be used as a screening test and as an aid in the diagnosis of infection with M. TB. Any reactive specimen with the TB IgG/IgM Rapid Test must be confirmed with alternative testing method(s) and clinical findings.
Tuberculosis is a chronic, communicable disease caused principally by M. TB hominis (Koch’s bacillus), occasionally by M. TB bovis. The lungs are the primary target, but any organ may be infected. The risk of TB-infection has exponentially declined in the 20th century. However, the recent emergence of drug-resistant strains, particularly among patients with AIDS, has rekindled interest in TB. The incidence of infection was reported around 8 million cases per year with a death rate of 3 million per year. The mortality exceeded 50% in some African countries with high HIV rates. The initial clinical suspicion and radiographic findings, with subsequent laboratory confirmation by sputum examination and culture are the traditional method(s) in the diagnosis of active TB. However, these methods either lack sensitivity or are time consuming, in particularly are not suitable for patients who are unable to produce adequate sputum, smear-negative, or suspected to have extra-pulmonary TB. The TB IgG/IgM Rapid Test is developed to alleviate these obstacles. The test detects IgM and IgG anti-M.TB in serum or plasma in 10 minutes. An IgM positive result indicates for a fresh M.TB infection, while an IgG positive response suggests a previous or latent infection. Utilizing M.TB specific antigens, it also detects IgM anti-M.TB in patients vaccinated with BCG. In addition, the test can be performed by untrained or minimal skilled personnel without cumbersome laboratory equipment.
Principle of The Test
The TB IgG/IgM Rapid Test is a lateral flow chromatographic immunoassay. The test cassette consists of: 1) a colored conjugate pad containing M.TB antigens conjugated with colloid gold (M.TB conjugates) and rabbit IgG-gold conjugates, 2) a nitrocellulose membrane strip containing two test lines (T1- and T2-line) and a control line (C-line). The T1-line is pre-coated with monoclonal anti-human IgM for the detection of IgM anti- M.TB, the T2-line is pre-coated with reagents for the detection of IgG anti-M.TB, and the C-line is pre-coated with goat anti-rabbit IgG. When an adequate volume of test specimen is dispensed into the sample well of the cassette, the specimen migrates by capillary action across the membrane. IgM anti-M.TB if present in the specimen will bind to the M.TB conjugates. The immunocomplex is then captured on the membrane by the pre-coated anti-human IgM antibody, forming a burgundy colored T1- line, indicating a M.TB IgM positive test result. IgG anti- M.TB, if present in the specimen, will bind to the M.TB conjugates. The immunocomplex is then captured by the precoated reagents on the membrane, forming a burgundy colored T2-line, indicating a M.TB IgG positive test result. Absence of any T lines (T1 and T2)suggests a negative result. The test contains an internal control (C-line) which should exhibit a burgundy colored line of the immunocomplex of goat anti rabbit IgG/rabbit IgG-gold conjugate regardless of the color development on any of the T-lines. Otherwise, the test result is invalid and the specimen must be retested with another device.