Diagnosis of tuberculosis for HIV patients has certain features depending on the stage of AIDS and the number of CD4 lymphocytes in the blood of the patient.
At the initial stage of HIV course of pulmonary tuberculosis is almost the same as the specific affection of HIV-negative patients. At this standard forms of pulmonary tuberculosis are developing, with a predominance of infiltrative processes, with the collapse of lung tissue and release of bacteria. Diagnosis is based on standard methods of compulsory clinical examination, which consists of a study of patient’s history, physical examination, clinical blood and urine tests, chest radiography, 3-fold microscopic examination of sputum for nourishing environment, assessment of intradermal Mantoux test with 2 TE PPD-L.
However, against the HIV background verification of TB is much more difficult because of atypical clinical, radiological, immunological features of tuberculosis. Global standard of TB detection is sputum smear microscopy and culture method. The sensitivity of microscopy is 67%, for immunosuppressed – 50%. Culture method is time-consuming due to the fact that mycobacterium tuberculosis grow very slowly and their colonies can be seen only by 2-2.5 month, but late TB diagnosis causes the death of a patient in 45-85% of cases.
So in the world of show less than 25% of cases of infection of tuberculosis combined with HIV infection. The solution quickly and efficiently diagnosing TB in HIV-infected are putting into practice of laboratory tests for tuberculosis enzyme multiplied immunoassay method that can detect antigens and antibodies. However, given that the antimycobacterial antibodies are weakly against the background immunosuppression, as well as background processes pryhnychennya agent induced the formation of antibodies in the blood and reduce free antibody ELISA Diagnosis should be based on direct determination of antigens.
Currently the most promising method for TB detection with high sensitivity and specificity for immunosuppressive individuals is direct determination of highly immunogenic antigen for Mycobacterium tuberculosis Complex – lipoarabinomannan in urine (Lam-antigen).
The quality of this method is highly appreciated in the global clinical practice. Studies indicate a high sensitivity of this test (80%) compared to traditional methods. This diagnostic method can be applied not only to HIV patients but also to people with weakened immune status, for example long administration of hormones and cytotoxic drugs and for TB diagnosis in children.
ELISA test system “TB LamAg-MBA” is intended for the qualitative detection of LAM-antigen in urine of HIV patients with symptomatic tuberculosis by solid-state ELISA. The set is designed for 96 tests including control and used exclusively for urina tests.
This test does not differentiate mycobacteria by type, such as for example M.tuberculosis, M.leprae, M.avium. But in most cases, the presence of LAM-antigen in the sample means infection by Micobacterium tuberculosis, as LAM-antigen found in endemic areas refers to Micobacterium tuberculosis. However, to confirm a positive result it is necessary to re-test the specimen by culture method.