Improvement in the diagnosis of tuberculosis in human immunodeficiency virus patients in Central America. Ohio University/IDEI

This project aims for the first time in Central America to implement a Point-of-care (POC) test for the diagnosis of tuberculosis (TB) in human immunodeficiency virus (HIV) patients. A similar project has been previously carried out in Sub-Saharan Africa with great success. The results of this study will serve to guide later validation test studies with the possibility of improving the clinical algorithm of TB diagnosis in HIV positive patients.


NARRATIVE SUMMARY

At present, the acid-fast bacilli (AFB) stain is the most commonly employed method to diagnose active TB in Guatemala. When a patient is suspected of having M. tuberculosis three AFB smears are collected, processed and registered.

Confirmation of TB cases is not, however, routinely performed and cases of negative AFB smears are not completely diagnosed. More than 50% of pulmonary TB cases and 20% of extra-pulmonary TB amongst co-infected HIV-TB are AFB negative. In addition, in many cases patients who suspect they have TB are not able to return to the hospital for sputum collection for the AFB test or do not come back for their results. As a consequence, AFB diagnosis with sputum is only carried out in less than half of the real TB cases.

A diagnostic test with a high sensitivity and specificity to detect TB in HIV-TB co-infected patients is urgently needed. Lipoarabinomannan (LAM) is a lipoglycan present in the cell wall of M. tuberculosis which is excreted in the urine of TB patients. A recently developed diagnostic test, Alere Determine ™ , is based on the detection of urinary LAM. During TB infection its presence represents the metabolization of bacteria by leucocytes or the death of these infected cells.

Determine ™ TB LAM Ag is a simple test that consists of depositing 60 μl urine on a tape impregnated with LAM antibodies. After 25 minutes the test can be interpreted as positive, negative or invalid. It is considered to be a POC test that is easy to use, fast, and economic that will permit early diagnosis and improve the patient's results and treatment. A fast diagnosis also improves control of the infection and diminishes its transmission within the community.

The co-infected HIV-TB population suffers from a considerable delay in diagnosis and an elevated morbi-mortality due to the difficulty and cost of diagnosis and treatment. Many of these patients have no access to treatment and correct follow-up. All of which adds to the stigma and discrimination associated with both diseases and worsens the negative social and economic consequences for the people who are suffering from them. One of the main objectives of this study is to decrease the time of diagnosis for TB in HIV patients and thus improve their follow-up so as to better their prognosis and reduce transmission.