Evaluation of a LAM FLISA for the Diagnosis of Tuberculosis

Tuberculosis is a bacterial infection causing 1.1 million deaths annually worldwide. Diagnosis of the disease is often time consuming or challenging. Many cases of tuberculosis require advanced and expensive diagnostic methods that restrict their availability in resource limited countries where the burden of tuberculosis is highest. The development of rapid point of care diagnostics is required.

Lipoarabinomannan (LAM) is part of the bacterial cell wall in M. tuberculosis. It is released when bacteria are multiplying or dying. LAM can be detected in the urine since it is filtered from the blood in the kidneys. The detection of LAM in the urine by conventional enzyme linked immuno-sorbent assay (ELISA) techniques was hampered in the past by a low sensitivity and multiple processing steps. Recently, fluorescence linked immuno-sorbent assay (FLISA) has been shown to detect LAM in concentrations that are several magnitudes lower that with ELISA based methods. Furthermore the procedure requires less separate steps for processing the sample.

This study aims to validate the new diagnostic test by comparing patients with (a) confirmed tuberculosis (n=25), (b) infection with non-tuberculous mycobacteria (n=25), (c) bronchial carcinoma (n=25), (d) suspected tuberculosis but confirmed alternative diagnosis (estimated n=20). Single blood and urine samples of these groups will be used to evaluate the sensitivity and specificity of the test.

In patients with confirmed tuberculosis the LAM FLISA will also be assessed as a biomarker for the monitoring of tuberculosis treatment success. Initially, 2-5 samples blood and urine are required during the first week, followed by twice weekly and weekly sampling intervals over a period of 12 weeks maximum. The study participation ends when the patient is discharged from hospital.

As a substudy, the blood samples will be used to evaluate an enzyme linked immuno-sorbent assay (ELISA) for the detection of lipid antigens that are specific for Mycobacterium tuberculosis.