With an estimated annual incidence of over nine million cases, tuberculosis (TB) is believed to be responsible for more adult deaths each year than any other single infectious agent. The highest burden of disease is currently borne by the less developed countries of Africa and Asia where efforts to control TB are hampered by weak health systems and in some settings, by the high prevalence of co-infection with HIV. The recent emergence of multidrugresistant stains that cannot be cured with standard treatments has served to emphasize the urgency of the situation. Control of TB in high burden countries relies on the detection and treatment of infectious cases, most usually by testing patients attending a health clinic that report a cough of at least three weeks duration. The diagnostic tests available in these settings are sputum smear microscopy, an insensitive technique requiring a skilled practitioner and chest radiography, a technique lacking in specificity as well as sensitivity. World Health Organization estimates suggest that in 2006 there were 4 million individuals with undiagnosed tuberculosis. More effective interventions are required to detect and treat infectious cases earlier in the transmission chain, particularly in vulnerable communities with a high prevalence of HIV.
Mycobacterium tuberculosis, the causative agent is spread from person to person via infected aerosols created by patients with respiratory forms of the disease. Bacilli released into the airways following necrosis and destruction of lung tissue may be expelled from the lungs and if released in the form of aerosols may remain airborne and available for inhalation and infection of a new host. Despite being the major mode of transmission there is little data available regarding the exhalation of M. tuberculosis. This paper describes testing of a novel device that utilizes immunosensor and bio-optical technology to detect M. tuberculosis antigen in the breath of humans.
Field test of a novel detection device for Mycobacterium tuberculosis antigen in cough. BMC Infectious Diseases 2010, 10: 161 doi:10.1186/1471-2334-10-161
Tuberculosis is a highly infectious disease that is spread from person to person by infected aerosols emitted by patients with respiratory forms of the disease. We describe a novel device that utilizes immunosensor and bio-optical technology to detect M. tuberculosis antigen (Ag85B) in cough and demonstrate its use under field conditions during a pilot study in an area of high TB incidence.
The TB Breathalyzer device (Rapid Biosensor Systems Ltd) was field tested in the outpatient clinic of Adama Hospital, Ethiopia. Adults seeking diagnosis for respiratory complaints were tested. Following nebulization with 0.9% saline patients were asked to cough into a disposable collection device where cough aerosols were deposited. Devices were then inserted into a portable instrument to assess whether antigen was present in the sample. Demographic and clinical data were recorded and all patients were subjected to chest radiogram and examination of sputum by Ziehl-Nielsen microscopy. In the absence of culture treatment decisions were based on smear microscopy, chest x-ray and clinical assessment. Breathalyzer testing was undertaken by a separate physician to triage and diagnostic assessment.
Sixty individuals were each subjected to a breathalyzer test. The procedure was well tolerated and for each patient the testing was completed in less than 10 min. Positive breath test results were recorded for 29 (48%) patients. Of 31 patients with a diagnosis of tuberculosis 23 (74%) were found positive for antigen in their breath and 20 (64%) were smear positive for acid fast bacilli in their sputum. Six patients provided apparent false positive breathalyzer results that did not correlate with a diagnosis of tuberculosis.
We propose that the breathalyzer device described warrants further investigation as a tool for studying exhalation of M. tuberculosis. The portability, simplicity of use and speed of the test device suggest it may also find use as a tool to aid early identification of infectious cases. We recommend studies be undertaken to determine the diagnostic sensitivity and specificity of the device when compared to microbiological and clinical indicators of tuberculosis disease.