New tuberculosis skin test
SSI is developing a new and improved skin test to diagnose M. Tuberculosis infections, and has achieved excellent results in 2011
Current diagnostic tests for detecting M. tuberculosis infections include the PPD Tuberculin Skin Test (PPD TST) and Interferon gamma release assays (IGRAs). Both systems have specific advantages as well as specific disadvantages. The PPD skin test has proved its value for decades and benefits from the low tech procedure, resulting in low cost and excellent ease of use. The more recently developed IGRAs have their major advantage in their improved specificity in BCG vaccinated populations, but require laboratory facilities.
SSI's new skin test, provisionary named C-Tb, combines the strengths and advantages of both technologies: the low cost and ease of use of the PPD TST and the high specificity of the IGRAs systems.
Thus C-Tb is expected to be able to diagnose a M. tuberculosis infection - regardless of prior BCG vaccination - in a simple well known procedure which will require no laboratory facilities and may be quickly and easily implemented at any site.
The C-Tb will tentatively be applicable in all clinical situations where a diagnosis of M. tuberculosis infection is needed, including:
- Contact tracing in relation to known TB cases
- Serial testing of health care workers
- Screening before initiation of immune suppressing treatment
- Screening of individuals with increased risk of TB for any reason
- TB diagnosis in young children where diagnosis otherwise is difficult
Clinical phase I trials with C-Tb were performed in 2010, and in December 2011, the clinical part of two phase II trials were completed.
Two large Phase III trials are about to commence in 2012, designed to demonstrate the safety of C-Tb and to compare the diagnostic performance of C-Tb to both IGRA and the PPD TST. Both trials are expected to be concluded during 2014.
Last revised 25 January 2012