Abstract: A method of detecting active TB in the presence of a complicating factor, for example, latent TB and/or co-morbidities, such as those that present similar symptoms to TB. The disclosure also relates to a minimal gene signature employed in the said method and to a bespoke gene chip for use in the method. The disclosure further relates to use of gene chips and primer sets in the methods of the disclosure and kits comprising the elements required for performing the method. The disclosure also relates to use of the method to provide a composite expression score which can be used in the diagnosis of TB, particularly in a low resource setting.