Sputum processing prior to Mycobacterium tuberculosis detection by culture or nucleic acid amplification testing: a narrative review
Sputum is a complex specimen consisting of a primary network comprised of linked mucin molecules and a secondary network composed of filamentous actin, cell debris and DNA. Other components of sputum are leukocytes, proteoglycans, inflammatory mediators and elastin fibres. Embedded within this matrix are bacteria which are targeted for clinical diagnosis. This is further complicated in tuberculosis as mycobacteria frequently clump within the specimen resulting in unequal distribution. Efficient release of bacteria from sputum specimens requires chemical and/or mechanical breakdown of both primary and secondary sputum networks. This review gives an overview of the composition of sputum and of various methods that have been used for digesting sputum prior to testing for tuberculosis.
Veronica Allen, Mark P. Nicol, Lemese Ah Tow