Laboratory
Smear conversion rate
Proportion of treated patients who convert from sputum smear-positive to sputum smear-negative within a specified period of time, usually after 2 or 3 months of the initial phase of tuberculosis treatment. It is not a true rate.
Second-line line probe assays (LPAs)
Molecular tests for detection of resistance to fluoroquinolones and injectable anti-tuberculosis drugs.
Phenotypic drug susceptibility testing (DST)
Phenotypic testing determines if an isolate is resistant to an anti-tuberculosis drug by evaluating growth (or metabolic activity) in the presence of the drug. Also called conventional DST.
Line-probe assay (LPA)
Rapid technique based on polymerase chain reaction (PCR) that is used to detect the most common mutations of M. tuberculosis that confer resistance to anti-tuberculosis drugs. It is also used to detect the species of multiple nontuberculous mycobacteria.
Critical proportion
The proportion of resistant M. tuberculosis bacilli within a particular cultured isolate that is used to determine resistance to a particular drug. A 1% critical proportion is used to differentiate susceptible and resistant isolates.
Bacilli
Rod-shaped bacteria
Acid-fast bacilli (AFB) examination
Laboratory test that involves microscopic examination of a stained smear of a patient specimen (usually sputum) to determine if mycobacteria are present.
