Diagnosis
Purified protein derivative (PPD), tuberculin
Material used in diagnostic tests to measure immune reactivity to past or present M. tuberculosis infection. PPD is a purified tuberculin preparation that was developed in the 1930s and derived from old tuberculin. It is administered as part of a tuberculin skin test (TST) that is given as an intradermal injection of 0.1 ml containing 5 TU (Mantoux method) and read 48–72 hours later.
Passive case-finding
Patient-initiated pathway to tuberculosis diagnosis involving a person with tuberculosis who experiences symptoms that they recognize as serious; the person having access to and seeking care and presenting spontaneously at an appropriate health facility; a health worker correctly assessing that the person fulfils the criteria for presumptive tuberculosis; and successful use of a diagnostic algorithm with sufficient sensitivity and specificity to diagnose tuberculosis.
Minimum inhibitory concentration (MIC)
The lowest concentration of an antimicrobial agent that prevents growth of more than 99% a microorganism in a solid medium or broth dilution susceptibility test.
Mantoux method
It is the recommended technique to perform the purified protein derivative (PPD)-based tuberculin skin test (TST). It consists of the injection of 0.1 ml containing 5 tuberculin units (TU) of PPD intradermally into the volar or dorsal surface of the forearm.
Drug-susceptible tuberculosis
Disease caused by a strain of M. tuberculosis that is susceptible to the most commonly used anti-tuberculosis drugs (isoniazid, rifampicin, pyrazinamide, and ethambutol).
Conversion of interferon-Γ release assays
Change from a negative to a positive result as per manufacturer’s threshold.
Cross-resistance
Resistance to multiple anti-tuberculosis agents caused by a single genetic change (or multiple changes, in case the given resistance mechanisms require several genetic alterations).
Cavity
An air-filled space within lung consolidation. Consolidation may resolve and leave only a thin wall.
Computer-aided detection (CAD) for tuberculosis
The use of specialized software to interpret abnormalities on chest radiographs that are suggestive of tuberculosis. The results are expressed as abnormality scores. CAD may be used for screening or triage.
Bacteriologically confirmed tuberculosis (case definition)
Tuberculosis occurring in a patient from whom a biological specimen tests positive by smear microscopy, culture or WHO-recommended rapid diagnostic. Also known as laboratory or microbiologically confirmed tuberculosis case.
