Diagnosis
Weak positive culture
One to nine colonies of M. tuberculosis detected.
WHO four-symptom screen
The presence of either cough, fever, weight loss, or night sweats used as a screening test in people living with HIV.
Tuberculin skin test (TST) conversion rate
Proportion of a population in which TST results converted within a specified time. It is calculated by dividing the number of TST conversions among persons in the setting in a specified period (numerator) by the number of persons who received TSTs in the setting over the same period (denominator), multiplied by 100. It is not a true rate.
Triage test for tuberculosis
A test that can be rapidly conducted among people presenting to a health facility to differentiate those who should have further diagnostic evaluation for tuberculosis from those who should undergo further investigation for non-tuberculosis diagnoses.
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.
Smear microscopy
Test to see whether there are mycobacteria in a particular specimen (sputum or an extrapulmonary sample). To do this test, lab workers smear the specimen on a glass slide, stain the slide with a special dye, and look for any mycobacteria on the slide. Also known as acid fast bacilli (AFB) examination.
Second-line line probe assays (LPAs)
Molecular tests for detection of resistance to fluoroquinolones and injectable anti-tuberculosis drugs.
Provider-initiated tuberculosis screening pathway
The provider-initiated tuberculosis screening pathway systematically targets people at high risk of exposure or of developing tuberculosis and screens them by assessing symptoms, using tests, examinations, or other procedures to identify those who might have tuberculosis, following up with a diagnostic test and additional clinical assessments to make a definite diagnosis.
Proportion method
The most common method used for testing the susceptibility of M. tuberculosis complex isolates. In this method, the inoculum used is monitored by testing two dilutions of a culture suspension, and the growth (that is, the number of colonies) on a control medium without an anti-tuberculosis agent is compared with the growth (the number of colonies) present on a medium containing the critical concentration of the anti-tuberculosis drug being tested.
Mtb antigen-based skin tests (TBST)
Skin tests for the detection of M.tuberculosis that use Mtb specific antigens (ESAT6 and CFP10).
