7
➤ The panel recommends that mycobacterial cultures be
performed, rather than not performed, on specimens collected
from sites of suspected extrapulmonary TB (S-L).
Remarks: A positive result can be used as evidence of extrapulmonary TB and guide
decision making because false-positive results are unlikely. However, a negative result
may not be used to exclude TB because false-negative results are exceedingly common.
➤ The panel suggests that NAAT be performed, rather than not
performed, on specimens collected from sites of suspected
extrapulmonary TB (C-VL).
Remarks: A positive NAAT result can be used as evidence of extrapulmonary TB
and guide decision making because false-positive results are unlikely. However, a
negative NAAT result may not be used to exclude TB because false-negative results are
exceedingly common. At present, NAAT testing on specimens other than sputum is an
off-label use of the test.
➤ The panel suggests that histological examination be performed,
rather than not performed, on specimens collected from sites of
suspected extrapulmonary TB (C-VL).
Remarks: Both positive and negative results should be interpreted in the context of the
clinical scenario because neither false-positive nor false-negative results are rare.
➤ The panel recommends a culture isolate from each mycobacterial
culture-positive patient be submitted to a regional genotyping
laboratory for genotyping (S-VL).
Table 1. Essential Laboratory Tests for the Detection of Mtb
Test Time Required
I. Nucleic acid amplification test detection (NAAT-TB) 1 d
II. Nucleic acid amplification test, resistance markers (NAAT-R) 1–2 d
III. Acid-fast bacilli microscopy 1 d
IV. Growth detection Up to 6–8 wk
Liquid (average 10–14 d)
Solid (average 3–4 wk)
V. Identification of Mtb complex by DNA probe or high-
performance liquid chromatography (HPLC).
1 d
a
VI. First-line drug susceptibility testing (liquid medium)
1–2 wk
a
VII. Second-line and novel compound drug susceptibility testing
Liquid
1–2 wk
a
Solid
3–4 wk
a
a
Aer detection of growth
S, strong ; C, conditional; H, high; M, moderate; L, low; VL, very low quality of evidence
