TABLE 2.
Rifampicin test results of TLA and Xpert MTB/RIF against composite reference standard
| RMP result by CRSa | No. of isolates | rpoB target (Sanger sequencing/WGS) | Results of: |
LJ-MIC (μg/ml) | MGIT DST | TLA final interpretation | TLA-Xpert concordance | |||
|---|---|---|---|---|---|---|---|---|---|---|
| LJ | Xpert | TLA RMP DST | MTBDRplus | |||||||
| RMP-R (n = 28) | 1 | M434I, I491F/M434I, I491Fc | R | R | R | na | na | na | True RR | Concordant |
| 3 | na/H445L | R | R | R | na | na | na | True RR | Concordant | |
| 8 | na/S450L | R | R | R | na | na | na | True RR | Concordant | |
| 2 | WT/WTd | R | R | R | na | na | na | True RR | Concordant | |
| 1 | H445D/H445D | R | Neg | R | na | na | na | True RR | na | |
| 1 | I491F, S450L, M434I/I491F, S450L, M434Ic | R | Neg | R | na | na | na | True RR | na | |
| 1 | I491F/I491Fc | R | IND | R | na | na | na | True RR | na | |
| 1 | S450L/S450L | R | na | R | na | na | na | True RR | na | |
| 5 | I491F/I491F | R | S | R | WT | 160 to >320b | 3S, 2R | True RR | Discordant | |
| 1 | H445L, WT/WTf | R | S | R | WT | 160 | S | True RR | Discordant | |
| 1 | V170F/V170F | R | S | R | WT | 160 | R | True RR | Discordant | |
| 1 | WT/WTe | R | S | R | WT | 160 | R | True RR | Discordant | |
| 1 | S450L/S450L | R | R | S | delWT, MUT3 | 160 | R | False RS | Discordant | |
| 1 | WT/WTe | R | S | S | WT | 160 | R | False RS | Concordant | |
| RMP-S (n = 168) | 99 | na/WT | S | S | S | na | na | na | True RS | Concordant |
| 6 | WT/nd | S | S | S | na | na | na | True RS | Concordant | |
| 36 | na/na | S | S | S | na | na | na | True RS | Concordant | |
| 24 | na/na | S | na | S | na | na | na | True RS | na | |
| 1 | WT/WT | S | R | S | WT | 20 | S | True RS | Discordant | |
| 1 | WT/WT | R | S | S | WT | 20 | S | True RS | Concordant | |
| 1 | WT/WT | S | S | R | WT | 20 | S | False RR | Discordant | |
a
CRS, composite reference standard; WGS, whole-genome sequencing; Xpert, Xpert MTB/RIF; LJ, Löwenstein-Jensen media; TLA, thin-layer agar; RMP, rifampicin; MGIT, mycobacterial growth indicator tube; na, not available; IND, RMP indeterminate; Neg, negative; nd, not determined.
b
One result invalid.
c
Isolates with I491F mutations either detected also by Xpert or without Xpert result.
d
Paired isolates with rpoB sequencing WT results.
e
P631S mutation in the ponA1 region.
f
rpoB H445L plus L452P detected at low-frequency mode.