Although direct MTBDRsl testing of sputum is successful in most patients, it results in relatively high proportions of non-actionable results in smear-positives and especially in smear-negatives. MTBDRsl failed in four out of 10 smear-negative patients with Xpert-diagnosed rifampicin-resistance. As seen for MTBDRplus, a failure to generate an actionable result on smear-negatives was the primarily cause of resistance missed (as opposed to a false-negative susceptible result).
Resistance classifications on bottom two rows of boxes are per direct MTBDRsl
Of the 849 culture-positive patients only 769 had usable pDST (80-contaminated).
*Indirect smear-positive MTBDRsl results: FQ-R (n=3), SLID-R (n=0), FQ-R and SLID-R (n=0), fully susceptible (n=33), and non-actionable (n=0).
**Indirect smear-negative MTBDRsl results: FQ-R (n=7), SLID-R (n=4), FQ-R and SLID-R (n=2), fully susceptible (n=175), and non-actionable (n=0)
Abbreviations: FQ-fluoroquinolones, SLID-second line injectable drug, R-resistant, n-number, TUB-TUB-band, pDST-phenotypic drug susceptibility testing.