The "first in class" product for this class is the GenoScholar PZA-TB (Nipro, Osaka, Japan) for the detection of resistance to PZA. The GenoScholar PZA-TB test is based on the same principle as the FL-LPA and SL-LPA but requires the use of a large number of hybridization probes to cover the full pncA gene (>700 base pairs [bp]). Reading the hybridization results on the crowded strips with a total of 48 probes requires careful attention to avoid errors. However, it provides faster results than phenotypic DST and is based on molecular detection. The overall pooled sensitivity for the detection of PZA resistance was 81.2% (95% CI: 75.4-85.8%) and the pooled specificity was 97.8% (95% CI: 96.5-98.6%) (5).¹⁸ The hybridization can be performed on the TwinCubator instruments (Hain Lifescience, Germany) that are used for LPAs (16). An information sheet summarizing high complexity reverse hybridization NAATs is at Appendix 2.
WHO recommends the use of high complexity reverse hybridization NAATs in the following situations (5):
- In people with bacteriologically confirmed TB, high complexity reverse hybridization NAATs may be used on M. tuberculosis culture isolates for detection of PZA resistance, rather than culture-based phenotypic DST.
- The recommendation only applies to culture isolates; thus, this test is appropriate for use only where culture facilities are available.