FeedbackAt the peripheral level (Level I), laboratories offer a range of basic diagnostic tests, with the focus being on providing initial testing to rapidly detect TB (and RIF resistance):
- The LF-LAM is the only instrument-free, POC, lateral flow TB test that delivers results within 25–30 minutes and is suitable for use in the clinic. Thus, antiretroviral therapy initiation sites or similar care centres for people living with HIV would be examples of appropriate placement sites. The test is recommended for use concurrently with an LC-aNAAT among adults, adolescents and children living with HIV. Therefore, the collection of sputum and stool must also be performed, and the samples sent for testing with an LC-aNAAT.
- LC-aNAATs are suitable for decentralized laboratory placement, offering the advantage of sensitive TB detection with simultaneous or reflex-based drug-resistance testing at the same site. Prior or existing smear microscopy sites are suitable for LC-aNAAT placement because the population served is the same and the infrastructure requirements are similar.
- Battery operated LC-aNAATs (e.g. Truenat assays) may be useful at sites where the power supply is unstable (61).
- LC-aNAATs for follow-on testing of samples from patients confirmed as having TB and RIF resistance may also be done onsite to speed up the availability of resistance results for INH, FQ, ETO and AMK without sample referral. However, the current within-class test, Xpert MTB/XDR, requires a different type of GeneXpert module (10-colour) than the Xpert Ultra test (6-colour). Given that the number of tests needed over a certain period will be much lower than the number for initial TB diagnosis, programmes can decide to replace one or more 6-colour module(s) with one or more 10-colour module(s) in existing GeneXpert instruments, to avoid replacing fully functional instruments. Furthermore, because the test has important value in providing rapid results for the management of MDR/RR-TB, sites where drug resistance is more prevalent or treatment is delivered may be prioritized for Xpert MTB/XDR testing.
- The LC-mNAAT (TB-LAMP) is also suitable for placement at the peripheral laboratory level. This class is less automated and has more testing steps than LC-aNAATs, but is also cheaper than LC-aNAATs and provides results where power supplies may vary or can be boosted with solar panels (62). However, because it does not detect RIF resistance, an alternative test or a sample referral mechanism should be considered in populations who are at high risk of MDR-TB and in settings with moderate-to-high or unknown pretest probability of DR-TB, particularly where follow-on testing for RIF resistance is not accessible or available.
- TB infection skin tests can be used in peripheral settings owing to their simple procedures. Taking the incubation period and the need for a follow-up visit into consideration, it is preferable to provide access to the test as close to the target population as possible. It is important to ensure that storage possibilities (2–8 °C) are available for the TST or TBST, and that staff are adequately trained in administering the test and reading the results.