Response to treatment is monitored on the basis of monthly sputum smear microscopy, as well as culture, ideally at the same frequency. Monthly culture increased the detection of patients with a true positive bacteriological result when compared with sputum smear microscopy alone; also, it reduced the proportion of patients with a false negative result.
Concomitant use of sputum smear microscopy and culture test results helps to identify patients whose bacteriology remains positive or reverts to positive following initial conversion to negative. This combined testing will help clinicians to identify patients whose treatment is likely to fail, and thus to plan alternative options and institute infection control measures in a timely manner. Additional benefits would be expected from reduced transmission and development of resistance, and from appropriate changes to treatment regimens. Regular microscopy and culture of sputum or other specimens remain important to ensure that treatment failure is detected early. The frequency of these examinations is similar to the schedule used in patients on the 9-month all-oral MDR-TB regimen and the BPaLM/BPaL regimen.
The treatment outcome definitions and reporting framework for patients on longer regimens are the same as those for patients on other MDR-TB regimens (38). The updated definition of treatment failure includes situations where a patient’s treatment regimen has been terminated or permanently changed to a new treatment regimen, owing to:
- no clinical or bacteriological response to treatment;
- adverse drug reaction; and
- evidence of additional drug resistance to medicines in the regimen.
Bacteriological failure is considered when patients treated with a longer regimen remain positive without conversion, or revert to positive following initial conversion to negative.
Failure due to adverse drug reactions or drug resistance is considered when additional resistance emerges while the patient is on a longer regimen, or the regimen needs to be stopped because of a severe adverse event.
In children, smear and culture monitoring of the response to treatment may be challenging, for the same reasons that make it difficult to obtain a bacteriological confirmation of the diagnosis. In children with a bacteriologically confirmed diagnosis, all reasonable efforts should be taken to demonstrate bacteriological conversion. In children in whom cultures have become negative or who never had a confirmed diagnosis, repeated respiratory sampling may not be useful if the child is otherwise responding well clinically. Resolution of clinical symptoms and weight gain can be used as indicators of improvement. All children should have regular clinical follow-up, including weight and height monitoring. Drug dosages should be adjusted with weight gain, as needed (47).