The dramatic spread of the HIV epidemic throughout sub-Saharan Africa in the past decades has been accompanied by up to a fivefold increase in the number of TB cases registered by national TB programmes. There is thus a need for strong collaboration between HIV/AIDS and TB programmes. Therefore strategies to control HIV must also include interventions to control TB.
TB preventive therapy is the use of one or more anti-tuberculosis drugs given to individuals with latent infection with M. tuberculosis in order to prevent progression to active TB disease. Trials have shown that maximum benefits from TB preventive therapy are achieved in HIV infected patients with evidence of tuberculosis infection as assessed by a positive tuberculin skin test. In these patients, the risk of developing tuberculosis is reduced by about 60% and their survival is also prolonged. However, some benefit is also shown in HIV positive groups in general, regardless of the tuberculin test result.
TB preventive therapy is an intervention that should be part of the package of care for people living with HIV. However it should only be offered in the following situations (prerequisites):
Availability of quality voluntary counselling and rapid testing for HIV
Effective screening for active TB before initiating TB preventive therapy
Capacity for follow up and monitoring of patients to encourage adherence to preventive therapy in order to address eventual side effects and exclude active TB disease
The local HIV Programme must take responsibility for implementation of preventive therapy
Table 11: Strategies to Exclude Active Tuberculosis before initiating Isoniazid Preventive Therapy (IPT)
It is essential to exclude active tuberculosis in every patient prior to starting preventive therapy. This is critical in order to the development avoid drug resistance when drugs are given to patients with TB disease who require the full regimen. See Chapter 13 for more details
Symptoms and signs to be noted
Patients on TB preventive therapy should be specifically asked about signs and symptoms of tuberculosis:
• Cough > 2 weeks
• Fever > 2 weeks
• Night sweats
• Weight loss of > 1.5 kg in the past 4 weeks
• Pleuritic chest pains and haemoptysis
• Other symptoms suggesting extrapulmonary TB
Investigations to be done
All patients with 1 or more signs and symptoms must be investigated further for TB and are not immediately eligible for TB preventive therapy: 3 sputum specimens must be collected for the following investigations:
• 2 sputum samples for microscopy
• 1 sputum for culture
Chest x ray is recommended in the screening for TB Preventive therapy, and has an important role in those who are TB suspects with negative sputum smears as per the national TB guidelines.
Eligibility for TB Preventive Therapy
All HIV positive people with no signs and symptoms suggestive of active TB and with positive tuberculin skin test are eligible for TB preventive therapy
Tuberculin skin test should be offered to all HIV infected individuals where possible. Staff should be trained to provide quality tuberculin skin test using the Mantoux technique.
For patients with history of TB treatment:
Patients who had active tuberculosis in the past 2 years should not be considered for preventive therapy.
Patients who were treated for tuberculosis more than 2 years earlier may be considered because they may have already been re-infected with TB.
Patients on anti-retroviral therapy should not be offered TB preventive therapy, as there is currently no evidence of added benefit.
Patients who receive TB preventive therapy and who require to start antiretroviral therapy can complete their TB preventive therapy even if the ART is started as there is no interaction between isoniazid and the current ART regimen used.
The standard regimen for TB preventive therapy is: Isoniazid (INH) daily 5 mg/kg/day (maximum 300 mg per day). The recommended duration is: 6 months
At this stage the intervention should be given once only and the protective effect is expected to last for 18 months.