Suggested evaluation prior to and during TPT are outlined below. Although differing follow-up strategies have not been compared in RCTs, these recommendations are based on the protocols of large RCTs in which moderate rates of adverse events have been observed.7,21
It is critical to exclude active TB prior to initiation of TPT in order to avoid undertreatment of TB disease, with subsequent development of drug resistance. At a minimum, the initial assessment should include a clinical assessment and chest x-ray. If abnormalities are detected, then TPT should be deferred until negative mycobacterial sputum culture results have been obtained. Patients’ baseline medications should be determined and evaluation for potential drug-drug interactions between these and proposed TPT regimens examined (see drug-drug interactions section, above). Evaluation of potential risk factors and barriers for non-completion, as well as patient understanding, is also important to ensure successful completion. We suggest baseline testing for all patients undergoing TPT, including complete blood count, alanine aminotransferase, bilirubin, as well as hepatitis B and C and HIV serologies.
Prior to starting TPT (all regimens), patients should be counseled that on average 5-10% of those who are infected will develop TB during their lifetime and that half of those people will develop TB within the first two years of infection. Key risk factors could also increase the risk of reactivation considerably (see Chapter 4: Diagnosis of Tuberculosis Infection). They should be counseled that taking all doses of the TPT will reduce this risk significantly, thus preventing the development of active TB disease. Patients should also be informed about possible adverse events associated with TPT that can occur but are rare. They should be told to contact the clinic should they develop possible adverse events. If prompt evaluation of such events by a health care provider is not possible or if symptoms are severe then the patient should stop their treatment medication. The British Columbia Center for Disease Control (BCCDC) provides a website with basic information regarding latent TB infection, including patient handouts in a variety of languages.82
Evaluation during treatment
Evaluation at the end of the first month of treatment provides an opportunity to assess medication tolerability and to encourage adherence, since adherence to treatment in the first month strongly predicts treatment completion.83 In general, monthly clinical assessments should be continued for the duration of treatment. However, in patients at low risk of adverse events and likely to complete treatment, the interval between visits may be extended.
As part of evaluation after one month of treatment, ALT (a blood test for liver function) and bilirubin should be performed (all regimens). In patients on TPT regimens including a rifamycin, a complete blood count should also be performed at this time. Patients taking 4 R or 3HP do not require further laboratory monitoring during treatment unless the patient has an abnormal test result, develops symptoms suggesting an adverse event or has risk factors for hepatotoxicity (history of previous drug-induced hepatitis, current cirrhosis or chronic active hepatitis of any cause, hepatitis C, hepatitis B with abnormal transaminases). This approach is justified given that the risk of hepatotoxicity with these regimens is much lower than for isoniazid monotherapy7,21 For patients on regimens other than 3HP or 4 R, monthly monitoring of ALT and bilirubin should also be performed among patients with risk factors for hepatoxicity. In patients without such risk factors, the benefit of ALT and bilirubin monitoring is uncertain but should be considered.
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