The optimal time to start HAART in TB/HIV patients is not known. Physicians have to balance the risk of HIV progression if HAART is delayed against the risk of having to discontinue therapies because of toxicities, side effects, paradoxical reactions or unforeseen drug/drug interactions if HAART is started.   Similar routes of metabolism and elimination and extensive drug interactions may result in sub-therapeutic plasma levels of antiretroviral agents and furthermore, overlapping toxicity profiles may result in the interruption or alteration of TB and HIV regimens with potential subsequent microbiological or virological failure.  In co-infected patients delayingthe start of HAART can simplify patient management, limit the development of side effects and drug interactions and the risk of immune restorationreactions.

Deaths in the first month of TB treatment may be due to TB, while late deaths in co-infected persons are attributable to HIV disease progression.  ^68-70

Patients with HIV disease and a CD4 cell count  >200 cells/uL have a lowrisk of HIV disease progression or death during the subsequent 6 months of tuberculosistreatment. They should have their CD4 cellcount, monitored regularly and antiretroviral therapy withheld if possible during the short coursetuberculosistreatment.

Most patients with tuberculosis in the UK present with a low CD4 count, often <100 cells/uL. Some recommend that antiretroviral therapy be delayed until the first 2 monthsof tuberculosis therapy has been completed. Others would only recommend this strategy for those with CD4 counts >100 cells/uL, because of the short-term risk of developing further AIDS defining events and death^71-75

One retrospective study has shown that starting HAART early in severely immunosuppressed HIV positive patients presenting with TB is associated with decreased mortality and a lowering of the rates of progression. ⁵⁷Prospective data on these patients are needed.

8.1 Suggested timing of HAART in HIV/TB co-infection [AII]

CD4 count cells/uL	to treat with HAART
<100	As soon as possible-dependent on physician assessment, [Some physicians delay up to 2 months]
100-200	After 2 months of TB treatment
>200	After completing 6 months TB treatment*

NB:  regular 6-8 weekly CD4 count monitoring should be performed. If the CD4 count falls patient may need to start HAART.

* as per BHIVA treatment guidelines