ICAAC: TB patients with good CD4 cell counts can safely defer HIV treatment

HIV-positive individuals who develop tuberculosis (TB) whilst they still have a CD4 cell count above 250 cells/mm³ can defer the initiation of antiretroviral therapy without risking the development of additional AIDS-defining illness or a drop in their CD4 cell count, according to a French study presented to the 45^th Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington DC last month.

Tuberculosis has been considered an AIDS-defining illness since the early 1990s, but unlike other AIDS-defining conditions which typically only occur when an individual has a CD4 cell count below 200 cells/mm³, tuberculosis can occur in HIV-positive patients who have only modest immune suppression.

Antiretroviral treatment guidelines generally recommend that individuals who are ill because of HIV initiate antiretroviral therapy. There are however interactions between anti-HIV drugs and some medicines used to treat tuberculosis which mean that patients who need to start anti-HIV therapy may have to wait for two months after completing their six month course of tuberculosis treatment before initiating antiretroviral therapy.

But do all HIV-positive patients with tuberculosis need to start anti-HIV treatment in the short to medium term?

To answer this, investigators from Paris, France, conducted a retrospective analysis of all cases of tuberculosis diagnosed in HIV-infected patients between 2000 and 2004.

A total of 93 cases were seen in 87 patients, 58 were men, and the majority were from areas with a high incidence of tuberculosis (58 patients were from sub-Saharan Africa and six were north African).

The investigators divided the patients into two groups on the basis of their baseline CD4 cell count. Group one included 25 patients who had a CD4 cell count above 250 cells/mm³ (median 442 cells/mm³) and therefore did not, on the basis of many current treatment guidelines, need to initiate anti-HIV therapy immediately. At baseline, 13 of these patients were naive to antiretroviral therapy. The second group included the remaining 68 cases involving individuals with a CD4 cell count below 250 cells/mm³ (median 77 cells/mm³). At the time when tuberculosis was first diagnosed, 41 of these individuals were naive to anti-HIV drugs.

A total of seven patients died, all but one having a baseline CD4 cell count below 250 cells/mm³. The cause of death was directly related to tuberculosis in two patients.

Following tuberculosis therapy, anti-HIV drugs were prescribed to 15 patients in group one and 74 individuals in group two. After twelve months, median CD4 cell count increased to 506 cells/mm³ amongst the patients with higher CD4 cell counts (a non-significant increase from baseline, p = 0.1) and to 201 cells/mm³ amongst the group of patients with more advanced immune suppression (a highly significant increase, p < 0.001).

A total of 15 patients in group one who did not have immune suppression either did not start or interrupted anti-HIV therapy. After twelve months, none of these patients had experienced a new AIDS-defining event and the median CD4 cell count had remained stable and well above the level where they were at a significant risk of further disease progression.

The investigators draw a number of conclusions from their study.

• Over a quarter of cases of tuberculosis occurred in patients with a good CD4 cell count.
• The clinical course of tuberculosis and a patient’s prognosis was determined by their CD4 cell count.
• Although tuberculosis is an AIDS-defining event, it may not be necessary to initiate antiretroviral therapy in patients who are not immunocompromised at the time of their tuberculosis diagnosis.