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Standard First Regimens Less Effective in US Blacks Than Others
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17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
African Americans had about a twice higher chance of reaching a viral load below 400 copies than of changing their first regimen within 48 weeks of starting, according to results of a 1000-person study [1]. But that "effectiveness" rate compared poorly with other groups analyzed, who had a 3 times higher chance of reaching an undetectable load than of changing their first regimen.
This CNICS cohort analysis involved 1048 adults starting their first antiretroviral regimen with efavirenz, lopinavir/ritonavir, or atazanavir/ritonavir paired with tenofovir/emtricitabine (TDF/FTC) or abacavir/lamivudine (ABC/3TC) from August 2004 through December 2008 at seven CNICS clinics. The investigators measured effectiveness by the adverse benefit ratio, defined as the cumulative incidence of regimen change or discontinuation compared with virologic suppression. A lower adverse benefit ratio signals a more effective regimen. A ratio below 1.0 indicates a greater probability of pushing the viral load below 400 copies before changing or stopping a drug.
The highest proportion of study participants, 56%, began an efavirenz regimen, followed by atazanavir/ritonavir (36%) and lopinavir/ritonavir (8%). Most study participants, 85%, were men, 29% were African American, 26% had an AIDS diagnosis, and 13% became infected through needle sharing. Median age for the group stood at 38 years (interquartile range 32 to 45). While 42% of cohort members started therapy with a CD4 count under 200, 36% started with 200 to 349 CD4s and 23% with 350 or more.
After 48 weeks, 54% of study participants had changed their regimen and 74% had a viral load under 400 copies. Neither time to virologic suppression nor time to regimen change differed significantly among the three regimens studied. Adverse benefit ratios (defined above) at 48 weeks were similar for efavirenz (0.37), atazanavir/ritonavir (0.42), and lopinavir/ritonavir (0.39), a result indicating that most people taking any of these regimens as first-line therapy were more likely to reach a sub-400 viral load than to stop or switch antiretrovirals in 48 weeks.
Among the 309 African Americans studied, 176 (57%) changed or discontinued their regimen within 48 weeks, whereas 133 (43%) did not. While 206 African Americans (67%) reached a viral load below 400 copies, 103 (33%) did not. African Americans had an adverse benefit ratio of 0.52, compared with a better ratio of 0.35 for other groups, a significant difference (P = 0.002).
Statistical analysis that considered sociologic, demographic, and clinical factors determined that African Americans were 1.9 times more likely to reach a viral load below 400 than to stop or change antiretrovirals within 48 weeks, while other groups were 2.9 times more likely to attain an undetectable load than to stop or switch. By this measure, standard first-line regimens were less effective in African Americans than in other groups.
The findings confirm other studies showing a worse response to antiretrovirals in US blacks than in nonblack groups. The investigators do not speculate on the reasons for this difference, although psychosocial factors are probably involved. This analysis did not measure adherence to gauge its impact on antiretroviral discontinuation and virologic response.
Reference
1. Mugavero M, Lau B, Crane H, et al. Relative effectiveness of preferred initial antiretroviral regimens in the CFAR network of integrated clinical systems cohort. 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 508. http://www.retroconference.org/2010/PDFs/508.pdf
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