• Epidemiological Risk Factors and Immunological Mechanisms of Hypersensitivity Reactions to Abacavir (Poster 621)
  Authored by P. J. Easterbrook, D. King, A. Waters, N. Ives, A. Vyakarnam, C. Taylor, and D. Thorburn
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• Comparison of Symptoms of Influenza A Infection with Abacavir-Associated Hypersensitivity Reaction (Poster 622)
  Authored by P. Keiser, C. Andrews, B. Yazdani, A. White, S. Hetherington, and D. Skiest
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Am I sick from a bug or a drug? Several posters addressed important questions relating to how to optimally recognize the hypersensitivity reaction (HSR) due to abacavir (Ziagen). P. J. Esterbrook and colleagues performed a case-control study comparing 32 persons with 35 control patients also taking abacavir (abstract 621). Features of the hypersensitivity reaction included mean onset time = 12.5 days (range 1-63) with the most common symptoms being fever (72%), rash (66%), malaise (66%), and GI symptoms (50%).

A laboratory feature distinguishing the hypersensitivity reaction group was more advanced HIV disease, statistically significant only for higher viral level at initiation of therapy. In a multivariate analysis, only white race remained statistically associated with the development of hypersensitivity reaction (p=0.026) but the authors caution that there may have been a selection bias given that 28/32 of the hypersensitivity reaction cases were white. They also performed a number of immunologic studies and found that cases tended to produce more IL-4 without an increase in IFN-gamma suggesting a shift toward type 2 immune response. Further studies to explore that observation are planned.

Phil Keiser and colleagues performed a study comparing the symptoms of influenza A to hypersensitivity reaction (abstract 622). Since hypersensitivity reaction to abacavir occurs in about 4% of patients starting that drug, and 20% of hypersensitivity reaction cases involve upper respiratory tract symptoms (cough, pharyngitis, and shortness of breath, this is a very practical issue. Fifteen cases of hypersensitivity reaction were compared to 30 cases of influenza A observed in HIV-positive patients seen at the Parkland HIV Clinic. There were no differences in temperature, CD4 counts, HIV RNA levels, or WBC. A multivariate analysis found that GI symptoms (odds ratio 8.7) and a rash (odds ratio 16.9) were more markedly more common in persons with hypersensitivity reaction. Respiratory symptoms were significantly more common in patients with influenza A. Demographic factors were not associated with hypersensitivity reaction. The take-home lesson was that respiratory symptoms with GI symptoms was more likely due to hypersensitivity reaction, while cough without GI symptoms was most likely influenza.