Differentiation between abacavir hypersensitivity and viral respiratory 
infections is problematic. Fifteen cases of abacavir hypersensitivity were 
matched to 30 controls with culture proven influenza A with no abacavir 
exposure. Rash was associated with hypersensitivity (odds ratio [OR] = 13.1, P = 
0.02) as was the presence of nausea (OR = 30, P < 0.001), vomiting (OR = 17.1, P 
= 0.001) or diarrhoea (OR = 22, P < 0.001). The number of gastrointestinal 
symptoms was also predictive of hypersensitivity reaction (P < 0.001). 
Respiratory symptoms (cough, sore throat, or dyspnoea) were not associated with 
abacavir hypersensitivity (OR = 0.08, P = 0.001). Multivariate analysis 
confirmed the following associations for abacavir hypersensitivity: the number 
of gastrointestinal symptoms (OR = 8.6, P = 0.0032), cough (OR = 0.039, P = 
0.02) and rash (OR = 16.9, P = 0.07). Abacavir hypersensitivity is strongly 
associated with gastrointestinal (GI) symptoms. Cough without GI symptoms is 
associated with influenza.