Objectives To validate the objective criteria in the Department of Health Adult Swine Flu Assessment Tool against proxy datasets for pandemic influenza.

Design Comparative validation study with 3 datasets.

Setting Urban Emergency Department (group 1) and prehospital care (groups 2 and 3).

Participants Adults with community-acquired pneumonia (group 1, n=281), shortness of breath (group 2, n=211) or any respiratory diagnosis (group 3, n=300).

Outcome measures Hospital admission (group 1), hospital admission or intravenous therapy (group 2) and transfer to emergency department (group 3).

Results Sensitivity and specificity of the tool were 0.73 (95% CI 0.67 to 0.8) and 0.83 (0.72 to 0.9) in group 1, 0.64 (0.55 to 0.71) and 0.63 (0.52 to 0.73) in group 2 and 0.84 (0.75 to 0.9) and 0.55 (0.48 to 0.62) in group 3. Analysis of individual components of the tool and a summative score is presented.

Conclusions The objective criteria of the proposed DH assessment tool do not perform particularly well in predicting relevant clinical outcomes in feasible proxy conditions for pandemic influenza.