The diagnosis of pandemic influenza is clinical. This prospective study questions the validity of the Department of Health guidelines in 77 children admitted to hospital. The positive predictive value for the guidelines was 0.39. Although H1N1 was identified in a sizeable minority of cases using the guidelines, virology testing is still required.
Smith, H., Raju, V., Turner, S., & Oxley, C. (2011). Are the UK clinical guidelines for H1N1 influenza infection valid in the hospital setting? Archives of Disease in Childhood, 96(9), 857-859. https://doi.org/10.1136/adc.2010.182857