CRP and Cyanosis: Children from whom NPA were available for RT–PCR testing compared to those in whom samples were unavailable were older (median age: 10 vs. 8 months; p<0.001), were 1.3-fold less likely to have tested positive for one of the previously-tested respiratory viruses (33.3% vs. 42.3%; p<0.001), had a higher prevalence of cyanosis (11.4% vs. 8.1%; p = 0.025), higher evidence of CXR-AC (26.6% vs. 22.1%; p = 0.041), higher C-reactive protein (CRP) levels (median: 15 vs. 12 mg/l; p = 0.003) and higher procalcitonin (PCT) concentration (median: 0.26 vs. 0.15 ng/ml; p = 0.006); Table S2.