Syndromic surveillance for influenza in two hospital emergency departments. Relationships between ICD-10 codes and notified cases, before and during a pandemic

Table 4 Top correlations calculated between ICD-10 coded cases and NIDS cases after excluding the 2009 influenza season

ICD-10 Code	Description	All data		Postcode restricted
		Correlation	p	Correlation	p
J11	Influenza virus not identified	0.433	< 0.0001	0.368	< 0.0001
J06	Acute upper respiratory infection multiple and unspecified sites	0.433	< 0.0001	0.409	< 0.0001
J22	Unspecified acute lower respiratory infection	0.424	< 0.0001	0.387	< 0.0001
B34	Viral infection, unspecified site	0.356	< 0.0001	0.365	< 0.0001
J18	Pneumonia organism unspecified	0.304	< 0.0001	0.262	< 0.0001
'Best' codes combined (r_s >0.3)		0.529	< 0.0001	0.526	< 0.0001

ISSN: 1471-2458