Comparison of covariate adjustment methods using space-time scan statistics for food animal syndromic surveillance

Table 1 Results of the space-time scan statistic using “parasitic liver” condemnation data

Date of cluster	No. of abattoirs in cluster	Latitude (°N)	Longitude (°W)	Radius (Km)	No. of cases	Relative risk¹	P-value
a) Unadjusted Poisson space-time scan test
Jul 2004 - Dec 2007	16	44.52	80.92	62.45	12907	3.66	< 0.001
Mar 2002 - Aug 2005	26	43.60	79.81	62.52	6385	0.36	< 0.001
b) Animal-adjusted Poisson space-time scan test
Dec 2006 - Dec 2007	14	44.53	80.99	52.98	4973	3.90	< 0.001
Dec 2001 - May 2005	51	42.91	79.50	117.97	8732	0.45	< 0.001
Aug 2003 - Jan 2007	69	44.36	76.35	255.37	13849	1.59	< 0.001
c) Model-adjusted space-time scan test
Mar 2001 - Jun 2002	1	43.90	81.31	0	420	4.91	< 0.001
Sep 2003 - May 2004	71	43.18	80.51	98.22	4576	1.52	< 0.001
Sep 2001 - Dec 2001	16	43.33	79.98	46.01	1335	2.19	< 0.001
Mar 2004 - Nov 2006	2	44.11	80.80	0	2338	0.62	< 0.001
Jan 2001 - Mar 2001	72	44.40	77.61	197.95	496	0.49	< 0.001
Mar 2005 - Jan 2006	1	44.36	76.35	0	56	0.18	< 0.001
d) Space-time permutation scan test
Jan 2001 - Sep 2002	2	43.65	79.86	4	2335	6.76	< 0.001
Jan 2001 - Sep 2003	7	44.13	80.61	29.42	341	0.11	< 0.001
Sec 2006 - Dec 2007	2	44.11	80.80	0	4431	3.06	< 0.001
e) Space-time scan test of residuals
No statistically significant clusters found

¹The values in this column for the space-time permutation model refer to the observed/expected value.

ISSN: 1746-6148