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Table 1 Univariable associations a between the weekly probability of PRRSV ELISA positivity at the Animal Health Laboratory from January 1, 2000 to April 30, 2007 and the PCVAD outbreak of the Ontario swine industry, a PRRSV outbreak, season, and year

From: Identifying an outbreak of a novel swine disease using test requests for porcine reproductive and respiratory syndrome as a syndromic surveillance tool

Variable n ORb 95% CI P-value
PCVAD outbreak   0.87 0.77 - 0.97 0.02
PRRSV outbreakc   1.19 1.04 - 1.37 0.01
Seasonc Fall 91 Referent - -
Spring 101 1.08 0.95 - 1.24 0.25
  Summer 91 1.05 0.91 - 1.21 0.50
Winter 99 1.05 0.92 - 1.20 0.77
Year 2000 - Referent - -
2001 52 0.89 0.72 - 1.10 0.28
2002 52 0.97 0.79 - 1.18 0.75
2003 52 0.77 0.63 - 0.94 0.01
2004 52 0.78 0.64 - 0.95 0.01
2005 52 0.60 0.49 - 0.73 <0.001
2006 52 0.37 0.31 - 0.45 <0.001
  2007 18 0.25 0.19 - 0.32 <0.001
  1. a. Logistic regression using generalized linear model ML estimation with the logit link, binomial distribution and total number of PRRSV ELISA tests ordered representing the denominator.
  2. b. Odds ratio.
  3. c. Suspected a priori may be a confounding variable.
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