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Table 3 Clinical, Temporal and Testing Characteristics Associated with PCR-Positive, Culture-Negative Specimens (N = 1858), 1999-2005

From: Pertussis resurgence in Toronto, Canada: a population-based study including test-incidence feedback modeling

Specimen Characteristic Odds Ratio 95%   CI P-value
Age 0-4 2.61 1.71 To 3.98 < 0.001
Age 5-9 1.73 1.02 To 2.93 0.04
Age 10-14 0.41 0.25 To 0.65 < 0.001
Age 15-19 0.41 0.20 To 0.82 0.01
Age > 20 (referent) 1.00 --- --- --- ---
Time (years) 1.13 1.03 To 1.25 0.01
Introduction of Novel PCR (May 2005) 16.35 10.19 To 26.23 < 0.001
  1. NOTE: Model also included sine and cosine terms to adjust for residual confounding by season (see text). CI, confidence interval.