Table 4.

Bivariate linear regression analysis between Cq and the additional covariates, excluding log₁₀ genomes/ml^a

Covariate	z value	P value
Sample vol	−2.27	0.023
DNA extraction system
Roche	−0.11	0.909
Qiagen	−1.15	0.250
Other	1.50	0.133
Elution vol	2.96	0.003
PCR amplification system
Roche	−0.64	0.521
ABI	0.53	0.598
Other	0.25	0.803
Template vol	−1.07	0.286
PCR vol	0.97	0.334
PCR target
18S rRNA gene	−0.28	0.779
ITS region	−2.48	0.013
28S rRNA gene	0.39	0.698
Mitochondrial	2.57	0.010
Internal control	−2.18	0.029

^aSignificant associations are highlighted in boldface. Note that a negative z value predicts an earlier Cq, and thus a higher probability of PCR positivity, whereas a positive value has the opposite effect.