Table 4.

Spearman rank correlation coefficients for mean C_T values for duplicate Coxiella burnetii real-time PCR tests in relation to age, number of days after illness onset, and IgG phase I titers 12 months after diagnosis

Parameter analyzed	No. of patients	Spearman rank correlation coefficient (rs)a	Pb
Age	366	−0.005	0.924
Days after illness onset	249	0.232	<0.001
IgG phase I titer 12 mo after diagnosis	312	−0.338	<0.001

^aSpearman rank correlation coefficient for the relationship between C_T values and the parameter indicated.

^bTwo-tailed test.