Chronic Q-fever patients detected at any time during the four-year follow-up period according to the Dutch Q-fever Consensus Group classification [16] based on IgG phase I ≥1:1,024 (n = 58).

a The Dutch Q-fever Consensus Group classification [16] was not established yet at twelve-month follow-up, and IgG phase I ≥1:2,048 was used at that time to diagnose chronic Q-fever. For this table, we applied the criteria of the Dutch Q-fever Consensus Group (IgG phase I ≥1:1,024) to the data.
b These participants did not meet the criteria of the Dutch Q-fever Consensus Group [16] at twelve months: one possible chronic Q-fever patient had an IgG phase I titre of 1:128 at month twelve, the remaining five had a titre of 1:512 (Table 3).
c This patient did not have fever, pneumonia, or hepatitis at time of the primary C. burnetii infection.
d These patients are included in the number of chronic Q-fever cases identified within the first year.
e One possible to proven (at time of visiting the outpatient clinic for our study the newly obtained serum sample was C. burnetii PCR positive), and one probable to proven (despite serological and clinical follow-up later than twelve months after diagnosis, the probable chronic infection progressed to a proven Q-fever endocarditis that was detected based on our follow-up study).
f One possible to probable (valvulopathy not meeting the modified Duke criteria [17]).
g Two possible chronic Q-fever patients (identified at month twelve) were referred to the outpatient clinic at four-year follow-up, but no progression occurred.
Chronic Q-fever patients detected at any time during the four-year follow-up period according to the Dutch Q-fever Consensus Group classification [16] based on IgG phase I ≥1:1,024 (n = 58).