Performance of the B. henselae Houston-1 IEX fraction 24 ELISA with human sera (ntotal = 79). Results of the ELISA are grouped for IFA-positive sera from patients suffering from a PCR-proven infection (n = 10), IFA-positive sera from patients with a CSD-specific medical history (n = 21), IFA-positive sera from patients without a CSD-specific clinical history (n = 12), IFA-positive sera with a low (1:320) IFA titer (n = 20), and IFA-negative (<1:80) sera (n = 16). Values above the range are set to 60 relative units (RU). Bars represent the mean value. Values above 11 RU are considered positive (black circles), and values below 9 RU are considered negative (white circles). Values between 9 and 11 RU are equivocal (white circles with an X). Respective P values between sample categories are given.