Volume 25, Number 5—May 2019
Value of PCR, Serology, and Blood Smears for Human Granulocytic Anaplasmosis Diagnosis, France
|Test result||Control group, no./total||Anaplasma group, no./total|
|Positive blood smear
|Positive by serology||2/36||16/19|
|Seroconversion* or 4-fold rise in antibody titer||1/36†||6/19‡§|
|Antibody titer >1:256 at first
*Seroconversion is defined as a change in antibody titer from negative in the first sample obtained during acute illness to >1/64 in the second sample acquired >4 weeks later.
†One patient had a seroconversion with a microbiologically confirmed diagnosis of parvovirus B19 infection.
‡Only 1 patient had a 4-fold increase in antibody titer, but the titer at the first study visit was already high enough to establish the diagnosis (increase from 1:512 to 1:2,048).
§One patient had a seroconversion with an A. phagocytophilum antibody titer >1:256 at the second visit (patient counted once in both serology categories). All other patients with seroconversion had an antibody titer <1:256.
¶One patient with microbiologically confirmed leptospirosis had an A. phagocytophilum antibody titer of 1:256 at the first visit that decreased to 1:64 at the second visit.