Clinical and Laboratory Criteria:
(1) history of tick exposure
(2) nonspecific febrile illness (rigors, malaise, headache, nausea, anorexia, arthralgias) with temperature > 37.6°C
(3) nonrevealing physical examination
(4) single IFA (indirect fluorescent antibody) titer >= 1:80
(5) neutrophil morulae present (clusters of bacteria within cytoplasmic vacuoles of leukoctyes)
(6) positive PCR (using primers ge9f and ge10r)
(7) 4 fold or greater increase in IFA titer between acute and chronic convalescent phase serum sample obtained at least 2 weeks apart
(8) blood cell culture positive for Ehrlichia, using HL-60 human promyelocytes
Possible ehrlichiosis:
(a) criteria 1, 2, and 3 present
Probable ehrlichiosis:
(a) criteria 1, 2, and 3 present
(b) one or more of 4, 5 or 6
Confirmed ehrlichiosis:
(a) criteria 1, 2, and 3 present
(b) one or more of 5 + 6, 7, or 8
where:
• In Table 3, page 557, it is unclear if the "b" criteria for probable ehrlichiosis need to be tested for in confirmed ehrlichiosis. My reading is that the "b" criteria for confirmed include these items.
• Since a tick bite might not always be noticed, and since some of the tests are specific, classifying a patient missing one or more of the first 3 criteria and having one or more positive laboratory tests is not given.
|
Laboratory Test
|
Percent of Patients with Positive Test Result
|
|
morulae in blood smears
|
62%
|
|
PCR analysis
|
67%
|
|
cell culture
|
55%
|
|
IFA titer >= 80
|
99%
|
|
IFA titer increase 4 fold or greater
|
99%
|
from Table 2, page 556.
