TABLE 1.
IFA titers and clinical characteristics for patients who seroconverted to R. rickettsii, R. parkeri, and/or R. amblyommii antigensa
| Patient no. (n = 21) | IFA titer (acute, convalescent phase) |
Presumptive agent by: |
Symptom(s) |
Hospitalized | Discharge diagnosis | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| R. rickettsii | R. parkeri | R. amblyommii | Cross-absorption with IFA | Western blot | Fever | Rash | Headache | Myalgia | Other | |||
| Patients who seroconverted to all 3 antigens | ||||||||||||
| 3 | <1:64, 1:256 | <1:64, 1:1,024 | <1:64, 1:512 | R. parkeri | IND | + | + | − | − | − | − | Presumed RMSF |
| 42 | 1:128, 1:1,024 | 1:512, >1:2,048 | 1:128, >1:2048 | R. parkeri | R. parkeri | + | − | − | + | Leukopenia | − | NA |
| 56 | <1:64, 1:512 | <1:64, ≥1:2,048 | <1:64, ≥1:2,048 | R. rickettsii | IND | + | + | + | + | Lethargy, thrombocytopenia | − | RMSF |
| 58 | <1:64, 1:1,024 | <1:64, 1:512 | 1:64, 1:512 | R. rickettsii | IND | + | − | + | + | Nausea, vomiting | Febrile illness, possible RMSF | |
| 65 | <1:64, 1:512 | <1:64, 1:256 | <1:64, 1:256 | NA | NA | NA | NA | NA | NA | NA | ||
| 68 | <1:64, 1:2,048 | <1:64, ≥1:2,048 | <1:64, 1:2,048 | IND | IND | − | + | − | − | Cough | − | Rash, unspecified |
| 85 | <1:64, 1:2,048 | 1:64, 1:1,024 | 1:64, 1:1,024 | NA | NA | NA | NA | NA | NA | NA | ||
| Patients who seroconverted to 2 antigens | ||||||||||||
| 55 | 1:64, 1:64 | 1:256, 1:1,024 | 1:256, 1:2,048 | NA | NA | NA | NA | NA | NA | NA | ||
| 88 | 1:512, 1:256 | 1:1,024, 1:256 | 1:1,024, 1:256 | R. amblyommii | IND | + | − | + | + | Multipleb | − | NA |
| 109 | 1:256, 1:128 | 1:256, 1:1,024 | 1:256, 1:1,024 | + | − | NA | NA | NA | − | NA | ||
| Patients who seroconverted to 1 antigen | ||||||||||||
| 5 | 1:128, 1:64 | 1:64, 1:64 | 1:64, 1:256 | NA | NA | NA | NA | NA | NA | NA | ||
| 7 | 1:256, 1:256 | 1:256, <1:64 | 1:128, <1:64 | NA | NA | NA | NA | NA | NA | NA | ||
| 19 | 1:512, 1:512 | ≥1:2,048, 1:1,024 | 1:2,048, 1:512 | NA | NA | NA | NA | NA | NA | NA | ||
| 25 | 1:128, 1:1,024 | 1:256, 1:256 | 1:1,024, ≥1:2,048 | NA | NA | NA | NA | NA | NA | NA | ||
| 29 | 1:64, 1:128 | 1:128, 1:512 | 1:128, 1:256 | NA | NA | NA | NA | NA | NA | NA | ||
| 31c | 1:128, 1:256 | 1:256, 1:256 | 1:256, 1:1,024 | + | − | − | − | Multipled | + | Tick-borne illness | ||
| 44 | 1:128, 1:256 | 1:512, 1:1,024 | 1:64, 1:512 | NA | NA | NA | NA | NA | − | NA | ||
| 70 | 1:256, 1:256 | 1:256, 1:1,024 | 1:256, 1:256 | IND | IND | + | − | + | + | Multiplee | + | NA |
| 76 | 1:512, 1:256 | 1:1,024, 1:2,048 | 1:512, 1:2,048 | − | − | − | + | Fatigue | − | NA | ||
| 93 | 1:512, 1:512 | 1:2,048, 1:512 | 1:1,024, 1:1,024 | − | − | − | − | − | − | NA | ||
| 116 | 1:128, 1:128 | 1:128, 1:64 | 1:512, 1:128 | NA | NA | NA | NA | NA | NA | NA | ||
Seroconversions are highlighted in bold. For subjects with sufficient remaining sera, the presumptive agent was determined from the results of cross-absorption of convalescent-phase sera followed by IFA and/or Western blotting. IND, indeterminate; NA, not available; +, positive; −, negative.
Nausea, diarrhea, weakness, cough, and sweats.
In the original testing, this patient seroconverted to E. chaffeensis with acute- and convalescent-phase titers of 1:128 and 1:8,192.
Elevated liver enzymes, acute renal failure, thrombocytopenia, leukopenia, and anemia.
Elevated liver enzymes, thrombocytopenia, leukopenia, and anemia.