- Author: Jason F Okulicz, MD, FACP, FIDSA; Chief Editor: Michael Stuart Bronze, MD more...
Laboratory studies are not particularly helpful in confirming a diagnosis of typhus. These studies assist the clinician in assessing the degree of severity of the illness and in helping exclude other diseases in the differential diagnoses.
The diagnosis of typhus is clinically suggested when the appropriate historical elements are elicited from a patient who presents with the characteristic symptoms and signs.
Antibiotic therapy should begin promptly when the diagnosis is suspected; thereafter, appropriate laboratory studies can be serially performed as needed.
Diagnosis may be confirmed using laboratory tests; however, more than one week may pass before patients mount a demonstrable immune response that can be measured serologically.
Laboratory confirmation of typhus is obtained irrespective of the clinical presentation.
Typhus is a vasculitic process that is capable of causing various abnormal laboratory values. Any organ may be affected, and multiorgan system dysfunction or failure may occur if the illness is not diagnosed and treated in the early stages. These abnormalities, listed by organ system, may include the following:
Renal - Azotemia/proteinuria
- Leukopenia (common in the early stages of disease)
- WBC count normal/mildly elevated later
Hepatic - Mild transaminase elevations
Metabolic - Hypoalbuminemia/electrolyte abnormalities (particularly hyponatremia)
Indirect immunofluorescence assay (IFA) or enzyme immunoassay (EIA) testing can be used to evaluate for a rise in the immunoglobulin M (IgM) antibody titer, which indicates an acute primary disease.
Brill-Zinsser disease can be confirmed in a patient with a history of primary epidemic typhus who has recurrent symptoms and signs of typhus and a rise in the immunoglobulin G (IgG) antibody titer, which indicates a secondary immune response.
IFA and EIA tests can be used to confirm a diagnosis of typhus, but they do not identify the various rickettsial species.
Polymerase chain reaction (PCR) amplification of rickettsial DNA of serum or skin biopsy specimens can be used for diagnosing typhus.
The complement fixation (CF) test is a serological test that can be used to demonstrate which specific rickettsial organism is causing disease by detection of specific antibodies.
Rapid diagnostic assays for scrub typhus, such as latex agglutination tests, are currently under development.
No imaging studies are specifically indicated to aid in diagnosing typhus. Imaging studies are indicated only on a case-by-case basis to evaluate potential complications or as needed.
Chest radiography may be a complementary tool to evaluate the clinical course of scrub typhus. Chest radiographic examinations should be obtained during the first week after the onset of illness.
Rickettsia may be observed in tissue sections using Giemsa or Gimenez staining techniques.
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