Rickettsia

Diagnostic Tests for Rickettsia

The diagnosis of Rickettsiosis is difficult to make clinically for patients, because the symptoms are non-specific. IGeneX offers the following tests to help physicians in the accurate detection of Rickettsia.

Rickettsia rickettsii/typhi IgG Antibody

The Rickettsia Immunofluorescent Assay (IFA) is designed to detect Rickettsia-specific antibodies in human serum. For diagnostic purposesIFA test results should be used in conjunction with other data available to the diagnosing physician.

Principal

The Rickettsia IFA assay is a two-stage sandwich assay, based upon an antigen-antibody complex formation in the following steps:

  • Binding of anti-Rickettsia-specific antibodies in human serum to fixed Rickettsia
  • Binding of fluorescent-labeled anti-humanIgG/IgM antibodies to the human anti–Rickettsia antibodies bound to Rickettsia on the slide
  • Identifying green fluorescing Rickettsia organismswith a fluorescent microscope
Rickettsia-Diagnostic-Testing

Reference Range

  • Rickettsia antibody titers IgG       <40

Clinical Significance

The Rickettsia IFA is used to detect antibodies to Rickettsia species in human serum. These species include R. ricketsii and R. typhi, known to cause Rocky Mountain Spotted Fever and Murine Typhus, respectively. Titers rise during the first two-to-four weeks of illness and decline over the next six-to-12 months. In patients with previously high titers, titers of less than 160 may indicate a resolving infection. If the IFA result is negative but the clinical symptoms are present, polymerase chain reaction (PCR) testing is suggested.

Results Interpretations >
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Rickettsia rickettsiiPCR Panel – Whole Blood

The polymerase chain reaction (PCR)-based diagnostic assay for detection of Rickettsia from blood is highly specific to R. rickettsii and R. felis/typhi DNAs. The combination of the following three steps imparts a very high specificity and sensitivity to the test:

  • Hybridization/selection
  • Amplification of Rickettsia-specific DNA
  • Detection of Rickettsia-specific amplified DNA fragments

Reference Range

  • rickettsii: Negative, R. rickettsia-specific DNA not detected
  • felis/typhi: Negative, R. felis/typhi-specific DNA not detected

Clinical Significance

The Rickettsia species PCR test is an assay that detects Rickettsia species-specific DNA in clinical samples. Rickettsia 17 kDa antigen gene fragments are hybrid-selected by probes, followed by PCR amplification of the selected DNA fragment. PCR products are tested with Rickettsia-specific probes (R. rickettsii and R. felis/typhi) by southern blot assays. The primers and probes used for the selection of Rickettsia gene fragment encoding the 17 kDa antigen DNA fragments are designed from published sequences.

Limitations

  1. This test should only be performed in conjunction with southern blot assays.
  2. Results should be interpreted in conjunction with other laboratory and clinical findings.
  3. Test results can only help the physician in confirming a clinical diagnosis.

Results Interpretations >
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Which Kit to Order

Panels Blood Urine Misc
*CP1 | Co-infection Panel 1
CP4 | Co-infection Panel 4
CP5 | Co-infection Panel 5
RP1 | Rickettsia Panel 1
(*) Not yet available for New York residents.

Collection Kits

Compatible with Samples Other than Blood or Urine

Misc. Collection Kit

The Miscellaneous Collection Kit is compatible with tick-borne disease tests that require samples other than blood or urine, such as cerebral spinal fluid (CSF), tissue, placenta or breast milk.

Compatible with All Tests that Require Blood

Blood Collection Kit

The Blood Collection Kit is compatible with most of the tick-borne disease tests and panels. The panels are usually the most comprehensive available for testing for Borreliosis/Lyme disease as well as co-infection(s) with other tick-borne illnesses.

Compatible with All Tests that Require Urine

Urine Collection Kit

The Urine Collection Kit is compatible with all tick-borne disease tests that require urine samples. These tests are particularly useful during the acute phase of a tick-borne disease infection before antibodies are present as well as for seronegative patients, patients with vague symptoms of long duration, and previously-treated patients with recurring symptoms.

Receipt of payment for the testing and a signed Requisition Form is required upon submission of patient's test specimen to IGeneX, with the exception of Medicare patients.