RICKETTSIA RICKETTSII IGM ANTIBODY BY ELISA
- RICKETTSIA RICKETTSII IGM ANTIBODY BY ELISA
- Start Date
- Expiration Date
- CPT Codes
- Reference Test
- Transport Info
Centrifuge and immediately transfer serum to separate plastic tube
- Fasting Required?
- Patient Instructions
- Reference Range
Less than 1:64: Negative - No significant level of Rickettsia rickettsii IgM Antibody detected.
1:64 or greater: Positive - Presence of Rickettsia rickettsii IgM Antibody detected, which may indicate a current or recent infection; however, low levels of IgM antibodies may occasionally persist for more than 12 months post-infection.
Indirect Fluorescent Antibody (IFA)
This test is for antibodies to Rickettsia rickettsii. Any antibody reactivity to Rickettsia rickettsii should, however, also be considered group reactive for the Spotted Fever group (Rickettsia conorii, Rickettsia australis and Rickettsia sibirica).
Rickettsiae are gram-negative obligate intracellular organisms. A characteristic feature of the rickettsiae is that they multiply in an arthropod as part of their life cycle. With spotted fever, the invertebrate hosts are both reservoirs and vectors. These tests are for antibodies to Rickettsia rickettsii. Any antibody reactivity to Rickettsia rickettsii should, however, also be considered group reactive for the Spotted Fever group (Rickettsia conorii, Rickettsia honei, Rickettsia akari, Rickettsia japonica, Rickettsia australis, and Rickettsia sibirica). The incubation period usually ranges from three to 14 days, after which most patients develop nonspecific symptoms and signs. Onset of disease is sudden in about half of the cases. Fever and headache are the most commonly reported symptoms, but chills, myalgias, arthralgias, and anorexia are also noted. Mild pulmonary involvement, manifested by cough and infiltrates, is found in about one-third of patients with Rocky Mountain spotted fever. Rash is a hallmark of infection, but it usually follows systemic symptoms and its absence should not rule out a possible rickettsial etiology. Serious central nervous system impairment can also be seen in 25 percent of patients. Appearance of an IgM antibody response normally occurs seven to 14 days after the onset of disease. Testing immediately post-exposure is of no value without a later convalescent specimen. While the presence of IgM antibodies suggests infection, low levels of IgM antibodies may occasionally persist for more than 12 months post infection. Such a residual IgM response may be distinguished from early IgM response to infection by testing sera from patients two to three weeks later for changing levels of specific IgM antibodies. A low positive suggests past exposure or infection, while high positive results may indicate recent or past infection but are inconclusive for diagnosis. Seroconversion between acute and convalescent sera is considered strong evidence of recent infection. The best evidence for infection is a significant change on two appropriately timed specimens where both tests are done in the same laboratory at the same time.