What is RMSF IGG (Rocky Mountain Spotted Fever)? Lab results explained

This test measures IgG antibodies to Rocky Mountain Spotted Fever.  Rocky Mountain Spotted Fever (RMSF) is a bacterial disease which is spread through tick bites.

There are several common tick species which can carry this disease. RMSF was first seen in the Rocky Mountains area but is also prevalent in the southeastern US as well as parts of Canada, Mexico, Central America, and South America.

Most people infected with RMSF will have symptoms which include:

– fever,

– headache,

– nausea,

– vomiting,

– stomach pain,

– muscle pain,

– and lack of appetite.

The signature symptom of RMSF is a rash which develops in most people who are infected, often around the wrists and ankles. The rash typically takes the forms of small red dots or red splotches and can spread up or down the body. Because most of the symptoms of RMSF are common to other conditions and the rash may not develop early in the illness, a diagnosis based just on symptoms can be difficult.

Blood testing for RMSF antibodies is recommended. Early diagnosis and treatment are key to a successful recovery. If left untreated, Rocky Mountain Spotted Fever can lead to nerve damage, paralysis, hearing loss, mental disability, and death.

Testing for RMSF is recommended for anyone who develops symptoms after being bitten by a tick or spending time outdoors in areas where ticks are prevalent.

– RMSF Antibody testing can sometimes show false positives due to cross-reactivity with other illnesses including Lyme Disease.

– In some cases, repeat testing 1-2 weeks apart may be necessary to see if there is a significant rise in antibody levels.

– IgG antibodies may remain present even after an infection has been treated.

An RMSF IgM Antibody test is also available which may be able to detect a recent exposure. A test which includes both IgM and IgG antibodies is usually recommended but results should always be interpreted along with symptoms and other relevant medical information.

WHAT DOES IT MEAN IF YOUR RESULT IS POSITIVE (1:64)?

Titers of 1:64 are suggestive of past or possible current infection. Approx. 9% of specimens positive by EIA screen are negative by IFA.

WHAT DOES IT MEAN IF YOUR RESULT IS POSITIVE (>1:64)?

Titers >1:64 are suggestive of recent or active infection. Approx. 9% of specimens positive by EIA screen are negative by IFA.

WHAT DOES IT MEAN IF YOUR RESULT IS NEGATIVE?

A negative result for RMSF IgG (Rocky Mountain Spotted Fever) indicates that no significant level of IgG antibodies specific to Rickettsia rickettsii, the bacterium responsible for Rocky Mountain Spotted Fever, was detected in the blood. This negative result is not surprising, as antibodies against RMSF are often not detectable until at least a week after infection. It’s important to note that a single negative IgG antibody result cannot definitively rule out RMSF, especially during the early stages of infection. In cases of suspected RMSF, clinical evaluation and additional diagnostic tests may be necessary to confirm or rule out the infection. A negative IgG result should be interpreted in conjunction with other clinical findings, including symptoms and potential tick exposure. Early diagnosis and prompt treatment are crucial for managing RMSF effectively, as the antibodies may take some time to become detectable in the bloodstream.

Disclaimer:

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

The information on healthmatters.io is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.