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Rickettsia conorii IgM Antibody Blood Test

Published: August 9, 2026Updated: August 14, 2026

This blood test detects IgM antibodies against Rickettsia conorii, the bacterium that causes Mediterranean spotted fever, helping your doctor identify a recent or current infection so treatment can begin promptly.

Quick summary

{"Detects early immune response to Rickettsia conorii infection","Helps diagnose Mediterranean spotted fever, a tick-borne disease","A positive result indicates recent or current infection","Sample is collected from a vein in your arm","Early antibiotic treatment is effective for this infection"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 14, 2026Editorial policy

Key facts at a glance

LOINC
110682-2
Short code
RICKCON-IGM
Synonyms
R conorii IgM Msmt Ser
Category
cardiac
Sample
serum
Container
Serum Separator Tube (SST) or plain red top tube
Units
N/A
Ref low
0
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Indirect Immunofluorescence Assay (IFA) or Enzyme-Linked Immunosorbent Assay (ELISA)
CPT
86635
SNOMED
12244004
Specimen volume
1.0-2.0 mL of serum
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C or below): 30 days
Hemolysis max
50
Lipemia max
300
Icterus max
20
TAT
48–168 hours
Order
routine

What is this test?

This test looks for IgM antibodies in your blood. IgM antibodies are the first antibodies your immune system produces when fighting a new infection. The test specifically checks for antibodies against Rickettsia conorii, a type of bacteria transmitted by dog ticks that causes Mediterranean spotted fever (also known as boutonneuse fever).

How is the test performed?

A healthcare professional will draw a small blood sample from a vein in your arm. The blood sample is then sent to a laboratory for analysis. The test detects whether IgM antibodies against Rickettsia conorii are present in your serum.

What do the results mean?

A positive result means that IgM antibodies against Rickettsia conorii were detected in your blood, indicating that you have a recent or current infection with Mediterranean spotted fever. A negative result means no antibodies were detected, but this could also mean the infection is too early to detect or you have not been exposed to the bacteria. Your doctor will interpret the results together with your symptoms and medical history.

What is Mediterranean spotted fever?

Mediterranean spotted fever is a tick-borne disease common in Mediterranean regions, parts of Africa, and the Middle East. Symptoms typically include high fever, severe headache, muscle pain, and a characteristic dark spot (eschar) at the tick bite site, followed by a rash. Most cases respond well to antibiotic treatment, especially when diagnosed early.

Reference range

Negative: <1:64 titer; Equivocal: 1:64 titer; Positive: >=1:128 titer (laboratory-specific reference ranges apply)N/A

Specimen: serum

No special preparation required. Fasting is not necessary for this test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

The Rickettsia conorii IgM antibody test is primarily used to diagnose Mediterranean spotted fever. IgM antibodies typically appear within 7-10 days after infection, making this test useful for detecting early infection. Early diagnosis is important because timely antibiotic treatment can prevent severe complications, which while rare, can include neurological issues, pneumonia, or multi-organ failure in elderly or immunocompromised patients.

Frequently asked questions

Do I need to fast before this test?
No, fasting is not required for this blood test. You can eat and drink normally before having your blood drawn.
How long does it take to get results?
Results are typically available within a few days, depending on the laboratory. Your healthcare provider will inform you when your results are ready.
Is this test painful?
You may feel a brief pinch or mild discomfort when the blood is drawn, but the procedure is generally well-tolerated and only takes a few minutes.
What happens if my test is positive?
If your test is positive, your doctor will likely prescribe antibiotics (usually doxycycline) to treat the infection. It's important to start treatment as soon as possible. Most patients recover fully with appropriate antibiotic therapy.
Can I get Mediterranean spotted fever more than once?
It is possible to be infected with Rickettsia conorii more than once, though subsequent infections are typically milder. Previous infection may provide some immunity.
  1. 1
    Mediterranean Spotted Fever - StatPearlsSource
  2. 2
    CDC - Rickettsial DiseasesSource
  3. 3
    WHO - Rickettsial diseasesSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 14, 2026. · Read our editorial policy