Complete Blood Count (CBC) Test: What It Is, Why It Is Done, and What Your Results Mean
This blood test detects IgM antibodies against Rickettsia typhi, the bacterium that causes murine typhus (endemic typhus).
{"Detects IgM antibodies indicating recent or current infection with Rickettsia typhi","IgM antibodies typically appear 7-10 days after infection","Positive results help confirm diagnosis of murine typhus","Sample is collected from blood (serum)","Treatment with antibiotics is effective if started early"}
Key facts at a glance
- LOINC
- 110213-6
- Short code
- RTTYPIgM
- Synonyms
- R typhi IgM Msmt Ser
- Category
- cardiac
- Sample
- serum
- Container
- Serum separator tube (SST/gold top) or plain red top tube
- Units
- N/A
- Ref low
- 4
- Ref high
- 5.9
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Enzyme-linked immunosorbent assay (ELISA) or indirect immunofluorescence assay (IFA) for detection of Rickettsia typhi-specific IgM antibodies
- CPT
- 86618
- SNOMED
- 122442004
- Specimen volume
- 1.0-2.0 mL of serum minimum
- Stability
- Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 48–168 hours
- Order
- routine
What is a complete blood count (CBC) test, and what does it measure in your blood?
The Rickettsia typhi IgM Antibody test is a blood test that looks for IgM antibodies in your serum. IgM antibodies are the first type of antibodies your immune system produces when fighting a new infection. This test helps determine if you have a recent or current infection with Rickettsia typhi, the bacterium that causes murine typhus (also known as endemic typhus or fleaborne typhus).
Why is a complete blood count (CBC) performed, and when might your doctor recommend one for you?
This test is performed when you have symptoms suggestive of murine typhus, such as high fever, severe headache, rash, and muscle pain. It is especially useful when your healthcare provider suspects you may have been exposed to Rickettsia typhi, which is typically transmitted through flea bites from infected rats or other animals. The IgM test is particularly valuable because it can detect early infection, as IgM antibodies appear before IgG antibodies.
What happens during a complete blood count (CBC), and how is the blood sample collected?
A healthcare professional will draw a small sample of blood from a vein in your arm. This blood sample will be sent to a laboratory where it will be tested for the presence of IgM antibodies against Ricktressesia typhi. The procedure is quick and generally causes minimal discomfort, similar to a routine blood draw.
Understanding your complete blood count (CBC) results, including what your red blood cell, white blood cell, hemoglobin, hematocrit, and platelet levels may indicate about your overall health.
A positive IgM result suggests you have a recent or current infection with Rickettsia typhi. However, results should be interpreted by your healthcare provider along with your symptoms, physical examination, and possibly other tests. A negative result does not completely rule out infection, especially if the test was done very early in the illness when antibodies may not yet be detectable.
Reference range
Negative: < 1:64 titer or < 4.0 ELISA units; Equivocal: 1:64 titer or 4.0-5.9 ELISA units; Positive: >= 1:128 titer or >= 6.0 ELISA unitsN/A
No special preparation required. Patient may eat and drink normally before specimen collection. Inform laboratory of any recent infections, antibiotic therapy, or known exposures to rickettsial organisms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The Rickettsia typhi IgM antibody test is clinically significant for diagnosing murine typhus, a disease caused by Rickettsia typhi bacteria transmitted through flea bites. Early diagnosis is crucial because prompt treatment with appropriate antibiotics (such as doxycycline) is highly effective and can prevent complications. If left untreated, murine typhus can lead to more severe illness affecting multiple organ systems. The IgM test is particularly useful for identifying acute infections, as IgM antibodies indicate a more recent immune response compared to IgG antibodies which develop later and may persist longer.
Frequently asked questions
How is murine typhus transmitted?
What are the symptoms of murine typhus?
Is this test painful?
Do I need to fast before this test?
How is murine typhus treated?
Sources
- 1
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- 3
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
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