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Rprowazekigmmsmtser

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

A blood test that detects IgM antibodies against Rickettsia prowazekii, the bacteria that causes epidemic typhus.

Quick summary

{"Detects IgM antibodies indicating recent or current infection with epidemic typhus","Requires a blood sample drawn from a vein in your arm","Positive results suggest recent exposure to Rickettsia prowazekii bacteria"}

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

Key facts at a glance

LOINC
108869-9
Short code
RPROW-ABM
Synonyms
R prowazek IgM Msmt Ser
Category
cardiac
Sample
serum
Container
Serum Separator Tube (SST) or Plain Red Top Tube
Units
N/A
Ref low
1
Ref high
1.5
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Enzyme Immunoassay (EIA) / Immunofluorescence Assay (IFA)
CPT
86757
SNOMED
122441009
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. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
24–72 hours
Order
routine

What is this test?

The Rickettsia prowazekii IgM Antibody test is a blood test that looks for IgM antibodies in your blood. IgM antibodies are the first type of antibodies your immune system produces when fighting a new infection. This test specifically checks for antibodies against Rickettsia prowazekii, the bacteria that causes epidemic typhus (also known as louse-borne typhus).

Why might I need this test?

Your healthcare provider may order this test if you have symptoms of epidemic typhus, especially if you have been in areas where the disease is common or have been exposed to body lice. Symptoms of epidemic typhus include high fever (often 104°F or higher), severe headache, rash, muscle pain, and confusion. The test helps confirm whether your symptoms are caused by a recent Rickettsia prowazekii infection.

How is the test performed?

A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The blood will be collected in a tube and sent to a laboratory for analysis. The laboratory will test your blood to detect the presence and quantity of IgM antibodies specific to Rickettsia prowazekii.

What do the results mean?

A positive IgM result indicates that you have a recent or current infection with Rickettsia prowazekii. A negative result means no IgM antibodies were detected, which could mean you do not have the infection, or the infection is too early for antibodies to be detected. Your healthcare provider will interpret your results along with your symptoms and other test findings.

Reference range

Negative: <1:64 titer or <1.0 Index; Equivocal: 1:64 titer or 1.0-1.5 Index; Positive: >1:64 titer or >1.5 IndexN/A

Specimen: serum

No special preparation required. Patient does not need to fast before sample collection. Inform laboratory of any recent infections, travel history, or exposure to louse-infested environments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Is fasting required before this test?
No, you do not need to fast before this 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 to a week, depending on the laboratory. Your healthcare provider will contact you with the results.
What is epidemic typhus?
Epidemic typhus, also known as louse-borne typhus, is a serious bacterial infection caused by Rickettsia prowazekii. It is transmitted through the feces of infected body lice when they bite you. The lice feces are rubbed into the bite wound or into your eyes or mouth. Symptoms include high fever, severe headache, rash, and can be life-threatening without treatment.
How is epidemic typhus treated?
Epidemic typhus is treated with antibiotics, most commonly doxycycline. Treatment is most effective when started early. Most people improve within 48 hours of starting antibiotics.
Can I get epidemic typhus more than once?
Yes, it is possible to get epidemic typhus more than once, though repeat infections are typically milder than the first episode. A delayed recurrence (called Brill-Zinsser disease) can occur years after the initial infection.
  1. 1
    Centers for Disease Control and Prevention - Typhus FeversSource
  2. 2
    May Clinic - TyphusSource

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