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Rtyphiandsfiggigmspecimp

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

This blood test detects antibodies against Rickettsia typhi and spotted fever group bacteria to diagnose rickettsial infections.

Quick summary

{"Detects IgM (recent infection) and IgG (past infection) antibodies","Helps diagnose typhus and spotted fever diseases","Sample collected via blood draw from a vein","Results help guide appropriate antibiotic treatment","May require repeat testing to confirm diagnosis"}

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

Key facts at a glance

LOINC
66718-8
Short code
RT-SFG-IG
Synonyms
R typhi and SF IgG+IgM Spec-Imp
Category
cardiac
Sample
serum
Container
Serum separator tube (SST) or red top plain tube
Units
N/A
Ref low
2
Ref high
4
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Immunofluorescence assay (IFA) or Enzyme-linked immunosorbent assay (ELISA)
CPT
86757
SNOMED
122442006
Specimen volume
1-2 mL of serum
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
48–96 hours
Order
routine

What is this test?

The Rickettsia typhi and Rickettsia spotted fever group IgG and IgM test is a blood test that detects specific antibodies produced by your immune system in response to Rickettsia bacteria. These bacteria are transmitted through insect bites (typically from fleas, mites, or ticks) and can cause diseases such as murine typhus and spotted fever.

What do IgG and IgM mean?

IgM antibodies are the first antibodies your body produces when fighting a new infection. They typically appear within 1-2 weeks after infection and indicate a recent or current infection. IgG antibodies develop later and remain in your body for longer, providing immunity against future infections. Testing for both helps determine if you have an active infection or had one in the past.

How is the test performed?

A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where it is analyzed for the presence of IgG and IgM antibodies against Rickettsia typhi and spotted fever group bacteria. No special preparation is typically required before the test.

What diseases does this test detect?

This test helps diagnose two main types of rickettsial diseases: (1) Murine typhus (Rickettsia typhi), typically transmitted by fleas and causing symptoms like fever, headache, and rash; (2) Spotted fever group infections, including Rocky Mountain spotted fever and other tick-borne rickettsial diseases, which can cause severe illness if not treated promptly.

Reference range

Negative: <1:64 (IgG), <1:64 (IgM); Equivocal: 1:64 to 1:128 (IgG), 1:64 to 1:128 (IgM); Positive: >=1:128 (IgG), >=1:128 (IgM). A fourfold rise in titer between acute and convalescent sera collected 2-4 weeks apart is diagnostic.N/A

Specimen: serum

No special preparation required. Inform laboratory of recent infections, antibiotic therapy, or known immunocompromised state.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Do I need to fast 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 do positive results mean?
Positive IgM results suggest a recent or current infection. Positive IgG results may indicate a past infection or some level of immunity. Your healthcare provider will interpret these results together with your symptoms and medical history.
Do I need repeat testing?
Sometimes, a second test performed 2-4 weeks after the first may be recommended to confirm the diagnosis by showing a rise in antibody levels (seroconversion).
Is this test dangerous?
The risks are minimal and include minor bruising, bleeding, or infection at the needle site. These side effects are rare and usually temporary.
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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