COVID-19 Antibody Test (IgM and IgG Serology)
This blood test detects antibodies against Rickettsia bacteria, including typhus and spotted fever groups, to diagnose recent or past rickettsial infections.
{"Measures IgM (early) and IgG (later) antibodies in two blood samples","Used to confirm infection when symptoms suggest rickettsial disease","First sample taken during acute illness, second sample 2-4 weeks later","Results show whether you have a current, recent, or past infection","Treatment with antibiotics is typically started based on clinical suspicion"}
Key facts at a glance
- LOINC
- 70130-0
- Short code
- RICKTT
- Synonyms
- Rickettsia TG+SFG IgG+IgM pnl Ser IF
- Category
- cardiac
- Sample
- serum
- Container
- Serum separator tube (SST) or red top tube
- Units
- N/A
- Ref low
- 64
- Ref high
- 64
- Critical range
- — – 1024 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Indirect Immunofluorescence Assay (IFA)
- CPT
- 86030
- SNOMED
- 4093005
- Specimen volume
- 1-2 mL 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
- 100
- Icterus max
- 20
- TAT
- 48–96 hours
- Order
- routine
What is this test? The COVID-19 antibody test, also called a serology test, is a blood test that looks for antibodies, which are proteins your immune system made after an infection or a vaccination.
The Rickettsia Antibody Panel is a blood test that looks for antibodies your immune system makes in response to Rickettsia bacteria. These bacteria are transmitted through bites from infected arthropods like ticks, mites, fleas, and lice. The test specifically looks for antibodies against two main groups: the Typhus Group (including epidemic typhus and murine typhus) and the Spotted Fever Group (including Rocky Mountain spotted fever).
How does the test work? A small blood sample is analyzed in a laboratory for antibodies against the virus that causes COVID-19, showing whether your immune system has responded to a past infection or vaccine.
The test uses a technique called immunofluorescence to detect antibodies in your blood. Healthcare providers typically collect two blood samples: the first during the acute phase of your illness (when you first get sick) and a second sample 2-4 weeks later during convalescence. Comparing these samples helps determine if antibody levels are rising, which confirms a recent infection.
What do IgM and IgG mean? IgM antibodies usually appear first, often within one to two weeks after infection, while IgG antibodies develop later and may stay in your blood for months as longer-lasting evidence of exposure.
IgM antibodies are the first antibodies your body produces when fighting a new infection. They typically appear within the first week or two of symptoms. IgG antibodies develop later, usually after 2-3 weeks, and provide long-term immunity. Detecting IgM suggests a recent or current infection, while IgG can indicate either a past infection or one that occurred weeks to months ago.
What happens during the test? A healthcare professional cleans your skin, wraps a band around your upper arm, and draws a small amount of blood from a vein in your arm, which usually takes less than five minutes.
A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief stinging sensation. The blood sample is sent to a laboratory where it is analyzed using immunofluorescence techniques. You will typically need to provide a second blood sample 2-4 weeks after the first to complete the testing.
Are there any risks? The risks are very low. You may feel a brief sting when the needle goes in, and some people notice mild bruising or soreness at the puncture site that fades within a day or two.
The risks are minimal and similar to any standard blood draw. You may experience slight bruising or soreness at the puncture site. In rare cases, infection or excessive bleeding may occur. The benefits of obtaining an accurate diagnosis far outweigh these minimal risks.
Reference range
Negative: IgG <1:64, IgM <1:64. Positive: IgG >=1:64, IgM >=1:64. Diagnostic significance requires 4-fold rise in titer between acute and convalescent samples collected 2-4 weeks apart.N/A
No fasting required. Collect acute phase serum at onset of symptoms. Collect convalescent serum 2-4 weeks after acute sample for serial serology. Clearly label specimens as acute or convalescent. Inform laboratory of suspected exposure history and symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Rickettsial infections can cause serious illness affecting multiple organ systems, including the heart, blood vessels, lungs, and nervous system. Early diagnosis is crucial because treatment with appropriate antibiotics (typically doxycycline) is most effective when started early. This test helps confirm the diagnosis, guide treatment decisions, and differentiate rickettsial diseases from other conditions with similar symptoms such as influenza, meningitis, or other infections. The test can also help identify outbreaks and track the spread of these diseases in communities.
Frequently asked questions
Why do I need two blood samples?
How long does it take to get results?
What do the results mean?
What symptoms suggest rickettsial infection?
Should I wait for test results before starting treatment?
Where are rickettsial diseases found?
Sources
- 1
- 2
- 3
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.
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 10, 2026. · Read our editorial policy