Sign in →

EPIC CODE: LAB1209 Q Fever Antibody, IgG and IgM, Serum

Additional Codes

Sunquest:   QFABM
Mayo:          QFP
Previously:  ARUP 2012634, 2012632 

Reporting Name

Q Fever Ab, IgG and IgM, S

Useful For

Diagnosis of Coxiella burnetii, the causative agent of Q fever

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Ordering Guidance

This test should be used to monitor Q Fever antibody titers following treatment.

For initial diagnosis of Q Fever (Coxiella burnetii) infection, order QFEVR / Q Fever Antibody Screen with Titer Reflex, Serum.

Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values













Reference values apply to all ages.

Day(s) Performed

Monday through Saturday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

86638 x 4

LOINC Code Information

Test ID Test Order Name Order LOINC Value
QFP Q Fever Ab, IgG and IgM, S 77175-8


Result ID Test Result Name Result LOINC Value
80965 Q Fever Phase I Ab, IgG 34716-1
24011 Q Fever Phase II Ab, IgG 34717-9
81115 Q Fever Phase I Ab, IgM 9710-5
24009 Q Fever Phase II Ab, IgM 9711-3
24010 Interpretation 69048-7

Clinical Information

Q fever, a rickettsial infection caused by Coxiella burnetii, has been recognized as a widely distributed zoonosis with the potential for causing both sporadic and epidemic disease. The resistance of C burnetii to heat, chemical agents, and desiccation allows the agent to survive for extended periods outside the host.


C burnetii is spread by the inhalation of infected material, largely from dried sheep and goat reproductive material; the organism is also shed in feces, milk, nasal discharge, placental tissue, and amniotic fluid from ruminant animals.


The clinical spectrum of disease ranges from unapparent to fatal. Respiratory manifestations usually predominate; endocarditis and hepatitis can be complications.


During the course of the infection, the outer membrane of the organism undergoes changes in its lipopolysaccharide structure, called phase variation. Differences in the host antibody response between phase I and phase II antigens can help classify infections as either acute or chronic:

-In acute Q fever, the phase II antibody is usually higher than the phase I titer, often by 4-fold, even in early specimens. Although a rise in phase I as well as phase II titers may occur in later specimens, the phase II titer remains higher.

-In chronic Q fever, the reverse situation is generally seen. Serum specimens collected late in the illness from chronic Q fever patients demonstrate significantly higher phase I titers, sometimes much greater than 4-fold.

-In the case of chronic granulomatous hepatitis, IgG and IgM titers to phase I and phase II antigens are quite elevated, with phase II titers generally equal to or greater than phase I titers.

-Titers seen in Q fever endocarditis are similar in magnitude, although the phase I titers are quite often higher than the phase II titers.


Phase I antibody titers greater than or equal to phase II antibody titers are consistent with chronic infection or convalescent phase Q fever.


Phase II antibody titers greater than or equal to phase I antibody titers are consistent with acute/active infection.


A negative result argues against Coxiella burnetii infection. If early acute Q fever infection is suspected, collect a second specimen 2 to 3 weeks later and retest.


In Q fever sera, it is common to see IgG titers of 1:128 or greater to both phase I and phase II antibody titers. IgG class antibody titers appear very early in the disease, reaching maximum phase II titers by week 8 and persisting at elevated titers for longer than a year. Phase I titers follow the same pattern, although at much lower levels, and may not be initially detected until convalescence.


In Q fever sera, it is common to see IgM titers of 1:64 or greater.


IgM class antibody titers appear very early in the disease, reaching maximum phase II titers by week 3 and declining to very low levels by week 14. Phase I titers follow the same pattern, although at much lower levels, and may not be initially detected until convalescence.


Serologic responses are time dependent. Specimens collected too early in the disease may not have detectable antibody levels. A second specimen collected 2 to 3 weeks may be necessary to detect antibody.


Low level positive titers (ie, <1:256) may remain for prolonged periods of time following resolution of disease.

Clinical Reference

1. Hartzell JD, Marrie TJ, Raoult D: Coxiella burnetii (Q fever). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:2360-2367

2. Anderson A, Bijlmer H, Fournier PE, et al. Diagnosis and management of Q fever--United States, 2013: recommendations from CDC and the Q Fever Working Group. MMWR Recomm Rep. 2013 Mar 29;62(RR-03):1-30. Erratum in: MMWR Recomm Rep. 2013 Sep 6;62(35):730

Method Description

An indirect immunofluorescence test is used for the measurement of IgM and IgG antibodies to Coxiella burnetii. Specific antibodies present in the serum of the patient react with rickettsial cells that have been previously fixed on a glass microscope slide. Fluorescein-labeled antihuman IgG or IgM conjugate is used to stain specific antibody bound to the substrate cells. The slides are examined with a fluorescence microscope for characteristic, apple-green fluorescence of the infected cell.(Edligner B: Immunofluorescence serology: a tool for prognosis of Q fever Diagn Microbiol Infect Dis. 1985;3:343-351; package inserts: Q fever IFA IgG. Focus Diagnostics, Inc; 05/2018; Q fever IFA IgM. Focus Diagnostics, Inc; 05/2018)

Report Available

Same day/1 to 3 days

Specimen Retention Time

14 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

NY State Approved


Method Name

Indirect Immunofluorescence


If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.

Secondary ID