Test Id : BRCMG

If the Brucella antibody screen, IgM or IgG, result is either positive or equivocal, then confirmation by Brucella total antibody agglutination testing will be performed at an additional charge.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Sterile vial

Specimen Volume: 1 mL

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

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

0.4 mL

Evaluating patients with suspected brucellosis

If the Brucella antibody screen, IgM or IgG, result is either positive or equivocal, then confirmation by Brucella total antibody agglutination testing will be performed at an additional charge.

Brucellosis is a major disease in humans and domesticated animals and is a systemic bacterial infection caused by gram-negative coccobacilli of the genus Brucella. Brucellosis is a zoonotic disease, and a variety of domestic animals serve as reservoir species: Brucella infects goats (Brucella melitensis), cattle (Brucella abortus), swine (Brucella suis), and dogs (Brucella canis). Transmission to humans results from direct contact with infected animals, exposure to infectious aerosols, or ingestion of unpasteurized dairy products; human-to-human transmission does not occur. While few cases are reported in the US, the majority of cases occur in the Mediterranean region, Western Asia, and parts of Latin America and Africa.

Three species of Brucella commonly cause disease in humans: B melitensis, B suis, and B abortus. Clinical manifestations of brucellosis consist of fever, sweats, malaise, weight loss, headache, and weakness. The onset may be insidious or acute, generally beginning within 2 to 4 weeks after exposure. Any organ or system of the body may be involved, although death is uncommon. Presumptive diagnosis of brucellosis can be made by detection of high or rising titers of specific antibodies, typically to smooth lipopolysaccharide (S-LPS), a major antigenic virulence determinant. Serologic tests using S-LPS can detect antibody to the three major Brucella species due to this shared epitope. IgM antibodies appear during the first week of infection followed by a switch to IgG synthesis during the second week. A variety of serologic tests have been used for diagnosis of Brucella infection. Detection of anti-Brucella antibodies using enzyme-linked immunosorbent assay (ELISA) has been demonstrated to be a sensitive diagnostic approach. However, all specimens testing positive by ELISA should be confirmed by an agglutination method to increase assay specificity.

IgG SCREEN

Negative

Reference values apply to all ages.

IgM SCREEN

Negative

Reference values apply to all ages.

In the acute stage of the disease, there is an initial production of IgM antibodies followed closely by production of IgG antibodies. IgG-class antibodies may decline after treatment; however, high levels of circulating IgG-class antibodies may be found without any active disease.

Rising levels of specific antibody in paired sera can be regarded as serological evidence of recent infection. The presence of specific IgM in a single specimen may also indicate a recent infection, although IgM-class antibodies may persist for months following acute disease.

The Centers for Disease Control and Prevention (CDC) recommends that specimens testing positive for IgG or IgM by enzyme-linked immunosorbent assay (ELISA) be confirmed by a Brucella-specific agglutination method.(1)

The CDC/Council of State and Territorial Epidemiologists case definition for human brucellosis states that the laboratory criteria for diagnosis includes the following:

1. Isolation of Brucella species from a clinical specimen

2. Four-fold or greater rise in Brucella agglutination titer between acute- and convalescent-phase serum specimens obtained more than 2 weeks apart and studied at the same laboratory

3. Demonstration by immunofluorescence of Brucella species in a clinical specimen

Positive results by ELISA that are not confirmed by Brucella-specific agglutination may represent false-positive screening results. If clinically indicated, a new specimen should be tested after 14 to 21 days.

If results of ELISA are negative and a recent infection is suspected, a new specimen should be tested after 14 to 21 days.

This test utilizes antigen derived from Brucella abortus strain W99. However, significant cross-reactivity exists for other Brucella species (except Brucella canis); therefore, the assays should not be used to differentiate infection at the species level.

B canis, a rare cause of brucellosis, may not be detected by this method.

Detection of specific IgM or IgG-class antibody to Brucella melitensis and Brucella suis by this method has not been determined.

Enzyme-linked immunosorbent assays are intended to be used as a screen only. Positive results should be followed up using an agglutination assay for confirmation. Results must be used in conjunction with symptoms, patient history, and other clinical findings.

B abortus strain RB51 is used for vaccination of animals in the US. There are currently no serologic tests to detect an antibody response to strain RB51 in humans. Per Centers for Disease Control and Prevention guidelines, routine clinical serology tests for Brucella do not detect an antibody response to strain RB51. Note that other strains besides RB51 may be used for vaccinating animals outside of the US.(2)

According to the manufacturer's package insert, 127 patient samples testing positive with the Rose-Bengal test were also examined with the Eurroimmun anti-Brucella abortus enzyme-linked immunosorbent assay, and 160 blood donors were tested. Data from these studies were as follows for anti-B abortus:

-IgG: sensitivity, 78.0%; specificity, 98.0%

-IgM: sensitivity, 56.0%; specificity, 98.0%

1. Centers for Disease Control and Prevention (CDC): Public health consequences of a false-positive laboratory test result for Brucella--Florida, Georgia, and Michigan, 2005, MMWR Morb Mortal Wkly Rep. 2008 Jun 6:57(22);603-605

2. Gunes H, Dogan M: False-positivity in diagnosis of brucellosis associated with Rev-1 vaccine. Libyan J Med. 2013;8:20417

3. Yagupsky P, Morata P, Colmenero JD. Laboratory diagnosis of human brucellosis. Clin Microbiol Rev. 2019;33(1):e00073-19. Published 2019 Nov 13. doi:10.1128/CMR.00073-19

4. Stoddard RA. Detection of Brucella spp. antibodies. In: Leber AL, Burnham CAD, eds. Clinical Microbiology Procedures Handbook. 5th ed. ASM Press; 2023:chap 13.3

Serum is tested using an enzyme-linked immunosorbent assay (ELISA) Test Kit containing microtiter strips with wells coated with Brucella abortus antigens (strain W99). In the first reaction step, diluted patient samples are incubated in the wells. Specific IgG or IgM antibodies, if present in the serum, will bind to the antigens. To detect the bound antibodies, a second incubation is carried out using an enzyme-labeled antihuman IgG or antihuman IgM (enzyme conjugate). After addition of the substrate, tetramethylbenzidine/hydrogen peroxide, and a sulfuric acid stop solution, the resulting color reaction is measured photometrically at a wavelength of 450 nm.(Package insert: Anti-Brucella abortus ELISA Test Instructions. Euroimmun Medizinische Labordiagnostika; IgM: 01/2019, IgG: 08/2020)

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This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

86622 x 2-Brucella antibody, IgG and IgM

86622-Brucella total antibody, agglutination (if appropriate)