Evaluating patients with suspected brucellosis
Agglutination
Brucella abortus
Brucella Serology
Febrile Agglutinins
Serum
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.
If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.
0.25 mL
Gross hemolysis | Reject |
Gross lipemia | Reject |
Gross icterus | OK |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Serum | Refrigerated (preferred) | 14 days | |
Frozen | 14 days |
Evaluating patients with suspected brucellosis
Brucella species are facultative intracellular, gram-negative staining bacilli capable of producing the disease "brucellosis" in humans. Human disease is likely acquired by contact with animals infected with the organism (Brucella abortus, Brucella suis, Brucella melitensis, and occasionally Brucella canis) either by direct contact or by ingestion of meat or milk. The signs and symptoms associated with brucellosis may include fever, night sweats, chills, weakness, malaise, headache, and anorexia. The physical examination may reveal lymphadenopathy and hepatosplenomegaly. A definitive diagnosis of brucellosis is made by recovering the organism from bone marrow, blood, fluid (including urine), or tissue specimens.
In cases of suspected brucellosis, serology may assist in the diagnosis and play a supplementary role to routine culture. Antibodies to Brucella species may not become detectable until 1 to 2 weeks following the onset of symptoms, so serum specimens collected during acute disease may be negative by serology in patients with brucellosis. If serology is performed, the Centers for Disease Control and Prevention currently recommends that specimens testing positive or equivocal for IgG or IgM by a screening enzyme immunoassay be confirmed by a Brucella-specific agglutination method.(1)
<1:80
The Centers for Disease Control and Prevention (CDC) recommends that specimens testing positive or equivocal for IgG or IgM by a screening enzyme immunoassay (EIA) be confirmed by a Brucella-specific agglutination method.(1)
Negative to a titer of 1:40 or higher can be seen in the normal, healthy population. A titer of 1:80 or greater is often considered clinically significant(2); however, a 4-fold or greater increase in titer between acute and convalescent phase sera is required to diagnose acute infection.
The CDC/Council of State and Territorial Epidemiologists case definition for human brucellosis states that the laboratory criteria for diagnosis includes
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 collected 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 a screening EIA that are not confirmed by Brucella-specific agglutination may represent false-positive screening results. If clinically indicated, a new specimen should be tested after 7 to 14 days.
The tube agglutination assay was designed using antigen derived from Brucella abortus, and may not be positive in patients infected with other Brucella species (eg, Brucella canis).
Positive results by Brucella serology are not diagnostic of acute infection, as antibodies may persist for months to years following exposure. To diagnose acute infection, detection of Brucella species in culture is the recommended approach (see BRUCB / Brucella Culture, Blood).
Brucella abortus strain RB51 is used for vaccination of animals in the United States. 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 United States.(3)
Prospective serum specimens (n =114) positive for IgG or IgM antibodies, or both, by a Food and Drug Administration-approved screening enzyme immunoassay (Euroimmun) were tested for Brucella antibodies using tube agglutination (TAT) reagents supplied by the National Veterinary Services Laboratory. The results were compared to those obtained by an outside reference laboratory that used reagents supplied by Remel. Overall percent agreement was 89.5% (102/114).
In addition to prospective sera, a panel of characterized serum specimens (n =14) were tested. Overall agreement was 100% with the expected results.
Sera known to be positive for antibodies to Borrelia burgdorferi (n =5), Chlamydia species (n =1), Coxiella burnetti (n =2), Rickettsia species (n =1), or Epstein-Barr virus (n =11) were tested by the Brucella Ames TAT and all 20 specimens were found to be negative (<1:80). In addition, a serum specimen containing rheumatoid factor (n =1) was tested and found to be negative.
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. Welch RJ, Litwin CM: A comparison of Brucella IgG and IgM ELISA assays with agglutination methodology. J Clin Lab Anal. 2010;24(3):160-162
3. Gunes H, Dogan M: False-positivity in diagnosis of brucellosis associated with Rev-1 vaccine. Libyan J Med. 2013:8:20417
Serially diluted serum is added to an antigen prepared from Brucella abortus strain 1119-3. Agglutination or flocculation is assessed after incubation at 37 degrees C for 48 hours.(Package insert: Animal and Plant Health Inspection Service National Veterinary Services Laboratories, Kirsh D: US Dept of Health, Education, and Welfare; 1973; Cooke FJ, Slack MPE: Gram-negative coccobacilli. In: Cohen J, Powderly WG, Opal SM, eds. Infectious Diseases. 4th ed. Elsevier; 2017:1611-1627)
Monday, Wednesday
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.
86622
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
BRUTA | Brucella Ab, Agglutination, S | 19053-8 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
8112 | Brucella Ab, Agglutination, S | 19053-8 |