What are the diagnostic criteria for Brucellosis (Brucella infection)?

From the Guidelines

Diagnosing brucellosis requires a combination of clinical evaluation and laboratory testing, with a thorough medical history and recognition of symptoms such as fever, sweats, fatigue, headache, and joint pain, followed by serological tests, including the Rose Bengal test and the serum agglutination test (SAT), as the most commonly used diagnostic methods 1. The diagnosis of brucellosis begins with a thorough medical history, including potential exposure to infected animals or consumption of unpasteurized dairy products.

• Recognition of symptoms such as fever, sweats, fatigue, headache, and joint pain is crucial in the diagnosis of brucellosis.
• Serological tests, including the Rose Bengal test for screening and the serum agglutination test (SAT) for confirmation, with titers ≥1:160 considered significant, are the most commonly used diagnostic methods 1.
• Blood cultures are the gold standard diagnostic test, though they may take up to 4 weeks to grow the bacteria and have variable sensitivity (15-70%) 1.
• ELISA tests offer higher sensitivity and specificity, and PCR testing provides rapid results and can detect Brucella DNA in various specimens.
• Imaging studies like MRI or CT scans may be necessary to identify complications such as neurobrucellosis or osteoarticular involvement. A definitive diagnosis typically requires either isolation of Brucella from blood, bone marrow, or other tissues, or a combination of compatible clinical presentation with positive serological testing 1.
• Early diagnosis is crucial as brucellosis can become chronic if not properly treated.
• The 2015 IDSA clinical practice guidelines recommend obtaining bacterial blood cultures and serologic tests for Brucella species in patients with subacute cases of native vertebral osteomyelitis residing in endemic areas for brucellosis 1.

From the Research

Diagnosis of Brucellosis

To diagnose brucellosis, several methods can be employed, including:

• Culture: considered the "gold standard" in the laboratory diagnosis of brucellosis due to its clinical and epidemiological relevance 2, 3
• Serological tests: indirect diagnosis by detecting antibodies against Brucella spp., despite limitations such as lack of common interpretative criteria and suboptimal specificity 4, 2, 3
• Molecular PCR-based methods: direct rapid diagnosis with high sensitivity and specificity, but requiring attention to interpretation of results 2, 3

Laboratory Techniques

Various laboratory techniques are used for the diagnosis of brucellosis, including:

• Blood culturing: although time-consuming and not always reliable, can be used for direct detection of Brucella spp. 4
• Serum agglutination test: a conventional serological test, but lacks sensitivity and specificity 4
• Enzyme-linked immunosorbent assays (ELISA): can be used for screening and confirmation of brucellosis in one step 4
• Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP): molecular techniques used to differentiate species and strains within the genus Brucella 4

Interpretation of Results

Interpretation of results from diagnostic tests for brucellosis requires attention, as:

• Positive molecular test results may not necessarily indicate an active infection, but rather a low bacterial inoculum, DNA from dead bacteria, or a patient that has recovered 2, 3
• Serological test results may be difficult to interpret in individuals repeatedly exposed to Brucella organisms 2