In brucellosis, the standard agglutination test (SAT) mainly detects which antibody class?

Introduction:
Serologic diagnosis of brucellosis often begins with agglutination tests. Understanding which antibody class is primarily detected helps interpret disease phase.

Given Data / Assumptions:

• SAT uses whole-cell antigen to measure agglutinating antibodies.
• We must identify the predominant antibody class detected.

Concept / Approach:
Because of its pentameric structure, IgM agglutinates efficiently and dominates early serologic responses detected by SAT. Differentiation from IgG is performed by 2-ME testing when needed.

Step-by-Step Solution:
Recall SAT principle: lattice formation favors IgM. Early infection shows high IgM titers; IgG rises later. Therefore, SAT mainly reflects IgM.

Verification / Alternative check:
Diagnostic algorithms pair SAT with 2-ME: loss of titer with 2-ME implies IgM, persistence implies IgG, confirming SAT's initial IgM dominance.

Why Other Options Are Wrong:

• IgG: Detected better after 2-ME modification or via other assays.
• IgA / IgE / IgD: Not primary targets in standard brucellosis SAT.

Common Pitfalls:
Confusing SAT (IgM-dominant) with 2-ME (used to demonstrate IgG persistence).

Final Answer:
The SAT primarily detects IgM antibodies.