In an Immunodiffusion Test to Diagnose Histoplasmosis, a Patientʹs Serum

Multiple Choice

In an immunodiffusion test to diagnose histoplasmosis, a patientʹs serum is placed in a well in an agar plate. In a positive test, a line forms as the serum diffuses from the well and meets material diffusing from a second well. What type of test is this?

A) a precipitation reaction
B) a direct ELISA test
C) a complement-fixation test
D) an agglutination reaction
E) an indirect ELISA test