Depending on the resources and capabilities of clinical and reference laboratories, exoantigen extraction (immunodiffusion methods) and nucleic acid amplification test (NAAT) methods are most rapid in establishing a culture confirmation of B. dermatitidis, C. immitis and H. capsulatum. Exoantigen tests are becoming less common as NAAT methods increase in use. NAAT tests are specific, sensitive, and rapid. The one disadvantage is the cost per test.
Direct microscopic examination may not be rapid, as many strains do not produce the characteristic microscopic features until after many days of incubation.
Some yeast conversions may take as long as one week, particularly the yeast conversion of Histoplasma capsulatum.