Patient selection: acute pulmonary histoplasmosis (not subacute or chronic)
Recommended test battery which should detect most (93%) of cases:
(1) Histoplasma antigen in blood
(2) Histoplasma antigen in urine
(3) serum antibody to Histoplasma by complement fixation (immunodiffusion is insensitive)
Observations:
(1) The antigen test is not specific for histoplasma and can be positive in other deep fungal infections.
(2) The more severe the histoplasmosis the more likely that an antigen test will be positive.
(3) The antibody test is more likely to be positive with time, so repeat testing can be helpful.
(4) A patient with severe immunosuppression or immunodeficiency may have a false negative test for antibody.
(5) Examination (microscopic, antigen, culture) of bronchoalveolar lavage fluid can detect cases not found by the initial battery.
(6) Open biopsy of a lung lesion may be necessary for diagnosis.
(7) Environmental testing at an implicated exposure site may be helpful.
(8) If other people have shared a common exposure then comparison of results may be helpful.
