Diagnosis of Penicillium marneffei infection by quantitation of urinary antigen by using an enzyme immunoassay

Penicillium marneffei is a major cause of opportunistic infection in patien ts with AIDS in north and northeastern Thailand. A method for the quantitat ion of P. marneffei antigen in urine was developed by using fluorescein iso thiocyanate-labelled purified rabbit hyperimmune immunoglobulin G in an enz yme-linked immunosorbent assay. This method was evaluated with 33 patients with culture-proven penicilliosis and 300 controls (52 healthy subjects, 24 8 hospitalized patients without penicilliosis) from the same area in which penicilliosis is endemic. Urinary antigen was found in all 33 (100%) patien ts with penicilliosis, with a median titer of 1.:20,480. With undiluted sam ples, 67 (27%) of 248 hospital patients and 3 (6%) of 52 healthy controls w ere reactive. At a cutoff titer of 1:40, the urine antigen detection assay had a diagnostic sensitivity of 97% and specificity of 98% (positive predic tive value, 84%; negative predictive value, 99.7%). This test offers a valu able and rapid method for the diagnosis of penicilliosis in patients with A IDS and could be a useful addition to conventional diagnostic methods in ar eas in which penicilliosis is endemic.