Demonstration of antigenemia in patients with invasive aspergillosis by biotin-streptavidin enzyme-linked immunosorbent assay.

A biotin-streptavidin (B-SA) enzyme-linked immunosorbent assay (ELISA) was designated for the detection of Aspergillus carbohydrate antigens in serum. The sensitivity of the assay was considered to be the lowest concentration showing an absorbance above the mean of the pooled serum samples from normal adults (mean + SD = 0.118 + 0.018) plus 3 SD. This value was 1.6 ng/ml for the ELISA. The upper limit of negativity was determined by adding 0.055 to the absorbance of pooled serum samples from normal adults. The maximum absorbance value in 18 patients with invasive aspergillosis as proven by autopsy was 0.271 + 0.087 (mean + SD). Sixteen patients with invasive aspergillosis showed antigen levels ranging from 2.0 to 17.0 ng/ml. Among 14 patients from whom serum samples were sequentially obtained, 11 showed a progressive increase in concentration in accord with the progression of the infection. Only one serum sample from 42 normal subjects (0.101 + 0.025) showed false positivity for antigens. On the other hand, serum samples from 23 patients with other fungal infections (0.109 + 0.021), 48 hospitalized patients without infections (0.103 + 0.022), and 42 patients with bacterial sepsis (0.117 + 0.022) were negative for antigens. It was found that the sensitivity and specificity were 89% and 99%, respectively.