Abstract
In order to identify patients with pulmonary cryptococcosis, we performed screening by the latex agglutination test for detection of serum cryptococcus antigen in patients with respiratory disease between 1981 and June 1986. We found 49 positive cases (1.9%) among 2, 623 tested patients. Of those 49 positive cases, only 3 cases were confirmed to be true positive (0.1%) and the other 46 cases were false positive, including 20 cases due to rheumatoid factor. In addition, there were 3 false negative cases, as determined by histological examination and fungal culture.
Using a new latex agglutination test involving pretreatment of patient's serum with a protease solution to remove the rheumatoid factor, we found 8 cases of pulmonary Cryptococcosis among 1, 231 patients with respiratory disease between July 1986 and 1988. All 8 cases were true positives, and there were no false positive cases. This new latex agglutination test was not interfered by rheumatoid factor. However, two cases showed a false negative result.
On the other hand, we also assayed the serum antibody titers by an agglutination test using a formalin killed yeast cell suspension in 861 patients with respiratory disease. Among 36 positive cases (4.2%), 3 cases were diagnosed as pulmonary cryptococcosis.
The latex agglutination test, especially when combined with pretreatment of serum with protease, is thus a highly useful diagnostic screening tool for detection of patients with pulmonary cryptococcosis. It is difficult to diagnose pulmonary cryptococcosis by radiological techniques because the X-ray findings are variable and usually not specific. We also stress that latent infection with Cryptococcus neoformans is not as rare a disease as had been thought.
