Cryptococcal
antigen detection has become a routine
biological test performed for patients with
AIDS. The poor prognosis of
cryptococcosis explains the need for reliable tests. We evaluated the performances of a newly commercialized agglutination test that uses a
monoclonal antibody specific for cryptococcal capsular
polysaccharide (Pastorex Cryptococcus; Sanofi-Diagnostics Pasteur, Marnes-la-Coquette, France) and compared them with those of tests that use polyclonal
immune sera (Cryptococcal
Antigen Latex Agglutination System, Meridian Diagnostics, Inc., Cincinnati, Ohio; and Crypto-LA, International
Biological Labs Inc., Cranbury, N.J.). The sensitivities and specificities of the tests were compared by using purified
polysaccharides and yeast
suspensions. Clinical specimens (131 serum samples, 41 cerebrospinal fluid samples, 34 urine samples, and 19 bronchoalveolar lavage samples) from 87 human immunodeficiency virus-positive subjects with (40 patients) and without (47 patients) culture-proven
cryptococcosis were retrospectively tested during a blinded study. The effect of
pronase treatment of samples was assessed for Pastorex Cryptococcus and the Cryptococcal
Antigen Latex Agglutination System, and the
antigen titers were compared. Our results show that (i) during the screening, concordance among the three tests was 97%; (ii) the use of
pronase enhanced both the sensitivities and specificities of the Pastorex Cryptococcus test; (iii) titers agreed for 67% of the cerebrospinal fluid samples and 60% of the serum samples; and (iv)
cryptococcosis was detected equally well with Pastorex Cryptococcus and with the other tests, whatever the infecting serotype (A, B, or D). The meaning of in vitro sensitivity and the relationship between titers and sensitivity are discussed. The results show that Pastorex Cryptococcus is a rapid and reliable test for the detection of cryptococcal
antigen in body fluids and suggest that kits cannot be used interchangeably to monitor
antigen titers in patients.