The value of immunological tests in mycotic disease diagnosis: a reference centre's experiences

Abstract

lmmunological tests have been widely used as indirect evidence of mycotic infection and have diagnostic value. Some of these tests can be easily adapted to be used in laboratories having a lower level of complexity. The National lnstitute of Health's Microbiology Group's Micology Laboratory is a reference centre for the diagnosis of systemic mycoses in Colombia. Thus, and having the intention of establishing a national network, four regional laboratories were selected and their personnel trained in immunological techniques so that they could carry out histoplasmosis and paracoccidioidomycosis diagnoses. The techniques employed were immunodifusion (ID), for histoplasmosis, paracoccidioidomycosis and aspergillosis, complement fixation (CF) for histoplasmosi and paracoccidioidomycosis and latex agglutination tests for antigenaemia in cryptococosis. In a period of 7 years (1990-19976), the laboratories processed 6,841 sera samples, corresponding to 6,411 patients having diagnoses compatible with systemic mycosis. The four regional laboratories analysed 1,918 (28%) samples and the reference centre 4,923 (72%). Total reactivity was 13.5% (923/6,841), broken down as follows: histoplasmosis 42.5%, paracoccidioidomycosis 33% cryptococosis 21 2% and aspergillosis 3.3%. The total number of diagnosed cases was 441: 155 histoplasmosis, 120 paracoccidioidomycosis, 138 cryptococcosis and 28 aspergillosis. The use of the ID technique in the regional centres allowed the diagnosis of 31% of patients as having histoplasmosis, 41.6% having paracoccidoidomycosis and 53.6% as having aspergillosis, which indicates that early diagnosis can be carried at regional level. The ID test sensitivity and simplicity constitute an excellent resource for those laboratories having less complexity, at regional level, which operate in endemic areas.