Section 2 : Diseases and Disorders Diagnosed Using Immunologic Tests

Abstract:

This section talks about the diseases and disorders diagnosed using immunologic tests and also discusses the serologic tests for bacteria, viruses, fungi, and parasites. Methods for detecting infection with organisms include (i) isolation and identification of organisms in the lesion; (ii) culture of organisms from the lesion, from body fluids, or from tissue samples; (iii) detection of an immune response to the organisms after an appropriate time interval; and (iv) detection of an organism’s nucleic acid in the infected host. For decades, culture and serology have been the major techniques used to detect infection, and the section concentrates on the serologic procedures. The specific diseases discussed include those due to infection with enterobacteria, gram-negative cocci and bacilli, mycobacteria, spirochetes, streptococci, and certain toxin-secreting bacteria. Serology is a major feature of the laboratory diagnosis of viral infections; it can be used to identify a particular virus as well as various serotypes and strains of the virus. Disease causing virus such as arboviruses, adenoviruses, enteroviruses, hepatitis viruses (HBV, HCV, HDV, and HEV), herpesviruses. The fungal diseases for which serologic tests are commercially available and useful are discussed; these tests are usually agglutination tests with coated latex particles or double-diffusion (DD) tests in agarose gels. Disease causing fungus such as Aspergillus, Blastomyces dermatitidis, Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum are described in the section. Rickettsial diseases causing organisms such as Rickettsia rickettsii and Bartonella Henselae, and toxoplasmosis diseases causing organisms such as Toxoplasma gondii are also discussed.