Parassitologia. 2004 Jun;46(1-2):141-4.

The serodiagnosis of parasitic infections.

[Article in Italian]

Bruschi F1, Castagna B.

• 1Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università degli Studi di Pisa e U.O. di Microbiologia Universitaria, Azienda Ospedaliera Universitaria Pisana, Pisa.

Recently, the term of clinical immunoparasitology has been coined to indicate the application of immunological methods to the laboratory diagnosis of parasitic infections.

In particular, serological diagnosis (indirect diagnosis) is useful especially in the cases of toxocarosis, trichinellosis, echinococcosis, cysticercosis, toxoplasmosis, amoebic abscess, some filariasis, visceral leishmaniasis, schistosomiasis.

When possible, for infections caused by protozoa or helminths, the "gold standard" is represented by direct diagnosis performed by microscopic and/or macroscopic observation of the parasite.

In any case, immunological results must be interpreted in consideration of the clinical picture of the patient and confirmed possibly by finding the parasite or its genome, even using molecular methods. Furthermore, since the presence of specific antibodies can reveal an acquired infection, but not necessarily a disease, it is particularly helpful, in addition to a qualitative evaluation, a quantitative one, by determining the serum antibody titre. After recovery, the antibody levels decrease, however, they may persist for long periods, for this reason they do not help in evaluating the treatment outcome. Interpretation of serological results may be difficult when the patients originate from areas where the suspected infection is endemic, in that case, a serum positivity could reflect an old exposition to the parasite, therefore it is not related to the present clinical status. Furthermore, serology may frequently result falsely negative in not immunocompetent subjects (organ transplanted, HIV positive individuals, premature babies, diabetics).

Clinicians can interpret correctly the serological results only if the Parasitology laboratory inform them about the significant diagnostic values, the sensitivity and the specificity of the test in use.

At present time, many diagnostic kits for immunoparasitology are commercially available, and industries are developing newer and newer ones (which are not always validated).

In relation to this aspect, it should be helpful, for each of parasitic infection, to establish reference centers, not only to control the quality of commercial kits, but also as a reference point to those laboratories which use "in house" kits.

To this regard, the recent establishment of a European Centre for Control of Infectious Diseases will help. The antigen characteristics (crude, E/S, recombinant, synthetic) for assays searching for antibodies (IHA, IFA, EIA, WB) of different classes, the controls to choose for these assays, the specimen requirements will be discussed. The recent findings on the serological diagnosis of intestinal protozoa infections, malaria, leishmaniasis, echinococcosis, cysticercosis, trichinellosis, toxocariasis, schistosomiasis, strongyloidiasis will be presented.

PMID: 15305704