Next Page

Laboratory Diagnosis

The eggs of Paragonimus westermani may be identified in sputum by direct smear, or within stools, but concentration methods may be necessary; specific egg detection rates have been reported to be low (28 to 38%). There is a standard intradermal sensitivity test which is useful in screening and diagnosis. The test is very sensitive (80 to 90%) and starts to react positively from 2 weeks after infection. This test, however, is less specific for active disease. A positive reaction persists for at least 5 years after cure and frequently up to 10-20 years. Furthermore, cross-reaction may occur in patients with clonorchiasis (Shim et al, 1991).

To overcome the low sensitivity of egg detection and low specificity of the intradermal test, serological tests that measure the serum levels of anti-Paragonimus antibody have been developed. The complement fixation (CF) test is the classic method for this purpose; it is reliable for diagnosis and for assessing the results of treatment. The test becomes positive about 4 weeks after infection and reverts to normal after successful treatment, within 6 to 12 months. However, the CF test is very laborious and requires technical competence. Again, cross reaction may occur with Clonorchis and Schistosoma.

The enzyme-linked immunosorbent assay (ELISA) is highly sensitive (92%) and is the specific anti-Paragonimus antibody test most widely used for the diagnosis of paragonimiasis in endemic areas. This technique is simple and quick. The antibody levels by ELISA drop to normal range in 4 to 24 months after successful treatment (Cho et al, 1981). Thus, tests for egg detection and anti-Paragonimus antibody are the mainstays for the diagnosis of paragonimiasis.

Back to the Table of Contents

Copyright: Palmer and Reeder

Tropical Medicine Mission Index of Diseases About Tropical Medicine Tropical Medicine Home Page Tropical Medicine Staff