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Test ID: ECHNO    
Echinococcus Antibody, IgG, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Detection of antibodies to Echinococcus species, including Echinococcus multilocularis and Echinococcus granulosus

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Echinococcosis, also referred to as hydatidosis or hydatid disease, is 1 of the 17 neglected tropical diseases recognized by the World Health Organization and affects over 1 million people worldwide. Echinococcus species are tapeworms or cestodes, and 2 main species infect humans: Echinococcus granulosus and Echinococcus multilocularis.

 

With respect to geographic distribution, E granulosus can be found worldwide but, more frequently, is found in rural grazing areas where dogs may feed on infected sheep or cattle carcasses. E multilocularis is largely localized to the northern hemisphere. The definitive hosts for E granulosus are dogs or other canids, while the definitive host for E multilocularis are foxes and, to a much lesser extent, canids. Echinococcus tapeworms reside in the small intestine of definitive hosts and release eggs that are passed in the feces and ingested by an intermediate host, typically sheep or cattle in the case of E granulosus or small rodents for E multilocularis. The eggs hatch in the small bowel, releasing an oncosphere that penetrates the intestinal wall and migrates through the circulatory system to various organs where it develops into a cyst that gradually enlarges producing protoscolicies and daughter cysts, which fill the interior. The definitive host becomes infected following ingestion of these infectious cysts. Humans become accidentally infected following ingestion of Echinococcus eggs.

 

In humans, E granulosus (cystic echinococcal disease) cysts typically develop in the lungs and liver, and the infection may remain silent or latent for years (5-20 years) prior to cyst enlargement and symptom manifestation. Symptomatic manifestations include chest pain, hemoptysis, and cough for pulmonary involvement and abdominal pain and biliary duct obstruction for liver infection. E multilocularis (alveolar echinococcal disease) infections manifest more rapidly than those of E granulosus and similarly to a rapidly growing, destructive tumor, resulting in abdominal pain and biliary obstruction. Rupture of cysts can produce fever, urticaria, and anaphylactic shock.

 

Diagnosis of echinococcal infections relies on characteristic finding by ultrasound or other imaging techniques and serologic findings. Fine-needle aspirates of cystic fluid may be performed; however, they carry the risk of cyst puncture and fluid leakage, which may potentially lead to severe allergic reactions. Importantly, infected individuals do not shed eggs in stool.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

Negative:

The absence of antibodies to Echinococcus species suggests that the individual has not been exposed to this cestode. A single negative result should not be used to rule-out infection (see Cautions).

 

Equivocal:

Consider repeat testing on a new serum sample in 1 to 2 weeks.

 

Positive:

Results suggest infection with Echinococcus. False-positive results may occur in settings of infection with other helminths, or in patients with chronic immune disorders. Results should be considered alongside other clinical findings (eg, characteristic findings on imaging) and exposure history.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Depending on cyst location, individuals may not develop high enough antibody titers to be detectable by serologic assays, leading to false-negative results. Cysts localized to the lungs, central nervous system or spleen, or cysts that are senescent, calcified, or dead are associated with lower serologic reactivity.

 

False-positive results may occur in patients with other helminth infections, including with Taenia species, Schistosoma species, and Strongyloides. Careful correlation with imaging findings and exposure history is required.

 

This assay may not detect antibodies to other species of Echinococcus, including Echinococcus vogeli and Echinococcus oligarthrus, both fairly uncommon causes of hydatid disease in humans.

Supportive Data

The Mayo Infectious Disease Serology laboratory evaluated the accuracy of the RidaScreen Echinococcus IgG enzyme-linked immunosorbent assay (ELISA) (as performed in our laboratory) using 58 serum samples previously tested by the serologic assays offered at Focus Diagnostics. A comparison of the result is shown in Table 1.

 

Table 1.  Accuracy of the RIDASCREEN Echinococcus IgG assay compared to the Focus Diagnostics assays

n = 58

Focus Diagnostics ELISA/WB

Positive

Negative

RIDASCREEN

IgG ELISA

Positive

19

5

Negative

0

28

Equivocal

2

4

Positive Agreement (95% CI): 90.5% (69.9-98.6)

Negative Agreement (95% CI): 86.5% (71.6-94.6)

Overall Agreement (95% CI): 87.9% (76.8-94.3)

 

The Mayo Infectious Disease Serology laboratory also evaluated the analytic specificity of the RidaScreen Echinococcus IgG ELISA by testing 36 serum samples positive for antibodies to other helminth and protozoa. The results are shown in Table 2.

 

Table 2.  Analytical specificity studies.

Specimen

No. of specimens tested

No. of specimens positive by the Echinococcus IgG ELISA

Entamoeba histolytica IgG Ab

6

1

Schistosoma mansoni IgG Ab

6

1

Strongyloides ratti IgG Ab

6

0

Taenia solium IgG Ab

6

4

Trichinella spiralis IgG Ab

6

0

Trypanosoma cruzi IgG Ab

6

0

 

The reference range for the RidaScreen Echinococcus IgG ELISA was evaluated by testing serum from 50 normal donors; 49/50 (98%) of healthy individuals were negative by this assay.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Higuita A, Brunetti E, McCloskey C: Cystic echinococcosis. J Clin Microbiol. 2016;54(3):518-523

2. Sarkari B, Rezaei Z: Immunodiagnosis of human hydatid disease: Where do we stand? World J Methodol. 2015;5(4):185-195