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Test Code ECHNO Echinococcus Antibody, IgG, Serum

Useful For

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

Method Name

Enzyme Immunoassay (EIA)

Reporting Name

Echinococcus Ab, IgG, S

Specimen Type

Serum


Specimen Required


Container/Tube: 

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.50 mL


Specimen Minimum Volume

0.20 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 30 days
  Frozen  30 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross reject

Icterus

NA

Other

NA

Clinical Information

Echinococcosis, also referred to as hydatidosis or hydatid disease, is one 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 in rural, grazing areas where dogs may feed on deceased,infected sheep or cattle. 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, which penetrates the intestinal wall and migrates through the circulatory system to various organs where it will develop into a cyst that gradually enlarges producing protoscolicies and daughter cysts that 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 manifests similar 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

Negative

Interpretation

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 and exposure history.

Cautions

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 E vogeli and E 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 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/WBa

Positive

Negative

RIDASCREEN

IgG ELISAc

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 ELISA.

Method Description

Purified antigens are bonded to a microwell plate. Antibodies that are present in the patient samples attach themselves to the antigens and are determined during the second phase of the test by using enzyme-labelled antihuman antibodies (the conjugate). The enzyme converts the colorless substrate (urea peroxide/TMP) to a blue endproduct. The enzyme reaction is stopped by adding sulphuric acid. The colour of the mixture then switches from blue to yellow. A final measurement is carried out in a photometer at 450 nm using a reference wavelength of ≥620 nm.(Package insert: RIDASCREEN Echinococcus IgG, R-Biopharm AG, Darmstadt, Germany)

Day(s) and Time(s) Performed

Tuesday, Thursday; 9 a. m.

Analytic Time

Same day/1 day

Specimen Retention Time

14 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

86682

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ECHNO Echinococcus Ab, IgG, S 32171-1

 

Result ID Test Result Name Result LOINC Value
64985 Echinococcus Ab, IgG, S In Process