Special Precautions/Comments:

N.B. Test sensitivity depends on cyst site:  Liver 96%, pulmonary 76%, skeletal 60%, other sites vary.  Brain hydatid rarely shows positive serology.

Interferences:  Serological cross-reactions, giving rise to false positives, can occur with other parasitic infections, particularly larval cestodes, and filarial worms and with some neoplasms.

False negatives may occur (about 8%) and are more common in patients with extra-hepatic cysts.  False negatives can be due to calcified cysts.

Method:  Enzyme immunoassay (EIA) screening test for the detection of Echinococcus species antigen and associated IgG antibodies. Positive samples will be confirmed by indirect haemagglutination (IHA) for the presence of IgG antibodies using Echinococcus granulosis antigen. Calibration: -.  EQA scheme: -. IQC: -.

Interpretation:  Results will be reported as Positive, Equivocal or Negative. Equivocal samples will retested by IHA, however a result is only considered clinically significant if both EIA and IHA tests are positive. If the sample shows equivocal results, suggest repeating serology in 1 months’ time.

Interpretive comments will be provided where applicable. The sensitivity of the ELISA is estimated to be 97%, the cases with negative serology but subsequently proven hydatid disease have mainly been those patients with extra-hepatic lesions. For diagnostic purposes, the results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings.

For further information contact Liverpool School of Tropical Medicine (LSTM).

Additional Information:

Background information: Human echinococcosis is a zoonotic disease caused by tapeworms of the genus Echinococcus. Where infection occurs due to a species complex centred on Echinococcus granulosus the form is referred to as cystic echinococcosis (CE), also known as hydatid disease. Human infection with E. granulosus leads to the development of one or more hydatid cysts located most often in the liver and lungs, and less frequently in the bones, kidneys, spleen, muscles and central nervous system. Abdominal pain, nausea and vomiting are commonly seen when hydatids occur in the liver. If the lung is affected, clinical signs include chronic cough, chest pain and shortness of breath. Other signs depend on the location of the hydatid cysts and the pressure exerted on the surrounding tissues. Non-specific signs include anorexia, weight loss and weakness. Although globally distributed, CE is considered endemic to Argentina, Peru, East Africa, Central Asia and China. The highest prevalence is found in rural areas where older animals are slaughtered.