**2.2.1.5 Immunodiagnosis of CE**

Immunodiagnosis procedures for serum antibody detection are used for the aetiological confirmation of imaging structures suggestive for CE. Certain proportion of patients with echinococcosis is unable to be diagnosed with highly sensitive diagnostic tests such as IgG-ELISA and false-negative results are obtained. Cysts in the brain or eye and calcified cysts often induce low or no antibody titres. Antibody response may also be low in certain human population groups and in young children. False positive results may also occur, especially in patients with other helminthic diseases. Approaches to the diagnosis of CE using immune methods are specified in table 2.


Table 2. Approaches for immunodiagnosis of CE

IgG-ELISA is the preferable test used as a primary test for detecting anti-*Echinococcus* serum antibodies. Most of the routine laboratory test systems or commercialized test kits are based on crude or semi-purified preparations of *E. granulosus* antigens. The use of the two major hydatid cyst fluid antigens, antigen 5 (thermolabile) and antigen B (thermostable), is predominantly restricted to scientific applications, and these antigens are not generally

Echinococcosis/Hydatidosis 309

immediately with complications. Aspirates of liver cysts must be analysed immediately for traces of bilirubin and protoscoleces or hooks. PAIR should only be performed under chemotherapeutic coverage, except in early pregnant patients (Filice & Brunetti, 1997).

There are some critical points to take into account when proceeding with the PAIR protocol: Prophylaxis pre- and post-procedure: albendazole is administered 24 to 4 hours before intervention and 15 days to 30 days after intervention according to the cystic size. No

Communication with biliary tree: the minimum requirements are to search for bile in

Scolicidal agent to be used: hypertonic saline (at least 15% final concentration in cyst) or

Needle vs. catheter: needle for cysts <5 cm. or in multiloculated cysts. Catheter for cysts

Follow-up: every week for the 1st month, then every month for the 1st year, the every

 Also for pregnant women, children >3 years old, patients who fail to respond to chemotherapy alone, patients in whom surgery is contraindicated, patient who refuse

Cysts with daughter cysts (CE2), and/or with detachment of membranes (CE3)

Non-cooperative patients and inaccessible or risky location of the cyst in the liver

Quantity of scolicide injected: at least 1/3 of the aspirated quantity.

Evaluation of viability: microscopic examination.

Indications for PAIR: we use this technique for patients with: Non-echoic lesion ≥ 5 cm in diameter (CE1m and l)

surgery, and patients who relapse after surgery.

The PAIR sequence is (WHO, 2001):

treatment for pregnant women.

Multiple cysts if accessible to puncture

the fluid with fast test.

95% alcohol.

>5 cm. (PAIRD)

year for 10 years.

Contraindications for PAIR:

 Cyst in spine, brain and/or heart Inactive or calcified lesion

Infected cysts

available. Secondary tests for antibody detection are used to increase specificity and these are: arc 5, identification of IgG subclasses, and immunoblotting which demonstrates the reactivity of serum antibodies with subunits of *E. granulosus* antigens (Craig, 1997; Di Felice, 1986; Ioppolo, 1996; Leggatt & McManus, 1994; Leggatt, 1992; Ligthowlers & Gottstein, 1995; Profumo, 1994; Sheperd & McManus, 1987; Siracusano & Vuitton, 1997; Wen & Craig, 1994). Generally, these tests are less sensitive, but more specific than primary test systems. Putative hydatid cyst fluid samples obtained by puncture or after surgical intervention can be tested for the presence or absence of *Echinococcus* antigen through binding of enzyme-labelled anti-*Echinococcus* (hydatid cyst fluid) antibodies in an ELISA with a monoclonal antibody against antigen 5 (Ag5) that may be useful in confirmation of the *Echinococcus* nature of the fluid (Paul & Stefaniak, 1997).
