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Test Code BILHA Schistosoma species Antibody, IgG, Serum

Useful For

Detection of antibodies to Schistosoma species

Method Name

Enzyme Immunoassay (EIA)

Reporting Name

Schistosoma Ab, IgG, S

Specimen Type

Serum


Specimen Required


Container/Tube: 

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL


Specimen Minimum Volume

0.50 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

Schistosoma species (class Trematoda) are flukes, characterized by their flat, leaf-like morphology as adults, and use of gastropod molluscs (eg, snails) as an intermediate host. The schistosomes are also referred to as the "blood flukes," of which there are 5 species known to infect humans: S mansoni, S japonicum, S haematobium, S mekongi, and S intercalatum. Among these S mansoni, S japonicum and S haematobium are most common.

 

These species have a defined geographic distribution, with S mansoni occurring throughout sub-Saharan Africa, the Middle East, and islands in the Caribbean; S haematobium found in much of the African continent and the Middle East; and S japonicum localized to China, Indonesia, and the Philippines.

 

Humans are definitive hosts for all of the Schistosoma species except for S japonicum, and infection begins with skin penetration of cercariae in contaminated water sources. The cercariae shed their bifurcated tails, becoming schistosomulae and migrate through the vascular system to the lungs, heart, and to the portal venous system in the liver. There they mature to adults, pair off and migrate to the mesenteric venules of the bowel and rectum (S mansoni, S japonicum) or venus plexus of the bladder (S haematobium). Females will shed eggs, which are moved progressively towards the lumen of the intestine (S mansoni, S japonicum) and bladder (S haematobium) and are eliminated in the feces or urine, respectively. These eggs will hatch under ideal conditions, releasing miracidia, which penetrate specific snail (mollusc) intermediate hosts and develop into cercariae, continuing the life cycle.

 

While many infections are asymptomatic, acute schistosomiasis (Katayama fever) due to S mansoni or S japonicum, may occur weeks after initial infection. Symptoms include fever, cough, abdominal pain, diarrhea, hepatosplenomegaly, and eosinophilia. Central nervous system infection is uncommon; however, cerebral granulomatous disease may be caused by migration of Schistosoma eggs into the brain or spinal cord. Cystitis and ureteritis with haematuria are associated with S haematobium infection, and can progress to bladder cancer.

 

Diagnosis of schistosomiasis can be made by detection of eggs in stool or urine samples as appropriate for each species. Antibody detection can be useful to in patients who reside in nonendemic areas, but have recently traveled to regions where Schistosoma species are found, and in whom eggs cannot be identified in fecal or urine examinations.

Reference Values

Negative

Interpretation

Negative: the absence of antibodies to Schistosoma suggests that the patient has not been exposed this trematode. A single negative result should not be used to rule-out infection with Schistosoma species.

 

Equivocal: consider repeat testing on a new serum sample in 1 to 2 weeks.

 

Positive: results suggest infection with Schistosoma. False-positive results may occur in settings of infection with other helminths, including with Echinococcus or Taenia species (see Supportive Data). Results should be considered alongside other clinical findings and exposure history.

Cautions

This assay is designed to specifically detect IgG-class antibodies to S mansoni, which are likely cross-reactive to other Schistosoma species.

 

Sensitivity for detection of antibodies to each of the Schistosoma species has not been evaluated for this assay.

 

Patients may remain seropositive by this assay following appropriate treatment and clearance of the infection.

 

Positive results should be confirmed with other laboratory findings (eg, ova and parasite examination), clinical symptoms, and suitable exposure history.

Supportive Data

The Mayo Infectious Disease Serology laboratory evaluated the accuracy of the NovaTec Schistosoma mansoni IgG ELISA (as performed in our laboratory) using 64 serum samples that were previously tested by a fluorescent microsphere immunoassay at Focus Diagnostics. A comparison of the results is shown in Table 1 below.

Table 1. Accuracy of the NovaTec Schistosoma IgG Assay compared to the Focus Diagnostics Assay

n = 64

Focus Diagnostics FMI

Positive

Negative

NovaTec

ELISA

Positive

31

1

Negative

1

20

Equivocal

5

6

Positive agreement (95% CI): 83.8% (68.5-92.6%)

Negative agreement (95% CI): 96.3% (80.2-100%)

Overall agreement (95% CI): 89.1% (82.6-97%)

 

The Mayo Infectious Disease Serology laboratory also evaluated the analytic specificity of the NovaTec S mansoni IgG ELISA using 36 serum samples positive for antibodies to other helminth and protozoa. The results are shown in Table 2 below.

Table 2. Analytical Specificity Studies.

Specimen

No. of specimens tested

No. of sera positive or equivocal by the S. mansoni IgG ELISA

Entamoeba histolytica IgG Ab

6

0

Echinococcus species IgG Ab

6

3

Strongyloides ratti IgG Ab

6

2

Taenia solium IgG Ab

6

2

Trichinella spiralis IgG Ab

6

3

Trypanosoma cruzi IgG Ab

6

1

 

The reference range for the NovaTec S mansoni IgG ELISA was established by testing serum from 50 normal donors; 47/50 (94%) of healthy individuals were negative by this ELISA.

Clinical Reference

1. Jones MK: Recent advances in diagnosis of human schistosomiasis. Asia Pacific J Trop Med. 2008;2:63-68

2. Gary DJ, Ross AG, Li YS, McManus DP: Diagnosis and management of schistosomiasis. Br Med J. 2011;342:d2651

Method Description

The qualitative immunoenzymatic determination of IgG-class antibodies against Schistosoma mansoni is based on the Enzyme-Linked Immunosorbent Assay (ELISA) technique.

 

Microtiter strip wells are precoated with Schistosoma mansoni antigens to bind corresponding antibodies of the specimen. After washing the wells to remove all unbound sample material, horseradish peroxidase (HRP)-labelled Protein A conjugate is added. This conjugate binds to antigen-antibody complexes. The immune complex formed by the bound conjugate is visualized by adding tetramethylbenzidine (TMB) substrate, which gives a blue reaction product.

 

The intensity of this product is proportional to the amount of Schistosoma-specific IgG antibodies in the specimen. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorbance at 450 nm is read using an ELISA microwell plate reader.(Package insert: NovaLisa Schistosoma mansoni, NovaTec Immundiagnostica GmbH, Dietzenbach, 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
BILHA Schistosoma Ab, IgG, S 33317-9

 

Result ID Test Result Name Result LOINC Value
BILHA Schistosoma Ab, IgG, S 33317-9