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Test Catalog

Test ID: BILHA    
Schistosoma species Antibody, IgG, Serum

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

Detection of antibodies to Schistosoma species

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

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 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 fecal or urine samples as appropriate for each species. Antibody detection can be useful for 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 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

Interpretation Provides information to assist in interpretation of the test results

Negative: No IgG antibodies to Schistosoma species detected.

 

Equivocal: Recommend follow-up testing in 10 to 14 days if clinically indicated.

 

Positive: IgG antibody to Schistosoma species detected. Differentiation between Schistosoma species is not possible by this assay. Serologic cross-reactivity may occur in individuals with other helminth infections, including with Echinococcus or Taenia species.

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

This assay is designed to specifically detect IgG-class antibodies to Schistosoma 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 Recommendations for in-depth reading of a clinical nature

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