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Epic Test Code LAB3871 Strongyloides Antibody, IgG, Serum

Additional Codes

MML: STRNG

Useful For

Screening for the presence of IgG-class antibodies to Strongyloides

 

This test is not useful for monitoring patient response to therapy as IgG-class antibodies to Strongyloides may remain detectable following resolution of infection.

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Reporting Name

Strongyloides Ab, IgG, S

Specimen Type

Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


Specimen Minimum Volume

0.4 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject
Heat inactivated specimen Reject

Clinical Information

Strongyloidiasis is caused by Strongyloides stercoralis, a nematode endemic to tropical and subtropical regions worldwide. S stercoralis is also prominent in the Southeastern US, including in rural areas of Kentucky, Tennessee, Virginia, and North Carolina. A small series of epidemiological studies in the US identified that 0% to 6.1% of individuals sampled had antibodies to S stercoralis.

 

S stercoralis has a complex lifecycle that begins with maturation to the infective filariform larva in warm, moist soil. The larvae subsequently penetrate exposed skin and migrate hematogenously to the lungs, from where they ascend the bronchial tree and are swallowed. Once in the small intestine, filariform larva matures into the adult worms that burrow into the mucosa. Gravid female worms produce eggs that develop into noninfectious rhabditiform larvae in the gastrointestinal tract and are eventually released in the stool. The time from dermal penetration to appearance of Strongyloides in stool samples is approximately 3 to 4 weeks.

 

The most common manifestations of infection are mild and may include epigastric pain, mild diarrhea, nausea, and vomiting. At the site of filariform penetration, skin may be inflamed and itchy-this is referred to as "ground itch." Migration of the larva through the lungs and up the trachea can produce a dry cough, wheezing, and mild hemoptysis. Eosinophilia, though common among patients with strongyloidiasis, is not a universal finding, and the absence of eosinophilia cannot be used to rule-out infection.

 

In some patients, particularly those with a depressed immune system, the rhabditiform larvae may mature into the infectious filariform larvae in the gastrointestinal tract and lead to autoinfection. The filariform larvae subsequently penetrate the gastrointestinal mucosa, migrate to the lungs, and can complete their lifecycle. Low-level autoinfection can maintain the nematode in the host for years to decades. Among patients who become severely immunocompromised, however, autoinfection may lead to hyperinfection and fatal disseminated disease. Hyperinfection has also been associated with underlying human T-cell lymphotropic virus type 1 (HTLV-1) infection. Uncontrolled, the larvae can disseminate to the lungs, heart, liver, and central nervous system. Septicemia and meningitis are common in cases of Strongyloides hyperinfection due to seeding of the bloodstream and central nervous system with bacteria originating from the gastrointestinal tract.

Reference Values

Negative

Reference values apply to all ages.

Interpretation

Positive:

IgG antibodies to Strongyloides were detected, suggesting current or past infection. False-positive results may occur with other helminth infections (eg, Trichinella, Taenia solium). Clinical correlation is required.

 

Negative:

No detectable levels of IgG antibodies to Strongyloides. Repeat testing in 10 to 14 days if clinically indicated.

Cautions

False-positive results may occur with other helminth infections, including prior exposure to Entamoeba histolytica, Ascaris, Taenia solium, Fasciola species, Echinococcus species, Schistosoma species, and Toxocara (per assay manufacturer).

 

This assay should not be used alone to establish a diagnosis of strongyloidiasis. Results should be correlated with other laboratory findings and through clinical evaluation.

 

False-negative results may occur during acute or localized infection. A single negative result should not be used to rule-out infection.

 

The seroprevalence of IgG-class antibodies to Strongyloides stercoralis ranges from 0% to 6.1% in the United States.

Supportive Data

Accuracy:

The Bordier Strongyloides enzyme immunoassay was compared to the Strongyloides luciferase immunoprecipitation (LIPS) assay as performed at the National Institutes of Health and to the SciMedix Strongyloides IgG enzyme-linked immunosorbent assay using 102 serum samples. Based on prior publications, the LIPS assay was considered the gold standard comparator for this evaluation.(1,2) The comparative data is shown below in Tables 1, 2, and 3:

 

Table 1. Comparison of results between the Bordier and NIH LIPS assays (n=102)

 

NIH LIPS

Positive

Negative

Bordier

Positive

51

12

Negative

3

36

 

 

 

 

 

Positive Agreement: 96.2% (51/53); 95% CI: 86.5%-99.7%

Negative Agreement: 75.0% (36/48); 95% CI: 61.1%-85.2%

Overall Agreement: 85.3% (87/102); 95% CI: 77.0%-91.0%

 

Table 2. Comparison of results between the Bordier and SciMedx assays (n=102)

SciMedx

Positive

Negative

Equivocal

Bordier

Positive

45

13

5

Negative

8

30

1

 

 

 

 

 

 

Positive Agreement: 84.9% (45/53); 95% CI: 72.7%-92.4%

Negative Agreement: 69.8% (30/43); 95% CI: 54.8%-81.5%

Overall Agreement: 73.5% (75/102); 95% CI: 64.2%-81.2%

 

Table 3. Comparison of results between the SciMedx and NIH LIPS assays (n=102)

NIH LIPS

Positive

Negative

SciMedix

Positive

42

11

Negative

7

36

Equivocal*

5

1

 

 

 

 

 

 

 

 

*Equivocal results were excluded from calculation of positive and negative agreement.

 

Positive Agreement: 85.7% (42/49); 95% CI: 73.0%-93.2%

Negative Agreement: 76.6% (36/47); 95% CI: 62.6%-86.6%

Overall Agreement: 76.5% (78/102); 95% CI: 67.3%-83.7%

 

Reference Range:

Evaluation was performed on 100 normal donor serum samples by the Bordier Strongyloides assay and 99% (99/100) were negative.

Day(s) Performed

Monday, Wednesday, Thursday, Friday

Report Available

Same day/1 to 4 days

Specimen Retention Time

14 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

86682

NY State Approved

Yes

Testing Algorithm

For more information see Parasitic Investigation of Stool Specimens Algorithm.

Forms

If not ordering electronically, complete, print, and send Infectious Disease Serology Test Request (T916) with the specimen.