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HelpTest Code ACARP Acanthamoeba species Molecular Detection, PCR, Ocular
Advisory Information
Although verification experiments did not detect Acanthamoeba species DNA in contact lenses from asymptomatic adults, it is possible that PCR may detect asymptomatic colonization/contamination and, therefore, testing should not be performed on asymptomatic individuals.
Necessary Information
Specimen source is required.
Specimen Required
The preferred specimen for Acanthamoeba PCR from an ocular source is corneal scraping or biopsy.
Submit only 1 of the following specimens:
Specimen Type: Tissue, fresh
Sources: Ocular
Container/Tube: Sterile container
Specimen Volume: 5-10 mm
Collection Instructions: Submit tissue in a sterile container with 1 mL of sterile saline, minimal essential media (MEM), or viral transport media.
Preferred Paraffin-embedded tissue block:
Supplies: Tissue Block Container (T553)
Specimen Type: Formalin-fixed, paraffin-embedded tissue block (FFPE)
Sources: Ocular
Container/Tube: Tissue block
Collection Instructions: Submit a FFPE tissue block to be cut and returned.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Acceptable Paraffin-embedded tissue block:
Specimen Type: Formalin-fixed, paraffin-embedded tissue block (FFPE)
Sources: Ocular
Container/Tube: Sterile container for each individual cut section (scroll).
Collection Instructions: Perform microtomy and prepare five separate 10-micron sections. Each section (scroll) must be placed in a separate sterile container for submission.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Type: Scrapings, swabs
Sources: Eye, ocular, cornea
Container/Tube: Sterile container
Specimen Volume: 1 mL
Collection Instructions:
1. Collect corneal scrapings using a scalpel or other sharp device to remove the outer layer of cells from the eye.
2. Swish the collection device in 1 mL of sterile saline, minimal essential media (MEM), or viral transport media.
3. Remove the collection device from the collection container before submitting to the lab.
4. Specimens containing scalpel blades will be canceled.
Additional Information: Swabs are not the preferred specimen for this test and may yield false-negative results. Specimens collected using wooden shafted swabs and calcium alginate-tipped swabs will be canceled.
Specimen Type: Contact lenses
Container/Tube: Sterile container
Specimen Volume: Entire collection
Collection Instructions:
1. Place entire contact lens in a sterile container with 1 mL sterile saline, contact lens solution, viral transport media, or minimal essential media (MEM).
2. Right and Left lenses must be submitted individually using multiple sterile containers or in the original contact lens case. Multiple orders must be created.
3. Indicate Right or Left in the specimen source.
Specimen Type: Contact lens solution
Container/Tube: Sterile container
Specimen Volume: 1 mL solution
Specimen Type: Contact lens cases without lenses
Container/Tube: Sterile container
Specimen Volume: 1 mL solution or entire case
Additional Information:
1. Depending on the type of case submitted, it may be necessary to test right and left chambers individually. Multiple orders must be created.
2. Indicate Right or Left in the specimen source.
Forms
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
Useful For
Aids in the diagnosis of amebic keratitis in conjunction with clinical findings
Method Name
Real-Time Polymerase Chain Reaction (PCR)/TaqMan DNA Probe Hybridization
Reporting Name
Acanthamoeba species Detection, PCRSpecimen Type
VariesSpecimen Minimum Volume
Tissue: 5 mm biopsy
Scrapings: 0.5 mL
Contact Lens Solution: 1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Refrigerated | 7 days |
Reject Due To
| Other | Calcium alginate-tipped swab, wood swab, or transport swab containing gel; specimens containing scalpel blades, unstained slides |
Clinical Information
Acanthamoeba are ubiquitous, free-living, microscopic amebae that cause rare, but severe, infections of the eye, skin, lungs, and central nervous system (CNS). They are found worldwide in water and soil and may enter the body through inhalation, contamination of wounds, and contact lens use. As many as 24 species comprising 18 genotypes (T1-T18) have been described, although most human infections are due to genotype T4. Given their widespread distribution in the environment, many people will be exposed to Acanthamoeba during their lifetime, but very few will become sick from this exposure.
The most common form of Acanthamoeba infection is amebic keratitis (AK). Infection occurs primarily in contact lens wearers due to contamination of lenses, cleaning solutions, or storage cases. Amebae can also enter the cornea following trauma. AK is a painful, subacute corneal infection associated with extensive scarring and blindness if untreated. Cases generally respond to treatment but relapse is common. Compared to corneal infection, involvement of the CNS is rare and seen primarily in severely immunocompromised individuals such as organ transplant recipients and patients with AIDS. CNS infection may also be caused by a related ameba, Balamuthia mandrillaris.
AK is usually clinically suspected based on symptoms and confocal ophthalmologic examination. Confirmation of infection is classically identified by microscopic examination and culture of corneal tissue and contact lenses or equipment using tap water agar plate overlain with bacteria as a food source for the amebae. Unfortunately, it must be held and examined for 7 days for maximum sensitivity. PCR provides a more rapid result with similar sensitivity to culture and is, therefore, the preferred method for confirming the clinical diagnosis of AK.
Reference Values
Negative
Day(s) and Time(s) Performed
Monday through Saturday
Analytic Time
2 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics 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
87798
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ACARP | Acanthamoeba species Detection, PCR | 41429-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| SRCAS | Specimen Source | 31208-2 |
| 38058 | Acanthamoeba species PCR | 41429-2 |