Test Id : FIL
Filaria, Blood
Useful For
Suggests clinical disorders or settings where the test may be helpful
Detecting microfilariae in peripheral blood
Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.
| Test Id | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| FILB | Filaria Bill Only | No, (Bill Only) | No |
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
In the event that microfilaria is discovered in the Knott Concentration; a Giemsa stain for identification will be performed at an additional charge.
For more information see Mosquito-borne Disease Laboratory Testing.
Method Name
A short description of the method used to perform the test
Microscopic Examination
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Elephantiasis
Lymphatic filariasis
Wuchereria bancrofti
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
In the event that microfilaria is discovered in the Knott Concentration; a Giemsa stain for identification will be performed at an additional charge.
For more information see Mosquito-borne Disease Laboratory Testing.
Specimen Type
Describes the specimen type validated for testing
Whole Blood Na Cit
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| Q00M0022 | Specimen Source |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Container/Tube: Light-blue top (3.2% sodium citrate)
Specimen Volume: 2.7 mL
Collection Instructions: Certain microfilariae have a nocturnal or diurnal periodicity, therefore the blood collection should be timed to correspond with the release of microfilariae in the peripheral circulation. For the agents of lymphatic filariasis (Wuchereria bancrofti and the Brugia species), blood should be collected between 10 p.m. and 2 a.m., whereas for detection of Loa loa, blood should be collected between 10 a.m. and 2 p.m.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
2 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood Na Cit | Ambient (preferred) | 72 hours | |
| Refrigerated | 72 hours |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Detecting microfilariae in peripheral blood
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
In the event that microfilaria is discovered in the Knott Concentration; a Giemsa stain for identification will be performed at an additional charge.
For more information see Mosquito-borne Disease Laboratory Testing.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The filariae are parasitic nematodes (roundworms) that cause significant human morbidity in tropical regions worldwide. The macroscopic adults live in the human host and release microscopic offspring (microfilariae) into the blood or skin. The microfilariae of Wuchereria bancrofti, Brugia malayi, Brugia timori, Loa loa, Mansonella perstans, and Mansonella ozzardi are found in the blood, while the microfilariae of Onchocerca volvulus and Mansonella streptocerca are found in the skin. If microfilariae are taken up by a biting insect vector (mosquitos, blackflies, midges, and deer flies), they undergo further development in the insect and can then be transmitted to other humans.
W bancrofti and the Brugia species cause a serious condition called lymphatic filariasis. The adults live in the lymphatics and cause inflammation and scarring of the lymph vessels. Over time, the lymphatic channels are obstructed, and fluid cannot drain back to the heart resulting in massive lymphedema (elephantiasis) of the affected limb or groin. W bancrofti is found in the tropics worldwide, while Brugia species are found in parts of Asia and Southeast Asia.
Loa loa causes migratory subcutaneous angioedema referred to as "calabar swellings" as the adult worm migrates throughout the body. The adult occasionally migrates across the surface of the eye, giving it the moniker "the African eye worm." Loa loa is only found in Africa.
Finally, M perstans and M ozzardi cause a relatively mild form of filariasis. Patients are often asymptomatic. When present, symptoms include fever, angioedema, headache, myalgias, arthralgias, pruritus, and neurologic manifestations. M perstans is found in parts of Africa and South America, while M ozzardi is only found in Mexico and Central and South America.
The microfilariae of these filarial worms can be seen on conventional thick and thin blood films, which allows for their definitive identification. However, microfilariae may be in low numbers, and therefore, use of concentration methods, such as the Knott's technique, improves the detection sensitivity. Some microfilariae are released into the blood at certain times of the day; W bancrofti and Brugia species are usually released between 10 p.m. and 2 a.m. (nocturnal periodicity), while L loa is released mostly from 10 a.m. and 2 p.m. (diurnal periodicity). It is therefore important to collect blood during these time periods for optimal detection sensitivity. Mansonella species microfilariae do not exhibit any periodicity and, therefore, a random blood collection is acceptable. Since the levels of parasitemia may fluctuate, multiple smears may be needed to detect the filarial worms. Blood should be obtained and examined every 8 to 12 hours for 2 to 3 days before excluding infection.
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
If positive, organism is identified.
Interpretation
Provides information to assist in interpretation of the test results
Positive results are provided with the genus and species of the
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This exam will not detect the microfilariae of Onchocerca volvulus and Mansonella streptocerca since they are found primarily in the skin. The "skin-snip" examination is the preferred method for detecting the microfilariae of these worms.
Microfilariae may be seen in peripheral blood on routine thick and thin blood films, but concentration techniques, such as the Knott's concentration and Nucleopore membrane filtration technique, offer increased detection sensitivity.
Multiple smears may be needed to detect microfilariae in blood. Repeat specimens can be collected every 8 to 12 hours over a period of 2 to 3 days.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Centers for Disease Control and Prevention (CDC) Global Health, Division of Parasitic Diseases and Malaria. Blood Specimens - Specimen Collection. DPDx - Laboratory Identification of Parasites of Public Health Concern. CDC; Updated October 28, 2020. Accessed October 31, 2022. Available at www.cdc.gov/dpdx/diagnosticProcedures/blood/specimencoll.html
2. Mathison BA, Couturier M, Pritt BS: Diagnostic identification and differentiation of microfilariae. J Clin Microbiol. 2019 Sep 24;57(10):e00706-19
Method Description
Describes how the test is performed and provides a method-specific reference
A portion of the blood specimen is concentrated by centrifugation after adding 2% formalin. The sediment is examined as a wet preparation and, if positive, the slide is air dried, fixed in methyl alcohol, and stained with Giemsa to aid in species identification.(Orihel TC, Ash LR, Ramachandran CP: Bench Aids for the diagnosis of filarial infections. World Health Organization; 1997; Garcia LS: Diagnostic Medical Parasitology. 6th ed.ASM Press; 2016; Centers for Disease Control and Prevention (CDC), Global Health, Division of Parasitic Diseases and Malaria: Diagnosis. Parasites - Lymphatic Filariasis. CDC; Updated March 16, 2018. Accessed November 2, 2022. Available at www.cdc.gov/parasites/lymphaticfilariasis/diagnosis.html)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
87015
87210
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| FIL | Filaria, B | 10662-5 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| FIL | Filaria, B | 10662-5 |