Fluoride, Plasma (FL)

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Marshfield Clinic Public WebSite

Test Code: FLSO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

Fl (Fluoride)

Useful For

Assessing accidental fluoride ingestion

Monitoring patients receiving sodium fluoride for bone disease or patients receiving voriconazole therapy

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume	Pediatric Minimum Volume
Plasma	Sodium-heparin Green Top Tube (GTT)		3 mL	1.2 mL	1.2 mL

Collection Processing Instructions

Centrifuge immediately and transfer plasma to a plastic vial.

Specimen Stability Information

Specimen Type	Temperature	Time
Plasma	Refrigerated (preferred)	14 days
	Ambient	14 days
	Frozen	14 days

Rejection Criteria

Glass tube

Interference

In solutions of below pH 5, hydrogen ion (H[+]) complexes with the fluoride ion, thus reducing the free fluoride ion concentration and giving a falsely low reading.

At higher pH (>9), the hydroxyl ion (OH[-]) will interfere with electrodes, giving a falsely elevated reading.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Analytical Time	Methodology/Instrumentation
Mayo Clinic Laboratories	Tuesday	1-7 days	Ion-Selective Electrode (ISE)

Reference Lab

Mayo Clinic Laboratories

Test Information

Fluoride induces bone formation by stimulating osteoblasts. Because fluorides increase bone density, they are used in dental preparations and as an antiosteoporotic agent. However, prolonged high exposure to fluoride produces changes in bone morphology consistent with osteomalacia, including prolonged mineralization lag time and increased osteoid thickness. The adverse skeletal effects of fluoride are associated with plasma fluoride greater than 4 mcmol/L. Chronic fluorosis may produce osteosclerosis, periostitis, calcification of ligaments and tendons, and crippling deformities.

Prolonged exposure to the fluoride-containing antifungal agent voriconazole can produce high plasma fluoride concentrations and bone changes (periostitis). Several other medicines also contain fluoride are used for treating skin diseases (eg, flucytosine, an antifungal) and some cancers (eg, fluorouracil, an antimetabolite).

Reference Range Information

< 4.1 mcmol/L

Interpretation

Humans exposed to fluoride-treated water typically have plasma fluoride in the range of 1 to 4 mcmol/L. Those who are not drinking fluoride-treated water have plasma fluoride <1 mcmol/L. Plasma fluoride values >4 mcmol/L indicate excessive exposure and are associated with periostitis.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
82735

Synonyms/Keywords

Fl (Fluoride)

Ordering Applications

Ordering Application	Description
Centricity	Fluoride, Plasma (FL)
Cerner	None

If the ordering application you are looking for is not listed, contact your local laboratory for assistance.

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume	Pediatric Minimum Volume
Plasma	Sodium-heparin Green Top Tube (GTT)		3 mL	1.2 mL	1.2 mL

Collection Processing