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HelpMayo Test ID FL Fluoride, Plasma
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Green top (sodium heparin)
Submission Container/Tube: Plastic vial
Specimen Volume: 3 mL
Collection Instructions: Centrifuge and aliquot plasma into a plastic vial. Glass tubes are not acceptable.
Useful For
Assessing accidental fluoride ingestion
Monitoring patients receiving sodium fluoride for bone disease or patients receiving voriconazole therapy
Method Name
Ion-Selective Electrode (ISE)
Reporting Name
Fluoride, PSpecimen Type
Plasma HeparinSpecimen Minimum Volume
1.2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Heparin | Refrigerated (preferred) | 14 days | |
| Ambient | 14 days | ||
| Frozen | 14 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Clinical 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 Values
<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 less than 1 mcmol/L. Plasma fluoride values greater than 4 mcmol/L indicate excessive exposure and are associated with periostitis.
Cautions
In solutions 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.
Clinical Reference
1. Cardos VES, Whitford GH, Aoyama H, et al. Daily variations in human plasma fluoride concentrations. J Fluorine Chem. 2008:129;1193-1198
2. Wermers RA, Cooper K, Razonable RR, et al. Fluoride excess and periostitis in transplant patients receiving long-term voriconazole therapy. Clin Infect Dis. 2011 1;52(5):604-611
3. Agency for Toxic Substances and Disease Registry: Toxicological profile for fluorides, hydrogen fluoride, and fluorine. US Department of Health and Human Services 2003. Accessed February 09, 2024. Available at www.atsdr.cdc.gov/ToxProfiles/tp11.pdf
4. Sodi R: Vitamins and trace elements. In: Rifai N, Chiu RWK, Young I, Burnham CD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:chap 39
Method Description
The fluoride electrode consists of a single-crystal lanthanum fluoride membrane and an internal reference bonded into an epoxy body. The crystal is an ionic conductor in which only fluoride ions are mobile. When the membrane is in contact with a fluoride solution, potential develops across the membrane. This potential depends on the level of free fluoride ions in solution and is measured against an external constant reference potential with a digital pH/mV meter.(Instruction manual: Fluoride Ion Selective Electrode User Guide. Thermo Scientific; 09/2016)
Day(s) Performed
Tuesday
Report Available
2 to 8 daysSpecimen Retention Time
14 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. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82735
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FL | Fluoride, P | 14726-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 8641 | Fluoride, P | 14726-4 |