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HelpTest Code FL Fluoride, Plasma
Reporting Name
Fluoride, PUseful For
Assessing accidental fluoride ingestion
Monitoring patients receiving sodium fluoride for bone disease or patients receiving voriconazole therapy
Method Name
Ion-Selective Electrode (ISE)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Plasma HeparinSpecimen 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.
Specimen 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 |
Reference Values
<4.1 mcmol/L
Day(s) Performed
Tuesday
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 |
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).
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.
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)