Sodium fluoride Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Sodium fluoride and links to relevant pages within the course.
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|False Negative Results|
False negative results occur when elements present in the urine interfere with either the enzymatic reaction or prevent the oxidation of potassium iodide. Examples of such substances include: large quantities of ketones aspirin ascorbic acid > 50 mg/dL with some reagent strips levadopa 5-hydroxyindoleacetic acid homogentisic acid sodium fluoride ( a preservative)A specific gravity higher than 1.020 may lower glucose reagent sensitivity, especially in the presence of a high urine pH. Exposing reagent strips to excess humidity may also reduce glucose reagent reactivity.Check the package insert of the reagent strips used in your laboratory for interfering substances that may affect glucose results.
|Sodium fluoride is an excellent preservative for collecting glucose specimens because:||View Page|
|Gray top tubes|
Contain an inhibitor of glycolysis, such as sodium fluoride.May also contain an anticoagulant such as potassium oxalate.
Used for accurate determination of glucose levels.
Blood may be collected into either:Red top (clot) tubes.Speckle top tubes (serum separator tube).Gray top tubes specifically designed to preserve glucose levels.
Gray top tubes contain additives such as sodium fluoride or potassium oxalate, which prevent metabolism of glucose by blood cells.
|Order of Draw|
Blood collection tubes must be filled in a specific order to avoid specimen contamination from the additive in the preceding tube. The following order of draw is an accepted laboratory standard. 1. Tubes or bottles for blood cultures 2. Light-blue top tubes (sodium citrate) 3. Serum tubes (with or without clot activator) 4. Green top tubes (sodium or lithium heparin) 5. Lavender or pink top tubes (Potassium EDTA) 6. Gray (Sodium fluoride and sodium or potassium oxalate)
|Blood Collection Tubes|
Most blood collection tubes contain an additive that either accelerates clotting of the blood (clot activator) or prevents the blood from clotting (anticoagulant). A tube that contains a clot activator will produce a serum sample when the blood is separated by centrifugation and a tube that contains an anticoagulant will produce a plasma sample after centrifugation. Some tests require the use of serum, some require plasma, and other tests require anticoagulated whole blood. The table below lists the most commonly used blood collection tubes. Tube cap color Additive Function of Additive Common laboratory tests Light-blue 3.2% Sodium citrate Prevents blood from clotting by binding calcium Coagulation Red or gold (mottled or "tiger" top used with some tubes is not shown) Serum tube with or without clot activator or gel Clot activator promotes blood clotting with glass or silica particles. Gel separates serum from cells. Chemistry, serology, immunology Green Sodium or lithium heparin with or without gel Prevents clotting by inhibiting thrombin and thromboplastin Stat and routine chemistry Lavender or pink Potassium EDTA Prevents clotting by binding calcium Hematology and blood bank Gray Sodium fluoride, and sodium or potassium oxalate Fluoride inhibits glycolysis, and oxalate prevents clotting by precipitating calcium. Glucose (especially when testing will be delayed), blood alcohol, lactic acid