Phosphorus Test
How is it used?
Phosphorus testing is very important in people who are malnourished or who are being treated for ketoacidosis. Phosphorus testing is used to help diagnose and evaluate the severity of conditions and diseases that affect the gastrointestinal tract, interfering with the absorption of phosphorus, calcium, and magnesium. Testing also can help to diagnose disorders that affect the kidneys, interfering with mineral excretion and conservation, and phosphorus levels are carefully monitored in people with kidney failure.
When a person has a known problem that affects their phosphorus and/or calcium levels, phosphorus levels may be monitored regularly to determine the effectiveness of treatment. Usually, it is not a stand-alone test.
While phosphorus levels are most commonly performed on blood samples, timed urinephosphorus measurements also may be used to monitor phosphorus elimination by the kidneys.
When is it ordered?
A phosphorus test is often ordered to help diagnose diseases and conditions that cause problems with the body’s utilization of calcium. The test may aid in the diagnosis of problems withhormones, such as parathyroid hormone (PTH), and Vitamin D, which functions as a hormone, that regulate the body’s calcium level and, to a lesser degree, phosphorus levels.
Although abnormal phosphorus levels usually cause no symptoms, phosphorus testing often is performed as a follow-up to an abnormal calcium level and/or related symptoms, such as fatigue, muscle weakness, cramping, or bone problems.
Phosphorus testing may be ordered when symptoms suggest kidney and gastrointestinal disorders.
If conditions causing abnormal phosphorus and/or calcium levels are found, testing for both may be ordered at regular intervals to monitor treatment effectiveness.
If you have a kidney disorder, kidney stones, or uncontrolled diabetes, your doctor may monitor phosphorus levels to make sure that you are not excreting or retaining excessive amounts.
What does the test result mean?
Dietary deficiencies in phosphorus are rare but may be seen with alcoholism and malnutrition. Low levels of phosphorus (hypophosphatemia) may also be due to or associated with:
• Hypercalcemia, especially due to hyperparathyroidism
• Overuse of diuretics
• Severe burns
• Diabetic ketoacidosis (after treatment)
• Hypothyroidism
• Hypokalemia
• Chronic antacid use
• Rickets and osteomalacia (due to Vitamin D deficiencies)
Higher than normal levels of phosphorus (hyperphosphatemia) may be due to or associated with:
• Kidney failure
• Hypoparathyroidism (underactive parathyroid gland)
• Diabetic ketoacidosis (when first seen)
• Phosphate supplementation
Is there anything else I should know?
Abnormally high levels of phosphorus can lead to organ damage due to calcification.
Phosphate levels are normally higher in children than in adults because their bones are actively growing. Low phosphate levels in children can inhibit bone growth.
Soft drinks and pre-packaged food items are high in phosphorus content, which some nutritionists believe contributes to over consumption of phosphorus.
Test results may be impacted by the use of enemas and laxatives containing sodium phosphate, excess Vitamin D supplements, and by intravenous glucose administration.
Precautions and Toxicity
Precautions: Phosphorus/phosphate salts should be used cautiously or avoided in patients with kidney impairment, liver cirrhosis, heart failure, unstable angina, recent heart surgery, hyperphosphatemia (low phosphate), hypocalcemia (low calcium), hypokalemia (low potassium), hypernatremia (high sodium), Addison's disease, ascites, intestinal obstruction or ileus, bowel perforation, severe chronic constipation, acute colitis, toxic megacolon, hypomotility syndrome (such as hypothyroidism, scleroderma), or gastric retention. Sodium phosphate enemas should be avoided in people with congenital or acquired abnormalities of the intestine. There is a particularly increased risk of hyperphosphatemia and hypocalcemia in people with kidney disease, liver disease, hypoparathyroidism, severe hyperthyroidism, Addison's disease/adrenal insufficiency, severe heart disease, lactic or respiratory acidosis, rhabdomyolysis, or tumor lysis syndrome. Hyperphosphatemia from dietary causes may occur when kidney function is only 20% of normal, and even typical levels of dietary phosphorus may lead to hyperphosphatemia. Serum electrolytes should be closely monitored when phosphates are used by people with any degree of kidney impairment.
Toxicity: Excessive intake of phosphates can cause potentially serious or life-threatening toxicity. Intravenous, oral, or rectal/enema phosphates may cause electrolyte disturbances including hypocalcemia (low calcium blood levels), hypomagnesemia (low magnesium blood levels), hyperphosphatemia (high phosphorus blood levels), or hypokalemia (low potassium levels). Calcification of non-skeletal tissues (particularly in the kidneys), severe hypotension (low blood pressure), dehydration, metabolic acidosis, acute kidney failure, or tetany can occur. Death has been reported in infants or adults with oral, rectal, or intravenous phosphates, particularly in those at increased risk for electrolyte disturbances, and in those receiving more than 45 or 90 milliliters in a 24-hour period. Late symptoms may include abdominal pain, vomiting of phosphorescent materials, bloody vomiting and diarrhea, headache, limb aches, tongue coating, foul breath, weakness, yellow conjunctivae (whites of the eyes). Rare complications may include confusion, convulsions (seizures), headache, dizziness, numbness, tingling, pain, weakness, anxiety, increased thirst, muscle cramps, or fatigue. Abnormal heart rhythms, shortness of breath, foot/leg swelling, and weight gain have been reported.Management of toxicitymay include sulfate of copper emetic, or lavage with Epsom salts in water (repeated every hour); repeated small doses of sulfate of copper and large doses of bicarbonate of soda. Oxygen inhalation, external heat, camphor, old oil of turpentine, and permanganate of potassium have been recommended.
http://www.enotalone.com/article/9375.html
http://www.labtestsonline.org/understanding/analytes/phosphorus/test.html
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