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phosphorus (inorganic phosphate) in serum
Reference values:
- Male: 2.5- 4.5 mg/dL, 0.83-1.5 mmol/L
- Female: 2.5- 4.5 mg/dL
Conversion factor: mg/dL -> mmol/L is 0.33
Clinical significance:
Phosphorus, as phosphate, has an ubiquitous distribution in the body. Most inorganic phosphate in the body is intracellular. Thus serum phosphorus concentration does not necessarily reflect total body phosphorous stores.
Serum phosphorous concentrations have a circadian rhythm, highest in the late morning, lowest in the evening. Serum levels are subject to rapid variation secondary to environmental changes. There is a seasonal variation with maximum levels in May & June & lowest levels in winter. Bed rest causes an increase in up to 0.5 mg/dL.
Increases:
1) dehydration
2) hypoparathyroidism
3) hypervitaminosis D
4) osteolytic metastases to bone
5) sarcoidosis
6) pulmonary embolism
7) renal failure
8) diabetes mellitus with ketosis
9) myelogenous leukemia
10) milk-alkali syndrome
11) healing fractures
12) acromegaly
13) portal cirrhosis
14) lactic acidosis
15) respiratory acidosis
16) drugs
a) androgens
b) beta-blockers
c) ethanol
d) ergocalciferol
e) furosemide
f) growth hormone
g) hydrochlorothiazide
h) methicillin (occurs with nephrotoxicity)
i) phosphates
j) etidronate
k) tetracycline (occurs with nephrotoxicity)
Decreases:
1) causes of serum Ca+2 elevation
a) primary hyperparathyroidism
b) PTH-producing tumor
c) familial hypocalciuric hypercalcemia
2) sepsis (gram-negative)
3) vitamin D deficiency
4) renal tubular disorders (Fanconi syndrome)
5) chronic hemodialysis
6) vomiting & nasogastric suction
7) decreased dietary phosphate intake (occasional)
8) malabsorption & steatorrhea
9) osteomalacia
10) hypokalemia
11) acute gout
12) respiratory tract infection
13) respiratory alkalosis
14) osteoblastic metastases
15) diuretic phase of severe burns
16) drugs
a) aluminum-containing antiacids
b) acetazolamide
c) albuterol
d) amino acids
e) anesthetic agents
f) calcitonin
g) carbamazepine
h) epinephrine
i) estramustine
j) estrogens
k) fructose
l) glucocorticoids
m) glucose
n) hydrochlorothiazide (prolonged treatment)
o) ifosfamide
p) insulin
q) isoniazid
r) oral contraceptives
s) phenytoin
t) salicylate poisoning
u) sucralfate
Interferences: (chemical interferences)
1) resulting in high values:
a) bilirubin
b) detergents
c) fat emulsions
d) hemoglobin
e) lipemia
f) methotrexate
2) resulting in low values:
a) citrates
b) mannitol
c) oxalate
d) tartrates
e) phenothiazines
Principle:
The Kodak Ektachem Clinical Chemistry Slide (PHOS) is a dry, multilayered analytical element coated on a clear polyester support.The analysis is based on the reaction of inorganic phosphate with ammonium molybdate to form an ammonium phosphomolybdate complex at acidic pH, as described by Fiske & Subbarow. p-Methylaminophenol sulfate, an organic reductant reported by Gomori, reduces the complex to form a stable heteropolymolybdenum blue chromophore.
The National Committee for Clinical Laboratory Standards identifies this method as preferred 'methodological principle' for the determination of serum inorganic phosphorus.
A 10 microliter drop of patient sample is deposited on the slide and is evenly distributed by the spreading layer. Phosphorus in the specimen forms a complex with ammonium molybdate. This complex is reduced by p-methylaminophenol sulfate to give a blue complex.
The concentration of phosphorus in the sample is determined by measuring the heteropolymolybdenum blue complex by reflectance spectrophotometry.
Specimen:
No special patient preparation is necessary.
Sample Preparation: Collect the specimen by the standard venipuncture technique. Lithium or sodium heparin may be used as an anticoagulant for plasma specimens. Sodium fluoride/potassium oxalate, citrate, & EDTA should not be used as anticoagulants. Remove serum or plasma promptly from clot or cells. Handle specimens in stoppered containers to avoid contamination & evaporation. Refrigerate specimens at 2-8 degrees Celsius if analysis is not performed within four hours. Freeze specimens at -18 degrees Celsius if analysis is delayed beyond 48 hours.
Sample requirements: Minimum- 0.5 mL serum or plasma. Optimum- 1.0 mL serum or plasma.
Related
calcium phosphate product (Ca-P product)
hyperphosphatemia
hypophosphatemia
inorganic phosphate; inorganic phosphorous
General
phosphorus (inorganic phosphate) in body fluid
References
- Kodak Ektachem 700 Test Methodologies Manual, Kodak Clinical
Products, Rochester, N.Y., 1990.
- Kodak Ektachem 700 Operators Manual, Kodak Clinical Products,
Rochester, N.Y., 1987.
- Package Insert, Kodak Ektachem Special Calibrators, Kodak
Clinical Products, Rochester, N.Y., 1985.
- Package Insert, Bio-Rad Liquichek Controls, Bio-Rad ECS
Division, Anaheim, CA., 1992.
- Guide to Clinical Laboratory Tests, 3rd ed, NW Teitz (ed)
WB Saunders, 1995.
- Clinical Diagnosis & Management by Laboratory Methods,
19th edition, J.B. Henry (ed), W.B. Saunders Co.,
Philadelphia, PA. 1996, pg 11.
- Phosphorus, Inorganic, Serum or Plasma
Laboratory Test Directory ARUP: 20028
- Panel of 11 tests
Laboratory Test Directory ARUP: 20144
Component-of
bone/joint panel
calcium/phosphate in serum/plasma
chronic kidney disease panel
enteral/parenteral nutrition management panel
parathyroid panel
renal function tests; renal function panel