CALCIUM, SERUM, PLASMA
|In House Availability||Routine: 7 days.
STAT: 24 hours/7 days.
|Principle||Analysis is based on the reaction of calcium with an indicator dye (o-cresolphthalein complexone) to form a colored complex.|
1. Routine calcium: (serum and urine): diagnosis and management of bone metabolism and calcium dysregulation disorders; cancer screening.
2. Stat calcium: acute seizure activity, acute altered mental status, tetany, pre/post-dialysis, acute arrhythmia, prolonged or shortened QT interval on cardiogram.
1. Serum increased: hyperparathyroidism, vitamin D intoxication, cancer, acute osteoporosis, Burnett's syndrome, idiopathic in infants, infantile hypophosphatasia, berylliosis, hyperthyroidism, hyperproteinemia (i.e., multiple myeloma, sarcoid, collection conditions [tourniquet], oral contraceptives, Ca++ salts).
2. Serum decreased: hypoparathyroidism, malabsorption, hypoalbuminemia of any etiology, CRF with phosphate retention, acute pancreatitis, insufficient ingestion of calcium, phosphate, or vitamin D, osteomalacia, rickets, starvation, late pregnancy.
|Container type||gel tube (gold or green top)|
|Amount to Collect||2 mL|
|Special instructions||Fasting sample.
Note: Anticoagulants such as EDTA, oxalate & citrate bind calcium and will lead to spuriously low results. Heparinized tubes (green-top) may be used for stats.
All values less than 6.5 mg/dL (< 1.62 mmol/L) or greater than 13.5 mg/dL (> 3.37 mmol/L) are considered Critical Values and are called to the physician or patient care unit immediately.
(Ionized fraction varies with serum protein concentration, and especially the albumin content of serum).
|Synonyms||Metabolic Basic Panel (METB): NA, K, CL, CO2, CREA, BUN, GLUC, CA;|
|Stability||Serum calcium is stable at 4°C for 2-3 days; at -20°C for 6 months.|
|Interferences||Many drugs can increase or decrease serum and urine calcium. If you have any question, please contact the Laboratory Medicine Resident in Clinical Chemistry (x65527, or pager (415) 443-2311).
1. Decrease: fluoride, anticoagulants, glucose infusion, gadolinium dye.
2. Increase: bed rest, diurnal variation, tourniquet.
a See also: Young, D.S. (Reference #2.)
|References||1. Gitelman, H.J.: An improved automated procedure for the determination of calcium in biochemical specimen. Anal Biochem 18:521-531, 1967.
2. Young DS. Effects of Drugs on Clinical Laboratory Tests ed. 4. Washington D.C.: AACC Press; 1995.
3. Bayer(TM) Clinical Methods Calcium (39) B01-4145-01 Advia 1650 Operator's Guide. PN 073-5001-09. Last accessed June 2003. Siemens Medical Solutions Diagnostics, Malvern, PA.
4. Kang, HP; Scott, MG; Joe, BN; Narra V; Heiken, J; Parvin, CA. Model for predicting the impact of gadolinium on plasma calcium measured by the o-cresolphthalein method. Clin Chem, 2004; 50:741-746.
5. Brown, JJ; Hynes, MR; Wible, JH. Measurement of serum calcium concentration after administration of four gadolinium-based contrast agents to human volunteers. Am J Roentgenol, 2007; 189:1539-1544.
6. Gandhi, MJ; Narra, VR; Brown, JJ; Guo, A; Scott, G. Impact of falsely decreased calcium values due to gadolinium interference. Clin Chem, 2007; 53:A179.
|Last Updated||6/18/2011 8:28:38 AM|