Alternative Names: ALB; Albumin, Serum; Albumin, Plasma

Test Code: 1ALB

Clinical Significance: Albumin is a carbohydrate-free protein, which constitutes 55-65 % of total plasma protein. It maintains plasma oncotic pressure and is also involved in the transport and storage of a wide variety of ligands and is a source of endogenous amino acids. Albumin binds and solubilizes various compounds, e.g., bilirubin, calcium, and long-chain fatty acids. Furthermore, albumin is capable of binding toxic heavy metal ions as well as numerous pharmaceuticals, which is the reason why lower albumin concentrations in blood have a significant effect on pharmacokinetics.

Hyperalbuminemia is of little diagnostic significance except in the case of dehydration. Hypoalbuminemia occurs during many illnesses and is caused by several factors: compromised synthesis due either to liver disease or because of reduced protein uptake; elevated catabolism due to tissue damage (severe burns) or inflammation; malabsorption of amino acids (Crohn’s disease); proteinuria because of nephrotic syndrome; protein loss via the stool (neoplastic disease). In severe cases of hypoalbuminemia, the maximum albumin concentration of plasma is 2.5 g/dL (380 µmol/L). Due to the low osmotic pressure of the plasma, water permeates through blood capillaries into tissue (edema). The determination of albumin allows monitoring of a controlled patient dietary supplementation and serves also as an excellent test of liver function.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium Heparin PST

Alternative Specimen Type: Serum or K-2 EDTA Plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
· Refrigerated: 5 months
· Frozen: 4 months

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 3.5 to 5.2 g/dL

CPT: 82040

Test Principle: Colorimetric assay using a Roche Cobas c501 test module.

Specimen Retention: 7 days

Alternative Names: ALP; Alkaline Phosphatase, total

Test Code: 1ALP

Clinical Significance: Alkaline phosphatase in serum consists of four structural genotypes: the liver bone kidney type, the intestinal type, the placental type, and the variant from the germ cells. It occurs in osteoblasts, hepatocytes, leukocytes, the kidneys, spleen, placenta, prostate, and the small intestine. The liver bone kidney type is particularly important. A rise in the alkaline phosphatase occurs with all forms of cholestasis, particularly with obstructive jaundice. It is also elevated in diseases of the skeletal system, such as Paget’s disease, hyperparathyroidism, rickets and osteomalacia, as well as with fractures and malignant tumors. A considerable rise in the alkaline phosphatase activity is sometimes seen in children and juveniles. It is caused by increased osteoblast activity following accelerated bone growth.

Turnaround Time: 24 hours
Preferred Specimen Type: Lithium Heparin PST
Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 2 months
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s):
Male (≥18 years): 40 to 129 U/L
Female (≥18 years): 35 to 104 U/L

CPT: 84075

Test Principle: Colorimetric assay using a Roche Cobas c501 test module.

Specimen Retention: 7 days

Alternative Names: ALT; GPT; SGPT; Transaminase, SGPT

Test Code: 1ALT

Clinical Significance: The enzyme alanine aminotransferase (ALT) has been widely reported as present in a variety of tissues. The major source of ALT is the liver, which has led to the measurement of ALT activity for the diagnosis of hepatic diseases. Elevated serum ALT is found in hepatitis, cirrhosis, obstructive jaundice, carcinoma of the liver, and chronic alcohol abuse. ALT is only slightly elevated in patients who have an uncomplicated myocardial infarction.

Although both serum aspartate aminotransferase (AST) and ALT become elevated whenever disease processes affect liver cell integrity, ALT is the more liver-specific enzyme. Moreover, elevations of ALT activity persist longer than elevations of AST activity.

In patients with vitamin B6 deficiency, serum aminotransferase activity may be decreased. The apparent reduction in aminotransferase activity may be related to decreased pyridoxal phosphate, the prosthetic group for aminotransferases, resulting in an increase in the ratio of apoenzyme to holoenzyme.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum or K-2 EDTA Plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated:7 days
Frozen: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s):
Male (≥18 years): 0 to 41 U/L
Female (≥18 years): 0 to 33 U/L

CPT: 84460

Test Principle: Testing is performed on a Roche Cobas c501 module. ALT catalyzes the reaction between L-alanine and 2-oxoglutarate. The pyruvate formed is reduced by NADH in a reaction catalyzed by lactate dehydrogenase (LDH) to form L-lactate and NAD+. The rate of the NADH oxidation is directly proportional to the catalytic ALT activity. It is determined by measuring the decrease in absorbance.

Specimen Retention: 7 days

Alternative Names: alpha-amylase

Test Code: 1AMYL

Clinical Significance: The α-amylases (1,4-α-D-glucanohydrolases, EC 3.2.1.1) catalyze the hydrolytic degradation of polymeric carbohydrates such as amylose, amylopectin, and glycogen by cleaving 1,4-α-glucosidic bonds. In polysaccharides and oligosaccharides, several glycosidic bonds are hydrolyzed simultaneously. Maltotriose, the smallest such unit, is converted into maltose and glucose, albeit very slowly. Two types of α-amylases can be distinguished, the pancreatic type (P-type) and the salivary type (S-type). Whereas the P-type can be attributed almost exclusively to the pancreas and is therefore organ-specific, the S-type can originate from several sites. As well as appearing in the salivary glands it can also be found in tears, sweat, human milk, amniotic fluid, the lungs, testes, and the epithelium of the fallopian tube.

Because of the sparsity of specific clinical symptoms of pancreatic diseases, α-amylase determinations are of considerable importance in pancreatic diagnostics. They are mainly used in the diagnosis and monitoring of acute pancreatitis. Hyperamylasemia does not, however, only occur with acute pancreatitis or in the inflammatory phase of chronic pancreatitis, but also in renal failure (reduced glomerular filtration), tumors of the lungs or ovaries, pulmonary inflammation, diseases of the salivary gland, diabetic ketoacidosis, cerebral trauma, surgical interventions or in the case of macroamylasemia. To confirm pancreatic specificity, it is recommended that an additional pancreas-specific enzyme - lipase or pancreatic-α-amylase - also be determined.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated (preferred): 30 days
Frozen: 30 days
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 28 to 100 U/L

CPT: 84075

Test Principle: Enzymatic colorimetric assay performed on a Roche Cobas c501 module.
Specimen Retention: 7 days

Alternative Names: AST; GOT; SGOT; Transaminase, SGOT

Test Code: 1AST

Clinical Significance: The enzyme aspartate aminotransferase (AST) is widely distributed in tissue, principally hepatic, cardiac, muscle, and kidney. Elevated serum levels are found in diseases involving these tissues. Hepatobiliary diseases, such as cirrhosis, metastatic carcinoma, and viral hepatitis also increase serum AST levels. Following myocardial infarction, serum AST is elevated and reaches a peak 2 days after onset.

In patients undergoing renal dialysis or those with vitamin B6 deficiency, serum AST may be decreased. The apparent reduction in AST may be related to decreased pyridoxal phosphate, the prosthetic group for AST, resulting in an increase in the ratio of apoenzyme to holoenzyme.
2 isoenzymes of AST have been detected, cytoplasmic and mitochondrial. Only the cytoplasmic isoenzyme occurs in normal serum, while the mitochondrial, together with the cytoplasmic isoenzyme, has been detected in the serum of patients with coronary and hepatobiliary disease.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum; K-2 EDTA plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated (preferred): 7 days
Frozen: 3 months
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Reference Interval(s):
Male (≥18 years): 0 to 40 U/L
Female (≥18 years): 0 to 32 U/L

CPT: 84450

Test Principle: Testing is performed on the Roche c501 test module. AST in the sample catalyzes the transfer of an amino group between L-aspartate and 2oxoglutarate to form oxaloacetate and L-glutamate. The oxaloacetate then reacts with NADH, in the presence of malate dehydrogenase (MDH), to form NAD+. The rate of NADH oxidation is directly proportional to the catalytic AST activity. It is determined by measuring the decrease in absorbance.

Specimen Retention: 7 days

Alternative Names: DBILI; Conjugated Bilirubin

Test Code: 1DBILI

Clinical Significance: Bilirubin is an organic compound formed by the reticuloendothelial system during the normal and abnormal destruction of red blood cells. Measurements of bilirubin are used in the diagnosis of liver disease, in the detection of hemolytic anemia, and to evaluate degrees of jaundice.
Since the introduction of the diazo method for bilirubin determination by Ehrlich in 18831, several modifications have been proposed to enhance the reaction. The Evelyn-Malloy method2 employs methanol to catalyze the azo-coupling reaction of the indirect bilirubin, as well as to keep the azobilirubin in solution. A serious disadvantage of this method lies in the fact that protein may be precipitated by the methanol solution to yield falsely lowered results.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.
4. Samples should be protected from light.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 6 months
Ambient: 2 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.
· Specimens collected in anticoagulants other than lithium heparin.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 0 to 0.3 mg/dL

CPT: 82248

Test Principle: Testing is performed using the Roche c501 test module. Acidified sodium nitrite produces nitrous acid, which reacts with sulfanilic acid (in acidic solution) to form a diazonium salt. The diazotized sulfanilic acid then reacts with bilirubin to form isomers of azobilirubin. In the direct bilirubin assay, only conjugated bilirubin is converted by the diazotized sulfanilic acid. The intensity of the red color of azobilirubin is measured photometrically and is proportional to the direct (conjugated) bilirubin concentration. This assay is performed on a Roche Cobas c501 module.

Specimen Retention: 7 days

Alternative Names: TBILI

Test Code: 1TBILI

Clinical Significance: Measurement of the levels of bilirubin, an organic compound formed during the normal and abnormal destruction of red blood cells, is used in the diagnosis and treatment of liver, hemolytic, hematological, and metabolic disorders, including hepatitis and gall bladder blockage.

Bilirubin is formed in the reticuloendothelial system during the degradation of aged erythrocytes. The heme portion from hemoglobin and from other heme-containing proteins is removed, metabolized to bilirubin, and transported as a complex with serum albumin to the liver. In the liver, bilirubin is conjugated with glucuronic acid for solubilization and subsequent transport through the bile duct and elimination via the digestive tract.

Diseases or conditions which, through hemolytic processes, produce bilirubin faster than the liver can metabolize it, cause the levels of unconjugated (indirect) bilirubin to increase in the circulation. Liver immaturity and several other diseases in which the bilirubin conjugation mechanism is impaired cause similar elevations of circulating unconjugated bilirubin. Bile duct obstruction or damage to hepatocellular structure causes increases in the levels of both conjugated (direct) and unconjugated (indirect) bilirubin in the circulation.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum, K2-EDTA plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.
4. Specimens must be protected from light.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 6 months
Ambient: 24 hours

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 0 to 1.2 mg/dL

CPT: 82247

Test Principle: Colorimetric diazo method. Total bilirubin, in the presence of a suitable solubilizing agent, is coupled with 3,5-dichlorophenyl diazonium in a strongly acidic medium. The color intensity of the red azo dye formed is directly proportional to the total bilirubin and can be determined photometrically. This assay is measured using a Roche Cobas c501 module.

Specimen Retention: 7 days

Alternative Names: Urea

Test Code: 1URE

Clinical Significance: Urea is the major end product of protein nitrogen metabolism. It is synthesized by the urea cycle in the liver from ammonia which is produced by amino acid deamination. Urea is excreted mostly by the kidneys, but minimal amounts are also excreted in sweat and degraded in the intestines by bacterial action. Determination of blood urea nitrogen is the most widely used screening test for renal function. When used in conjunction with serum creatinine determinations it can aid in the differential diagnosis of the three types of azotemia: prerenal, renal and postrenal.

Elevations in blood urea nitrogen concentration are seen in inadequate renal perfusion, shock, diminished blood volume (prerenal causes), chronic nephritis, nephrosclerosis, tubular necrosis, glomerular nephritis (renal causes) and urinary tract obstruction (postrenal causes). Transient elevations may also be seen during periods of high protein intake. Unpredictable levels occur with liver diseases.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum; K2-EDTA plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 12 months
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 6 to 20 mg/dL
Critical Value: >130 mg/dL

CPT: 84520

Test Principle: Kinetic test with urease and glutamate dehydrogenase. 2,3,4,5 Urea is hydrolyzed by urease to form ammonium and carbonate. In the second reaction 2oxoglutarate reacts with ammonium in the presence of glutamate dehydrogenase (GLDH) and the coenzyme NADH to produce L-glutamate. In this reaction two moles of NADH are oxidized to NAD+ for each mole of urea hydrolyzed. The rate of decrease in the NADH concentration is directly proportional to the urea concentration in the specimen and is measured photometrically. This assay is performed on a Roche Cobas c501 module.

Specimen Retention: 7 days

Alternative Names: Ca; Calcium, total

Test Code: 1CA

Clinical Significance: Calcium is the most abundant mineral element in the body with about 99 percent in the bones primarily as hydroxyapatite. The remaining calcium is distributed between the various tissues and the extracellular fluids where it performs a vital role for many life-sustaining processes. Among the extra skeletal functions of calcium are involvement in blood coagulation, neuromuscular conduction, excitability of skeletal and cardiac muscle, enzyme activation, and the preservation of cell membrane integrity and permeability.

Serum calcium levels and hence the body content is controlled by parathyroid hormone (PTH), calcitonin, and vitamin D. An imbalance in any of these modulators leads to alterations of the body and serum calcium levels. Increases in serum PTH or vitamin D are usually associated with hypercalcemia. Increased serum calcium levels may also be observed in multiple myeloma and other neoplastic diseases. Hypocalcemia may be observed e.g., in hypoparathyroidism, nephrosis, and pancreatitis.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 3 weeks
Frozen: 8 months
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.
· Samples collected in anticoagulants other than lithium heparin.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 8.6 to 10.0 mg/dL

Critical Values: <7.0 or >13.0 mg/dL

CPT: 82330

Test Principle: Calcium ions react with 5nitro5’methylBAPTA (NM-BAPTA) under alkaline conditions to form a complex. This complex reacts in the second step with EDTA. The change in absorbance is directly proportional to the calcium concentration and is measured photometrically. This assay is measured using the Roche c501 test module.

Specimen Retention: 7 days

Alternative Names: Cl; Chloride, serum or plasma

Test Code: 1CL

Clinical Significance: is the major extracellular anion and serves to regulate the balance of extracellular fluid distribution. Similarly to the other ions, common causes of decreased chloride include reduced dietary intake, prolonged vomiting and reduced renal reabsorption as well as some forms of acidosis and alkalosis. Increased chloride values are found in dehydration, kidney failure, some forms of acidosis, high dietary or parenteral chloride intake, and salicylate poisoning.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.25 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 30 days
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Gross lipemia
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.
· Samples collected using any other anticoagulant than Lithium heparin.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 98 to 107 mmol/L

Critical Value: <80 mmol/L

CPT: 82435

Test Principle: The complete measurement system for a particular ion includes the ISE, a reference electrode, and electronic circuits to measure and process the EMF to give the test ion concentration.
The sodium and potassium electrodes are based on neutral carriers and the chloride electrode is based on an ion exchanger. Testing is performed using a Roche c501 test module.

Specimen Retention: 7 days

Alternative Names: Cholesterol, total

Test Code: 1CHOL

Clinical Significance: Cholesterol is a steroid with a secondary hydroxyl group in the C3 position. It is synthesized in many types of tissue, but particularly in the liver and intestinal wall. Approximately three quarters of cholesterol is newly synthesized, and a quarter originates from dietary intake. Cholesterol assays are used for screening for atherosclerotic risk and in the diagnosis and treatment of disorders involving elevated cholesterol levels as well as lipid and lipoprotein metabolic disorders.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum; K2-EDTA plasma

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Patient Preparation: Fasting is preferred.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 3 months
Ambient: 7 days

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 0 to 199 mg/dL

CPT: 82465

Test Principle: Enzymatic, colorimetric method using the Roche c501 test module.

Cholesterol esters are cleaved by the action of cholesterol esterase to yield free cholesterol and fatty acids. Cholesterol oxidase then catalyzes the oxidation of cholesterol to cholest-4-en-3-one and hydrogen peroxide. In the presence of peroxidase, the hydrogen peroxide formed effects the oxidative coupling of phenol and 4-aminophenazone to form a red quinone-imine dye. The color intensity of the dye formed is directly proportional to the cholesterol concentration. It is determined by measuring the increase in absorbance.

Specimen Retention: 7 days

Alternative Names: Bicarb; Bicarbonate; HCO3

Test Code: 1CO2

Clinical Significance: Bicarbonate is the second largest fraction of the anions in plasma. Included in this fraction are the bicarbonate (HCO3-) and carbonate (CO32-) ions, as well as the carbamino compounds. At the physiological pH of blood, the concentration of carbonate is 1/1000 that of bicarbonate. The carbamino compounds are also present in such low quantities that they are generally not mentioned specifically.
Together with pH determination, bicarbonate measurements are used in the diagnosis and treatment of numerous potentially serious disorders associated with acid-base imbalance in the respiratory and metabolic systems.

Turnaround Time: 24 hours

Preferred Specimen Type: Lithium heparin PST

Alternative Specimen Type: Serum

Specimen Handling:
1. Tubes containing gel should be centrifuged within 2 hours of collection.
2. Tubes that do not contain gel should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection. Vials must be capped immediately as exposure to ambient air can falsely decrease the result of this assay.
3. Store specimens at 2 to 8° C until they are ready to be shipped.

Minimum Volume: 0.5 mL

Specimen Stability:
Refrigerated: 7 days
Frozen: 6 months
Ambient: 40 hours

Rejection Criteria:
· Gross hemolysis
· Any specimen that is received uncentrifuged.
· Any specimen that is received unlabeled.

Specimen Transportation: Specimens should be transported to the laboratory in insulated mailers that contain at least two ice packs.

Reference Interval(s): 22 to 29 mmol/L

Critical Value: <10 mmol/L

CPT: 82374

Test Principle: Photometric rate reaction. Bicarbonate reacts with phosphoenolpyruvate (PEP) in the presence of PEPC to produce oxaloacetate and phosphate. The reaction is coupled with one involving the transfer of a hydrogen ion from NADH analog to oxaloacetate using MDH. The resultant consumption of NADH analog causes a decrease in absorbance, which is proportional to the concentration of bicarbonate in the sample being assayed. Testing is performed using a Roche Cobas c501 module.

Specimen Retention: 7 days; however, this assay cannot be added onto samples that were uncapped greater than one hour.