Chemistry Tests

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Chemistry Tests

General Comments about testing

There are so many different methods used to analyze different chemical compounds that to state one method over another is unfair. Another issue is that your body’ chemistry changes throughout the day in response to external conditions such as exercise and internal conditions such as kidney function. This makes comparisons among various tests difficult to do. One method to lessen these variables is to try to have your tests done by the same laboratory so that comparisons of test values are possible. It is also beneficial then to have your tests drawn under the same conditions (fasting/non fasting, early morning/late afternoon, etc.) so that you can eliminate these interferences when you look at your results. The following list indicates any special preparations and a general sense of for the conditions associated with the tests, and their general reference ranges.

Acid Phosphatase (AcP)

Acid Phosphatase is an enzyme found in prostate and bone. Elevations are found in all prostate disease and after manual examination of the prostate, bone diseases such as Paget’s Disease and some malignancies.

This test can be performed on a patient in either a fasting or non fasting state. The adult reference range is 0 -2.0 IU/L . One of the problems, as with other enzymes, is that there are multiple ways to calculate the values resulting in different types of figures. Acid phosphatase an be separated into various subcategories such as prostatic acid phosphatase, etc. by other tests.

Alanine Aminotransferase (ALT)

Also known by the older terminology, SGPT, this enzyme is used to degrade material in the liver. Elevation in ALT is seen in a wide variety of liver disorders and as a consequence of certain medications which inhibit liver function.

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary widely with different instruments.

Albumin

Assays for serum albumin can be done on both fasting or non fasting specimens. Albumin is made in the liver and is responsible for maintaining proper fluid balances. Too little albumin may result in fluids "leaking" out of the blood vessels into surrounding spaces such as the abdomen. Decreased amounts of albumin can occur when the liver is not making enough or if albumin is being lost through the kidneys. Increases in albumin do not occur naturally but can be seen in patients who had received albumin suspensions. The typical reference range is 2.6 - 5.2 g/dL. with an acceptable variation is 0.5g/dL..

Albumin is the major non-globulin portion of total protein and is used to follow liver function or problems in gastrointestinal tract absorption or kidney disease or to differentiate total protein problems from globulin problems. Pre-albumin is also made by the liver and is active in vitamin A metabolism and in thyroid function.

Alkaline Phosphatase (AlkP)

Alkaline Phosphatase is an enzyme found in bone, liver, intestines and placenta. The total can be subdivided into subcategories that will narrow down the specific site. This test is usually used to follow bone or liver function

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary widely with different instruments.

Aspartate Aminotransferase (AST) old terminology SGOT

Also known by its older name, SGOT, this enzyme is needed in the utilization of energy sources. It is found in high concentrations in muscle (cardiac and others), liver, and other organs. This test usually is ordered to follow cardiac and muscle disease .

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary widely with different instruments.

Bilirubin, Total

Bilirubin is the end product of red cell lysis and recycling of hemoglobin which is performed in the liver. The test quantifies two different forms of bilirubin, one is the final product while the other is an intermediate form.

The build up of bilirubin in the blood stream is called jaundice and is a general sign of liver disease. Many medications, gall bladder disease as well as viruses such as infectious mononucleosis and hepatitis will have jaundice. Many infants are born with less than fully mature livers. As a consequence, for the first several days, they may show "neonatal jaundice" which is a build up of bilirubin in the blood stream. This should go away as the liver matures. Bilirubin determinations are used to study liver function and red cell metabolism

The specimen can be drawn from a patient who is in either the fasting or non fasting (preferred fasting) state. The adult reference ranges 0-1.5mg/dL..

BUN (Blood Urea Nitrogen)

Ammonia is a product of the digestion of protein - containing foods. It is also released during various metabolic reactions in the body. In excess, ammonia is toxic. Normally, the liver converts ammonia to urea which is then excreted by the kidney in the urine. Both serum (the liquid portion of blood after it is allowed to clot) and plasma (the liquid portion of unclotted or whole blood)is the sample of choice. This test does not require any special patient preparation. The adult reference range is 5 - 20 mg/dL. but will vary slightly depending on the testing mechanism. values above 30mg/dL. should be investigated further.

Calcium

Calcium is required for cell function overall and for bone metabolism. Too little calcium gets you either a loss of tissue function or soft bones (osteoporosis) while too much gives you tetni ( cardiac arrest and/or lock jaw is from over clenching of muscles) or over brittle bones. Changes in calcium are used to assess bone function. Higher blood levels usually mean lower bone levels. Usually performed in conjunction with Phosphorous determinations.

This test can be performed on a specimen from a patient in either a fasting or non fasting state. The adult reference ranges are 8.5 - 10.5 mEq/L.

Cholesterol

Cholesterol is a waxy substances used in every cell membrane you have and as a base for several hormones. The recommended daily allowance for dietary cholesterol intake is 300 milligrams. Most cells have some capacity to synthesize cholesterol. The largest percentage of synthesized cholesterol is made in the liver. Cholesterol lowering medications prescribed by physicians inhibit the synthesis of cholesterol by the liver, thereby reducing the level in the blood stream.

The upper limit of acceptability for cholesterol values is 170 mg/dL. for children and below 200 mg/dL. for adults. This does NOT include the whole blood "prick your finger" style of test which have usually higher values. The test can be done on a specimen taken from a patient in either the fasting or non fasting state although the fasting specimen is preferred as no additional lipid studies can be done on a non fasting specimen.

Decreased values in cholesterol are usually due to high cell turnover while increased values are seen in fat rich/unbalanced diet and overproduction by the liver.

Creatinine

Creatinine is the end product of muscle metabolism. It is excreted through the kidneys and changes in creatinine are an early indicator of kidney disease as well as being seen in severe muscle damage or wasting diseases or with many medications such as antibiotics. this test can be performed on specimens drawn from patients in either the fasting or non fasting state.

The adult reference ranges for serum is less than 1.2 mg/dL. although children have a lower level. This is a very consistent test and should vary only by -0.1 mg.

Electrolytes (sodium - potassium - chloride - carbon dioxide) or (Na - K - Cl - CO2)

The term "electrolytes) describes a panel of four tests typically ordered together. These four constituents help to maintain water distribution in tissues, to regulate health and other muscle function, and to regulate body pH. They can be done fasting or non fasting specimens.

The adult reference ranges are:

sodium (Na):

135 - 145

mEq/L

potassium (K):

3.5 - 5.0

"

chloride (Cl):

95 - 105

"

carbon dioxide (CO2):

21 - 28

mmol/L

SODIUM - increases are seen in water loss such as sweating, diarrhea or vomiting, and inadequate water intake. Decreases are seen in taking in too much water, cardiac failure, liver disease, kidney disease and some medications.

POTASSIUM - increases are seen in condition in which there is great tissue damage such as crushing injuries and kidney disease. Some diuretics, such as those of the thiazide group, increase the excretion of potassium by the kidneys. Prolonged use of such drugs may lead to potassium depletion. Patients on diuretic therapy should discuss this issue with their physician.. Most often it is due to hemolysis (the destruction of red cells) which can occur in the patient or as a result of a poor phlebotomy or storage/transport issues. Elevations of serum potassium in the patient can cause severe cardiac distress.

CHLORIDE - increases and decreases in chloride are seen at the same time as increases and decreases in sodium.

CARBON DIOXIDE - increases in carbon dioxide are seen in metabolic alkalosis and other metabolic diseases while decreases are seen in metabolic acidosis conditions such as diabetes.

The following values require immediate attention from a physician:

sodium (Na):

below 120 or above 160

mEq/L

potassium (K):

below 2.5 or above 6.0

"

carbon dioxide (CO2):

below 10 or above 40

mmol/L

This profile is a general reflection of bodily function and metabolic balance. The results can e affected by digestion and absorption of dietary products, kidney function, lung function, and the general health of the patient.

g(gamma) glutamyl transferase

This enzyme used to metabolize materials in the kidney, liver, gall bladder, and pancreas. It is an exceptionally sensitive indicator of stress in these sites. As a consequence, variations in results may be quite common. Alcohol consumption (even a little) and many medications are the chief causes of these swings. This test is used to follow kidney, liver or pancreatic function

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary widely with different instruments.

Globulins - Protein Electrophoresis (SPE)

Globulins are have a wide variety of functions. Similar to the total protein, if a globulin result is unusual, it is important to find out which component is responsible for the change. Globulins are most commonly separated by the use of a technique called electrophoresis. In this process, a collection of proteins are separated by the use of an electrical charge. There are 4 major components of globulins.

alpha-1-globulinsThe major components of alpha-1 globulin is alpha-1-antitrypsin. This is an inhibitor of the enzyme, trypsin. Without adequate amounts, patients can experience pulmonary emphysema. Increased amounts of alpha-1-antitrypsin are seen in inflammation so it is a nonspecific indicator of cellular damage and is not useful to determine what type of inflammation is present.

alpha-2- globulins

HAPTOGLOBIN is the major constituent of alpha-2-globulins. It is responsible for the binding of hemoglobin that is released into the circulation when red cells die. Without it, the reusable portions of the hemoglobin molecule cannot be processed for recycling. Haptoglobin exists as free and bound. Only free haptoglobin is quantified routinely. Increased levels of haptoglobin are seen in stress, inflammation and infections. Since these conditions can be more accurately assessed with other tests, the haptoglobin assayis not performed for these. A decrease in free haptoglobin can mean that either the liver is not making haptoglobin or that there is an increase in red cell death which is causing most/all of the haptoglobin to be bound to the hemoglobin. Free hemoglobin in the plasma is toxic to the kidneys so a lack of haptoglobin can coincide with kidney damage. There are a variety of test principles that can be used to quantify haptoglobin and they are not compatible.

beta-globulins

Beta globulins include the beta lipoproteins transferrin, and complement.

TRANSFERRIN is a the carrier protein for iron in the bloodstream. Transferrin levels are sometime ordered to determine the cause of iron lack or iron overload.

COMPLEMENT is the general term given to a group of 9 compounds which act during inflammation and the immune response. Each of these 9 can be measured.

gamma globulins

The most important one is the gamma globulins which are mostly antibodies. Antibodies come in 5 different categories: IgG, IgD, IgE all have a similar structure; IgA can be thought of as two IgG stuck together by a joiner piece; and IgM which can be thought of as 5 IgG type molecules stuck together by 5 joiners. Since antibodies are specific to certain antigens, one usually tests for the presence of the specific antibody by either quick tests to measure the presence or absence of the antibody in question or by comparing the level of reaction in two different specimens taken approximately 1 month apart. The quick test provides a yes/no answer; the comparison test - called a titer - provides a "how much" or "how well" answer.

Electrophoresis is used to determine if there is an increase or decrease in the overall total of antibody or pieces of antibody. An increase in an single abnormal antibody might be seen in multiple myeloma or Waldenström’s macroglobulinemia.

-reference ranges are

total globulins:

2.0 - 4.0

mg/dL

alpha 1:

0.2 - 0.4

"

alpha 2:

0.5 - 0.9

"

beta:

0.6 - 1.1

"

gamma:

0.7 - 1.7

"

Globulin assay can be done on either a fasting or non fasting specimen although it is preferred to have a fasting specimen or one collected at least 2 hours after a meal.

Glucose

Glucose is a product of carbohydrate metabolism. It provides energy to cells for normal function. In order to be used, glucose must be transported from the plasma (liquid portion of the blood) into each cell across that cell’s membrane. Insulin makes the movement of glucose into the cell possible.

Blood glucose is measure to monitor the status of carbohydrate metabolism and utilization. Glucose can be measured in serum (the liquid portion of blood after it is allowed to clot), plasma (the liquid portion of unclotted or whole blood) or from whole blood (via a finger stick). Specimens collected from a vein (venipuncture) can be collected for serum by using a tube that has a red colored stopper. The tube will have a green stopped if the anticoagulant is heparin and a gray stopper if the preservative is fluoride. The collection tube must contain the patient’s full name, the time of collection and other means of identification such as a hospital ID number. Failure to completely fill out the label will cause the specimen to be discarded and a new one drawn.

If the physician requests a fasting blood glucose (FBS), the patient should fast (no food or beverages) for 10 - 16 hours prior to the time of collection. Typically, this specimen is collected in the morning with the patient is a sitting position as patient position will cause variation in the concentration of a number of compounds. Values will also be altered by recent patient history: black coffee, interfering medications, exercise, pregnancy, nervousness, etc. so each patient’s values are best interpreted in light of the total picture, not just the mathematical answer.

The adult reference range for glucose is 65 - 110 mg/dL.. values below 40mg/dL. or above 500mg/dL. in adults require immediate attention from a physician. In 1997, the American Diabetes Association established new guidelines for use in diagnosing diabetes mellitus. According to these recommendations, diabetes can be diagnosed in any one of the following three ways, confirmed on a different day by any one of the same procedures:

a fasting plasma glucose value of 126mg/dL. or higher (after fasting for at least 8 hours) a casual(random) plasma glucose of 200mg/dL. or higher (taken at any time of the day without regard to the time of the last meal) with the classic diabetes symptoms of increased urination, increased thirst, and unexplained weight loss. an oral glucose tolerance test value of 200mg/dL. or higher in the two hour sample. Specimens drawn 2 hours after eating (post prandial) are expected to be approximately equal to the fasting state.

A single value only tells what the glucose level is at the time the blood is collected; it gives no indication of how well the level is maintained over time.

Heavy Density Lipoprotein (HdL.)

HdL. play an important role in removing cholesterol from storage in the tissues and transporting it to the liver where it is excreted into the fall bladder. HdL.-cholesterol has been called the "good" cholesterol because it functions to lower the level of cholesterol in the body.

The specimen must be drawn from a patient who is in a fasting (minimum 14 hours with no liquids) state. The reference range is unclear without the cholesterol and other values - aim for below 80.

Immunoglobulins

See the introduction under Globulins.

The adult reference ranges are:

IgA:

113 - 563

mg/dL

IgD:

0.5 - 3.0

"

IgE:

0.01 - 0.04

"

IgG:

800 - 1801

"

IgM:

54 - 222

"

IgA is referred to as secretory IgA; it is not essential for life in that approximately 1:300 people have a hereditary deficiency in it. IgG is referred to as long term antibody in that it provides the permanent form of antibody protection. IgM is usually the first type of antibody to be made; it is followed over time by IgG. IgE is also known as allergen; it is responsible for your allergic reactions such as runny nose and watery eyes. IgD’s action is not clearly understood. Because increases or decreases in these values can occur in a variety of situations, the information from the history, physical and other data are needed for proper interpretation.

Iron (Fe)

Iron is required to make hemoglobin for the red cells, myoglobin for muscles and for several essential enzymes. Decreases in iron produce iron deficiency anemia (the number 1 most common anemia is pre-menapausal women in the US),infections, kidney disease and during post surgical repair. Increases in iron are seen in anemia of chronic inflammation, hemochromatosis, other anemias, and some genetic diseases.

The serum iron assay can be done on either a fasting or non fasting specimen, although a fasting specimen is preferred. The adult reference range is 60 - 150 µg/dL.

Lactate Dehydrogenase (LD )

Also known by an older name, LDH, this enzyme is found in every cell of the body and is required for life. Any damage to cells that causes the cell contents to empty into the blood stream will cause elevations. There are different isoenzymes or subunits of LD that are specific for certain organs and the analysis of those gives a more targeted result.

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary widely with different instruments.

Lipid Profile (total cholesterol, HdL.-cholesterol, LdL.-cholesterol, triglycerides)

Lipids are fats. Some beneficial aspects of lipids include the following: energy course, function and structural components of cell membranes, and precursor compound to many important substances such as vitamin D and steroid (sex) hormones.

With evidence of a link between elevated lipids and atherosclerosis (also known as arteriosclerosis or atherothrombosis), there is increase interest from both the medical and lay community in the battery of tests commonly ordered as a lipid profile. Preparation for having blood collected for lipid testing should include a 12-14 hour overnight fast.

See individual tests.

Phosphorous (P)

Phosphorous, in relation to calcium levels, plays a role in cell membrane actions and as an essential part of overall cell metabolism.

In bone as the phosphorous increases, the calcium decreases so both numbers are necessary before a conclusion concerning bone health can be reached. Increases in phosphorous can be seen in Paget’s disease, some malignancies, and in patients with healing bone fractures. Decreases are seen in malabsorption, large amounts of alcohol consumption, and some medications such as oral contraceptives, anti convulsants, and antacids.

This test can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference range is 2.0 - 5.0 mg/dL..

Total Protein

A Total Protein can be done on either a fasting or non fasting specimen. It is usually done as a general screening assay since it is composed of two major fractions (albumin and globulin). Elevations or decreases in a total protein must be investigated to find out which of the two components is causing the problem. Since many of the next level tests may be reported as percentages or ratios, it is necessary to have the total protein rerun at the time these tests are performed. Overall, a general reference range is 5.0 - 8.0 gram/dL.. Since this is a stable assay, the range of variation is quite small. Acceptable variation is 1.0

If both the albumin and globulin are elevated, one possibility is dehydration or a slow down of blood flow. If both are decreased, the most common culprit is liver function. Since both albumin and globulin can be assayed individually, they are sometimes reported as an "AG ratio". (See albumin and globulin for specifics.)

Patients with Waldenström’s macroglobulinemia may have total proteins above 8.5. They should consider having tests performed on urine specimens as this will lessen the clotting problem found in the specimen but still provide adequate answers to the physician.

Triglycerides

Most of the fat in our diet is in the form triglycerides and stored body fat is predominantly triglycerides. Plant triglycerides (corn, sunflower, and safflower oils) are polyunsaturated fats while animal fats are saturated fats.

Levels of triglycerides should be below 250 mg/dL..

Thyroid Profile

The thyroid gland produces two hormones thyroxine (T4) and triiodothyronine (T3). these hormones influence many normal bodily functions, including oxygen utilization, heart rate, protein synthesis, carbohydrate metabolism, as well as production and breakdown of cholesterol and triglycerides.

The production of thyroid hormones is controlled by a hormone from the pituitary gland called the thyroid stimulating hormone (TSH). TSH measurement provides information about the two-way communication between the pituitary gland and the thyroid gland. TSH is the initial test ordered when assessing thyroid function. Increased levels of TSH are associated with hypothyroidism and decreased levels are associated with hyperthyroidism.

These tests can be performed on specimens from patients who are either in a fasting or non fasting. Adult reference ranges vary with different instruments.

Uric Acid

Uric acid is one of the constituents of the BUN. It is separated out because it reflects nuclear metabolism over general cellular metabolism. It is the most variable constituent of the BUN due to diet. Increased levels are seen in kidney disease, some malignancies, liver disease, alcohol consumption, and most medications used against malignancies. Decreased levels are considered to be not clinically significant.

These tests can be performed on specimens from patients who are either in a fasting or non fasting, although a specimen from a fasting patient is perferred. In either situations, the patient must not eat a high nuclear content meal such as organ meat for at least 48 hours prior to the specimen collection. There are several different methods for determining uric acid so a single reference range is not psosible.

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