Routine Laboratory Tests
Laboratory tests are used to determine whether there is major abnormality of organ function. For instance, liver enzymes do not go up until approximately 80% of the liver cells are damaged. Standard laboratory tests show when organs are failing, but are not very good at determining whether an organ is functioning at less than top capacity.
Laboratory tests are valuable to the extent that they help us determine whether there are measurements outside the reference range. The reference range is generally considered to be values obtained from 95% of the population without overt disease. This range is based on the assumption that the population overall falls within a bell-shaped curve for all values tested, and statistically that anyone within 2 standard deviations of the mean is "normal". It is possible to be perfectly healthy, and fall outside the reference range. It is also possible to be especially unhealthy and still fall within the reference range.
Routine lab tests are based on absolute values, not taking into account any population variability or genetic differences. The reference range does not generally take into account so-called "functional" illness – of the "I don't feel good but the doctor says there is nothing wrong with me" variety.
CBC – complete blood count – this test measures major parameters of the blood, the white cells, the red cells and the platelets.
White blood cells – WBC – total white cell count is increased with infection or with certain blood cancers like leukemia. Low white cell count can be associated with viral infection, immunodeficiency or other blood diseases.
Hemoglobin/hematocrit – Hgb/Hct – hemoglobin is a measure of the amount of oxygen-carrying protein in the red cell. Hematocrit is the percentage of blood volume occupied by red cells.
Platelet – Plt – platelets initiate the clotting process within the blood vessels. Very low platelets levels lead to spontaneous bruising and bleeding.
Electrolytes include potassium, sodium, chloride and carbon dioxide.
Potassium relates to both skeletal and heart muscle function. Levels inside the cell are much higher than levels in the blood. Any deviation – high or low – from the reference range needs to be evaluated, especially if you are on a diuretic (water pill) or heart medicine.
Sodium is the major electrolyte in the blood. About 10% of people have high blood pressure responsive to sodium restriction. High sodium is generally caused by water restriction or dehydration. Low sodium occurs because of excessive water intake, excessive sodium excretion (with diuretics), very high blood sugar, diabetes drugs or severe liver disease.
Chloride serves as an electrically charged buffer particle, to make sure that the blood acidity stays within a very narrow range. Chloride helps to push bromine ions out of the body (when iodine intake is increased).
Carbon dioxide CO2 also serves the function of regulating the acidity of the blood. Low CO2 may be due to hyperventilation because of excessive production of acid (as in severe diabetes or kidney disease. High CO2 may be due to retention, as in emphysema.
Waste products include BUN and creatinine
BUN, or blood urea nitrogen, is produced by the liver and excreted by the kidneys. With severe liver disease, the BUN becomes very low. With kidney failure, the BUN rises.
Creatinine is produced from muscle break-down, and is excreted by the kidneys. With kidney failure, creatinine rises.
Metabolic syndrome tests
Glucose is the measurement of the blood content of the body's major metabolic fuel. This level may be elevated if you have eating a few hours before the blood was drawn, or if you have diabetes or insulin resistance – the so-called "metabolic syndrome". Fasting glucose levels over 126 indicate a diagnosis of diabetes. Fasting glucose levels over 100 indicate a diagnosis of pre-diabetes, or insulin resistance.
Insulin measures the amount of insulin hormone in the blood. Insulin, produced by the pancreas, is required for the body to utilize glucose. People with type II diabetes have insulin resistance, with high blood insulin and glucose levels. People with type I diabetes have poor insulin production, with low blood insulin and high blood glucose levels.
Glycohemoglobin – Hgb A1C – gives a rough indication of the average blood sugar levels in the red blood cells over the previous 6-8 weeks. Anything over 6.1 is considered to show poor blood sugar control in diabetic patients.
Enzymes include AST, ALT, SGOT, SGPT, and GGT and Alk Phos.
Enzymes are proteins which help chemical reactions take place more quickly at body temperature. They are produced by the liver, by skeletal muscle and by heart muscle, and are released into the blood stream when there is injury or disease of these tissues.
Alk Phos (alkaline phosphatase) is produced by bone and liver. High levels need to be further tested to determine whether the origin is bone or liver. Diseases of the bone like Paget's disease or multiple myeloma may result in very high levels of alk phos.
GGT, gamma-glutamyl transferase, may be elevated with liver disease, lupus, congestive heart failure, and certain drugs.
AST/SGOT and ALT/SGPT are also enzymes produced by liver and muscle. They may be elevated with liver disease or muscle injury.
LDH is produced by almost every cell in the body. It is a measure of cell function, and is the major detoxifier of lactic acid, produced as a waste product of cellular metabolism.
Bilirubin is produced by the liver, as an end-product of the break-down of hemoglobin. It may be elevated with increased breakdown of red blood cells (as in lead poisoning, iron or B12 deficiency, or disorders of the red cell membrane (sickle cell anemia, thalassemis, etc), or with decreased delivery of blood to the liver (as with congestive heart failure or cirrhosis). It may be very elevated in infants who are unable to process it because of immaturity of the liver.
CPK (creatine phosphokinase) may be elevated with skeletal muscle or heart muscle injury.
Albumin and globulin measure types of protein in the blood. Albumin is produced by the liver, and levels are affected by the patient's nutritional status, thyroid hormone levels, cortisol levels, exposure to toxins, and presence of liver disease. Globulin is part of the hemoglobin molecule. Levels are affected by diseases which affect hemoglobin levels. Globulins are also produced by the immune system in response to various foreign substances.
Lipid profile – blood fats
Cholesterol is a steroid hormone produced by the liver. It serves in the cell wall to give it structure and strength – too much cholesterol makes for stiff cell walls. It serves as the precursor to all the sex hormones and the adrenal hormone cortisol. Too little cholesterol makes for low sex drive and low ability to withstand stress. Cholesterol is the molecular equivalent of a BandAid for blood vessels injured from the inside. The cholesterol itself is very helpful, but when this cholesterol BandAid becomes calcified and stiff, then we see the development of vascular disease, heart disease, poor circulation, strokes, etc.
High levels of circulating cholesterol turn of an enzyme called HMG CoA, thus turning off the cell's ability to produce cholesterol.
There are three types of cholesterol – HDL, LDL and VLDL.
HDL – high density lipoprotein – is associated with low levels of heart disease. HDL helps to transport cholesterol to the liver, removing it from the blood stream.
Triglycerides – are fats in the blood, derived from fats, alcohol and sugars or carbohydrates in the diet. These fats serve as building blocks for the manufacture of the cell wall. Foods high in glycemic index stimulate production of triglycerides.
LDL cholesterol – low density lipoprotein – is associated with deposition of cholesterol into the arterial walls, and increased incidence of heart disease. The low density lipoprotein is not as soluble in water or plasma, and is therefore not transported to the liver as readily as the high density lipoproteins.
VLDL cholesterol – very low density lipoprotein – is the form of lipoprotein associated with high levels of triglycerides, and high risk of heart disease. Foods high in glycemic index stimulate production of VLDL cholesterol.
Cholesterol/HDL ratio – over 4.5 is associated with higher incidence of heart disease.
CRP – C-reactive protein – relates to the degree of inflammation in the system. Higher levels are associated not only with higher inflammatory state, but also with higher risk of heart disease.
Homocysteine – has been used as a measure of heart disease risk. It is a step on the metabolic way from methionine to cysteine (which is a component of glutathione) and probably more accurately reflects the ability of the body to produce and utilize methyl groups used in detoxification.
Sedimentation rate – sed rate – is another marker of inflammation in the body – higher numbers mean higher inflammatory state.
TSH – thyroid stimulating hormone – is secreted by the pituitary gland in the brain, in response to a low level of thyroid hormone (T4) in the blood stream.
Thyroid hormone synthesis is dependent upon multiple factors, including amino acids (phenylalanine and tyrosine in particular), minerals (selenium, iodine, and zinc), and blood levels of fatty acids.
T4 – tetraiodothyronine – this form of iodine is produced in the thyroid gland, and serves as the negative feedback to stop TSH and therefore its own synthesis. Synthroid® is the best known form of T4 hormone. Total T4 measures all the T4 in the blood, whether it is useful or bound to proteins and unavailable to the body. Free T4 measures the amount of T4 which is available for conversion to T3.
T3 – triiodothyronine – this is the active form a thyroid hormone used in the body. It is made by removing an iodine molecule from T4. Cytomel® is the best known form of T3 hormone. Total T3 measures all the T3 in the blood, whether it is useful or bound to proteins and unavailable to the body. Free T3 measures that amount of T3 which the body can actually use.
TPO antibody – measures the activity against thyroid peroxidase, which is important in the conversion of T4 to T3. There is an association between thyroid autoimmunity and breast cancer, possibly related to inhibition of uptake of iodine in the ducts of the breasts as well as in the thyroid gland.
Thyroglobulin antibody – measures the activity against thyroglobulin, or thyroid hormone. People with poorly functioning thyroids often have antibodies to their own thyroid tissue or hormones – this is called autoimmune thyroiditis.
Reverse T3 – is an inactive form of thyroid hormone.