Med lab blog

Test Description: Creatinine is the waste product of creatine phosphate, a compound found in the skeletal muscle tissue. It is excreted entirely by the kidneys. Increased levels of creatinine indicate a slowing of the glomerular filtration rate. The creatinine clearance test consists of two components: a 24-hour urine collection and a blood sample. Conducting both urine and blood testing allows for the comparison of the serum creatinine level with the amount of creatinine excreted in the urine. This is a more sensitive indicator of kidney function than serum creatinine alone. The creatinine clearance normally decreases with aging due to a decline in the glomerular filtration rate. Since “clearance” means the amount of blood cleared of creatinine in 1 minute, a monitoring of the creatinine clearance rate provides valuable information regarding the progression of renal disease. A minimum creatinine clearance of 10 mL/minute is necessary to maintain life without the use of...

Test Description: Creatinine is the waste product of creatine phosphate, a compound found in the skeletal muscle tissue. It is excreted entirely by the kidneys. The creatinine level is affected primarily by renal dysfunction and is thus very useful in evaluating renal function. Increased levels of creatinine indicate a slowing of the glomerular filtration rate. Since creatinine levels normally remain constant, even with aging, this test is particularly useful in evaluating renal dysfunction in which a large number of nephrons have been destroyed. The creatinine level is usually determined in conjunction with the blood urea nitrogen (BUN) in assessing renal function. The normal ratio of BUN to creatinine ranges from 6:1 to 20:1. Testing of the creatinine level in the blood is also used to monitor patients on drugs known to be nephrotoxic, such as aminoglycosides. Normal Values                 Female:    0.6–1.2 mg/dL (5...

Test Description: Creatine kinase (CK) is an enzyme found primarily in the heart and skeletal muscles, and in smaller amounts in the brain. When the total CK level is substantially elevated, it usually indicates injury or stress to one or more of these areas. When a muscle is damaged, CK leaks into the bloodstream. Determining which isoenzyme (specific form of CK) is elevated will help determine which tissue has been damaged. CK can be measured as the total enzyme in the serum, or each of its three isoenzymes may be measured. The isoenzymes include: CK1 (CPK-BB): produced primarily by brain tissue and smooth muscle of the lungs CK2 (CPK-MB): produced primarily by heart tissue CK3 (CPK-MM): produced primarily by skeletal muscle CK, along with asparate aminotransferase (AST) and troponin, is assessed in the case of suspected myocardial infarction. It typically appears in the bloodstream within 3 to 6 hours of the tissue injury, with peak values occurring 18 to 24 hour...

Test Description: C-reactive protein (CRP) is a glycoprotein produced by the liver, which is normally absent from the blood. The presence of acute inflammation with tissue destruction within the body stimulates its production. Therefore, a positive CRP indicates the presence of an inflammatory process. When the acute inflammation is no longer present, the CRP rapidly dissipates from the body. The CRP typically rises within 6 hours of the start of inflammation, allowing the inflammation to be confirmed much sooner than through the use of the erythrocyte sedimentation rate (ESR), which usually increases about a week after inflammation begins. There are two types of CRP which can be measured. The standard CRP is used to assess how active inflammation is in such chronic problems as inflammatory bowel disease, arthritis, and autoimmune diseases; to assess for a new infection such as in appendicitis and postoperative conditions; and to monitor response to treatment of these ...

Test Description:  Proinsulin is converted to insulin in the beta-cells of the pancreas. A by-product of this conversion is C-peptide, an inactive amino acid. C-peptide levels usually correlate with endogenous insulin levels and are not affected by exogenous insulin administration. Measurement of C-peptide levels is useful in: • determining endogenous insulin levels, since the C-peptide level is not affected by exogenous insulin administration; • determining whether hypoglycemia is being caused by nontherapeutic insulin injections (factitious hypoglycemia), in which case the C-peptide level will be low while insulin levels are elevated; • determining presence of an insulinoma, which can be indicated by elevation of both insulin and C-peptide levels; and • monitoring for recurrence of insulinoma, indicated by increasing C-peptide levels. Normal Values                       0.5–2.0 ng/mL (0.17–0.67 nmol/L SI u...

Test Description: In response to a stimulus such as stress, the hypothalamus secretes corticotropinreleasing hormone. This hormone stimulates the secretion of adrenocorticotropic hormone (ACTH) by the anterior pituitary gland. ACTH, in turn, causes the adrenal cortex to release the glucocorticoid hormone, cortisol. Cortisol has several functions, including:           • stimulation of glucose formation (gluconeogenesis)           • stimulation of stored energy molecular breakdown (fats, proteins, carbohydrates)           • promotion of sympathetic responses to stressors           • reduction of inflammation and immune function           • stimulation of gastric acid secretion Most of the cortisol present in the body is bound to cortisol-binding globulin and albumin. Five to ten percent is “free” or unconjugated, and is thus filtered by the kidneys...

Test Description: In response to a stimulus such as stress, the hypothalamus secretes corticotropinreleasing hormone. This hormone stimulates the secretion of adrenocorticotropic hormone (ACTH) by the anterior pituitary gland. ACTH, in turn, causes the adrenal cortex to release the glucocorticoid hormone, cortisol . Cortisol has several functions, including:        • stimulation of glucose formation (gluconeogenesis)        • stimulation of stored energy molecular breakdown (fats, proteins, carbohydrates)        • promotion of sympathetic responses to stressors        • reduction of inflammation and immune function        • stimulation of gastric acid secretion Cortisol levels in the blood provide valuable information regarding the functioning of the adrenal cortex. Cortisol is normally secreted in a diurnal pattern, with the peak or highest levels being between 6 and 8 a...

Test Description Copper is an essential trace element needed in the synthesis of hemoglobin and oxidation reduction. Normally urine contains a very small amount of free copper, since most copper in the plasma is bound to ceruloplasmin, an alpha2-globulin protein. Testing for urine copper content is used to aid in the diagnosis of Wilson’s disease , a hereditary syndrome transmitted as an autosomal recessive trait. In this condition, decreased levels of ceruloplasmin are manufactured by the liver, serum copper levels are low, and urine copper levels are high. Without ceruloplasmin to transport the copper, Wilson’s disease leads to an accumulation of copper in the tissue of the brain, eye, kidney, and liver. One of the hallmarks of this disease is the presence of Kayser-Fleischer rings around the iris of the eye, which are caused by copper deposits. Wilson’s disease can be treated with penicillamine, an anticopper drug, which promotes the renal excretion of excess copper....

Test Description The indirect Coombs’ test is used to detect unexpected circulating antibodies in the patient’s serum which may react against transfused red blood cells. These antibodies are ones other than those of the A, B, and O blood groups. This is different from the direct Coombs’ test, which detects antibodies already attached to the red blood cells. In this test, the patient’s serum is considered the antibody and the donor red blood cells as the antigen. The serum and antigenic red blood cells are brought together to allow any antibodies to attach to the red blood cells. Antihuman globulin is then added. If the patient’s serum contains an antibody that reacted with and attached to the donor red blood cells, agglutination will occur and the test is considered positive. If no agglutination occurs, no antigen-antibody reaction has taken place. The serum may contain an antibody, but the donor red blood cells do not have the antigen against which the antibody would ...

Test Description In some types of diseases, such as infectious mononucleosis and systemic lupus erythematosus, and in sensitizations such as to the Rh factor, the red blood cells become coated with antibodies. The direct Coombs’ test serves as a screening test to determine whether such antibodies are attached to the patient’s red blood cells. In this test a sample of the patient’s blood is mixed with Coombs’ antihuman globulin serum. This serum is actually a rabbit serum which contains antibodies against human globulins. When the patient’s blood is mixed with the rabbit serum, clumping or agglutination occurs if antibodies are present on the patient’s red blood cells. A common cause of a positive direct Coombs’ test is autoimmune hemolytic anemia in which the person has antibodies against his own red blood cells. The test has multiple purposes. It is used to screen blood during type and crossmatch procedures. It can also be used to detect red blood cell sensitization t...

Test Description: The term complement refers to the 20 serum beta-globulin protein enzymes which are a part of the immune system response to antigen-antibody reactions. The complement system is necessary for phagocytosis, destruction of foreign bacteria, and mediation of the overall inflammatory response. Activation of the complement cascade may occur by way of the classic pathway , in which activation is stimulated by an antigen-antibody response, or by the alternate pathway, in which polysaccharides, endotoxins, or immunoglobulins are the stimulating forces. Regardless of the stimulus, the final product of the complement cascade’s work is a complex protein capable of destroying the cell membrane of the antigen. To assess the functioning of the complement system and to determine whether deficiencies of these proteins are contributing to increased infections or increased autoimmune activity, two of the components are typically measured. C3 is involved in both the cl...

Test Description Agglutinins are antibodies which cause red blood cells to aggregate, or clump. These antibodies can cause hemolytic anemia. It is important to know which type of agglutinin is causing the hemolytic anemia so that appropriate therapy can be initiated. Cold agglutinins are active at low temperatures. These antibodies, which are primarily of the IgM type, are most active at temperatures below 37°C, thus the term “cold” is used. This test is often used to diagnose primary atypical pneumonia caused by Mycoplasma pneumoniae. Cold agglutinins usually rise within 8 to 10 days after the onset of atypical pneumonia, peak in 12 to 25 days, and decrease 30 days after onset. Febrile agglutinins are those which are associated with diseases which cause fever. Such infectious diseases include Brucellosis, rickettsial infections such as Rocky Mountain spotted fever and typhus, salmonellosis, and tularemia. To test for febrile agglutinins, a sample of the patient’s ...

Test Description Coenzyme Q10 (CoQ10) is an enzyme essential to mitochondrial ATP generation and antioxidant function in lipid and mitochondrial membranes. According to the American Association of Clinical Endocrinologists (2003), it has been found to have beneficial effects for mitochondrial disorders, congestive heart failure (CHF), and ischemia-reperfusion injury. In cases of insufficient CoQ10, electron transfer activity of the mitochondria decreases. This results in an energy production inadequate for cell operation. This can be especially stressful for tissues with very high energy demand such as the heart muscle. The role of CoQ10 in myopathy associated with statin use is also being studied. Statins have been shown to create a CoQ10 deficiency, especially in the elderly, since the enzyme typically decreases with age and in those with congestive heart failure. The use of CoQ10 supplementation for statin-associated myopathy is starting to gain support, since dietar...

Test Description Whenever there is tissue injury or injury to blood vessels, platelets aggregate at the area of the injury. These platelets release factors which begin the clotting process (hemostasis). The original type of injury dictates the pathway by which the process is initiated. The intrinsic pathway is involved when there is damage to the blood or the blood is exposed to collagen in the walls of traumatized blood vessels. The intrinsic pathway requires the sequential activation of several coagulation factors: factor XII (Hageman factor), factor XI (plasma thromboplastin antecedent), factor IX (Christmas factor), and factor VIII (antihemophilic globulin). The extrinsic pathway is launched when there is injury to tissue or to the vascular wall. In this pathway, clotting is triggered by the release of tissue thromboplastin (factor III) from the damaged vascular or tissue cells. When this substance encounters factor VII (stable factor), the extrinsic pathway is ...

Test Description Clostridium difficile is a gram-positive bacterium that is normally present in the large intestine. When patients are taking broad-spectrum antibiotics, especially ampicillin, cepalosporins, or clindamycin, the normal flora of the intestine are diminished. However, C. difficile is resistant to these antibiotics, so its presence actually increases under these circumstances. Its presence can also increase in immunocompromised patients. C. difficile releases two necrotizing toxins (A and B), one of which causes necrosis of the lining of the colon. This results in the development of Pseudomembranous colitis , a potentially fatal condition, 4 to 10 days after the antibiotic therapy is initiated. Symptoms include complaints of abdominal cramping, fever, and copious amounts of watery diarrhea. Leukocytosis is also present. Through testing for this bacterial infection, treatment can be initiated, including discontinuance of the broad-spectrum antibiotics, a...

Test Description Chromosome analysis involves the study of an individual’s chromosomal makeup, or karyotype. Both chromosomal number and structure are studied. The test is used to determine chromosomal abnormalities and to identify the child’s sex in the case of ambiguous genitalia or prior to delivery. This test is considered part of the workup done for amenorrhea, infertility, and frequent miscarriages. It is also used in genetic counseling for individuals with a family history of genetic disease. Chromosome analysis usually involves a culture of leukocytes from peripheral blood. However, karyotyping may also be completed on other tissues, including amniotic fluid, bone marrow, buccal smear, chorionic villus, placental tissue, skin, and tumor cells. ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ Normal Values                      Female: 44 autosomes, plus 2 X chromosomes; Karyotype: 46,...

Test Description There are two enzymes which hydrolyze acetylcholine (ACh): acetylcholinesterase, or true cholinesterase, and pseudocholinesterase, or serum cholinesterase. Acetylcholinesterase , which is present in nerve tissue, the spleen, and the gray matter of the brain, helps with the transmission of impulses across nerve endings to muscle fibers. Pseudocholinesterase , produced mainly in the liver, appears in small amounts in the pancreas, intestine, heart, and white matter of the brain. Two groups of anticholinesterase chemicals, organophosphates and muscle relaxants, either affect or are affected by these enzymes. Organophosphates, which inactivate acetylcholinesterase, are found in many insecticides and nerve gas. Muscle relaxants, such as succinylcholine, are normally destroyed by pseudocholinesterase. If, however, there is a lack of pseudocholinesterase , the patient may experience a prolonged period of apnea if given muscle relaxants during surgery. Thus...