Introduction to Clinical Chemistry Flashcards
homeostasis
the tendency toward steady state or equilibrium of body processes
analyte
a chemical substance that is the subject of chemical analysis
preanalytical phase
the collection, handling and storing correctly until tests are performed
analytical phase
using correct procedures and appropriate quality assessment measures to analyze specimens
AKA quality control
postanalytical phase
reporting accurate and calculated test results
routine chemistry tests
AKA complete metabolic profile, is a group of tests performed simultaneously on a patient specimen to provide an assessment of the patient’s general condition.
ie. state of carbohydrate and lipid metabolism, liver and kidney tests
Special chemistry tests
tests that are ordered less frequently
ie. hormones or certain drug levels
Chemistry profiles or panels
- reflect general state of health
- evaluate particular organ systems
Specimens used for chemical analysis
blood and urine
Reference range
- determined by measuring the level of the substance in a portion of the general population and applying statistical methods to the data.
ie. when establishing reference range for total protein, a lab might test 100 random samples from the population and calculate the mean value and the standard deviation of the set of values. - the reference range is then determine by adding +-2
ie. the mean is 7g/dL therefore the reference range is 6-8 g/dL
NOTE: * reference value(s) can differ from recommended values
factors affecting reference range
- differ slightly according to the population sample’s geographical area and age of population.
- reference range for a substance measured in plasma vs. serum
- types of analyzers used, testing methods
Note*: each lab must supply its reference range when a test result is reported
reference range for Total Protein
60-80 g/L
albumins(60%) + globulins (40%)
Albumins
-the most abundant protein in normal plasma (60%); a homogeneous group of plasma proteins that are made in the liver and help maintain osmotic balance
Reference range for albumins 38-50g/L
hypoalbuminemia
low level of albumin
Globulins
a heterogeneous group of serum proteins with varied functions, 40% of total protein in serum
(total protein-albumin = globulin)
electrolytes
the cations and anions important in maintaining fluid and acid-base balance
Cation-a positively charged ion
Sodium, Na+ (135-148 mmol/L)
potassium, K+ (3.8-5.5 mmol/L
Anion- a negatively charged ion
Chloride, Cl- (98-108 mmol/L)
Bicarbonate HCO3- (2-28 mmol/L)
Note*- inform provider if sodium result is outside of reference range bc it is related to the relaxation and contraction of the muscle
Mineral metabolism
- Calcium, Ca (1.15-1.33 mmol/L)
- phosphorus (0.96-1.44 mmol/L)
- Iron (11.6-29.5 mmol/L)
hypercalcemia
blood calcium levels above normal
1.15-1.33 mmol/L
hypocalcemia
blood levels below normal
1.15-1.33 mmol/L
Kidney Function
-Creatinine (62-125 mmol/L)
-Blood Urea Nitrogen, BUN (2.9-6.4 mmol/L)
-Glomerular filtration rate, GFR
-Uric Acid (0.21-0.44 mmol/L)
Note*- elevated uric acid causes Gout
Glomerular filtration rate
an estimation of how much blood passes through the glomeruli per unit of time (minute); an estimate of the number of functioning nephrons made by using the rate at which molecules such as creatinine and urea are filtered by the kidneys
Gout
a painful condition in which blood uric acid is elevated and urates precipitate in joints
Liver Function
Bilibrubin- a product formed in the liver from the breakdown of hemoglobin
(2.0-21.0 umol/L)
Enzymes
- Alkaline phosphatase (ALP) (20-130 U/L)
- Aminotransferases (ALT 3-30 I/L) (AST 10-37 U/L)
- Gamma glutamyltransferase (GGT 3-40 U/L)
- Lactate dehydrogenase (LDH 110-230 U/L)
*note- enzymes in the blood are unstable
Alkaline phosphatase(ALP)
20-130 U/L - an enzyme widely distributed in the body, especially in the liver and bone
note liver and bone
Aminotransferases
(ALT 3-30 U/L) (AST 10-37 U/L)
Alanine aminotransferase (ALT)
an enzyme presents in high concentration in the liver and measured to assess liver function; formerly called SGPT
(3-30 U/L)
aspartate aminotransferase (AST)
an enzyme presents in many tissues, including cardiac, muscle and liver and measured to assess liver function; formerly called SGOT
(10-37 U/L)
note* also used to assess heart
difference between ALT and AST
ALT is measured to assess liver function, and AST is measured to assess liver function and heart
Cardiac Markers
Creatine kinase (CK-MB) troponins B-type natriuretic peptide (BNP) C-reactive protein (CRP) Homocysteine
Creatine Kinase (CK-MB)
an enzyme presents in large amounts in brain tissue, heart and skeletal muscle and a form of which is measured to aid in diagnosing heart attach within 24 hour
Total CK 30-170 U/L
Troponins
intracellular proteins that are present in skeletal and heart muscle and are released when muscle is injured
B-Type natriuretic peptide (BNP)
a peptide hormone released primarily from the ventricles of the heart and used as a marker for cardiac function
note*- released from the ventricles of the heart
What is the similarity between skeletal muscle and heart muscle?
they are striated
If a patient is walking with chest pain, what can we measure to see if there is a heart problem?
troponins
homocysteine
an amino acid, elevated blood levels of which are associated with increased risk for vascular and cardiovascular disease
Lipids
any one of a group of fats or fat-like substances
Lipid metabolism
- Total Cholesterol (3.6 -6.5 mmol/L) and fractions LDL, HDL, VLDL
- Triglycerides (0.11-2.15 mmol/L
- hyperlipidemia
Triglycerides
the major storage form of lipids; lipid molecules formed from glycerol and fatty acids. fasting for 12-14 hr
(0.11-2.15 mmol/L)
hyperlipidemia
excessive amount of fat in the blood plasma is milky appearance
Carbohydrate metabolism
glucose (3.9 -6.2 mmol/L)
Glucose metabolism is largely regulated by insulin, which is produced by the pancreas.
Also influenced by glucagon, growth hormone, and cortisol
Thyroid Function
-Thyroid-stimulating Hormone (TSH)
(0.35-5.0 mIU/L
-Thyroxine (T4)
Triiodothyronine (T3)
Other Tests:
Insulin
growth hormone
adrenocorticotropic hormone (ACTH)
Thyroid stimulating Hormone (TSH)
a hormone that is synthesized by the anterior pituitary gland and regulates the activity of the thyroid gland (0.35-5.0 mIU/L)
hyperthyroidism
excessive functional activity of the thyroid gland; excessive secretion of thyroid hormones Grave’s disease
hypothyroidism
underactive function of the thyroid gland; abnormally low production of thyroid hormones
What are the most common specimens used to analyze chemical chemistry?
blood (serum) and urine
how long do we wait before centrifuge SST? Why?
30 MINUTES to let clotting activator mix well and to avoid the buildup of membrane layer
note*- the automated machine will not collect serum if membrane layer detected
Why do we perform the glucose test when checking kidney performance?
Elevated sugar levels signal a variety of metabolic and structural changes in the nephrons preventing them from functioning properly
Will we use whole blood sample in clinical chemistry department?
yes, we use whole blood in the lavender tube for the HBA1C test
Problems in specimen collection and processing
- hemolysis (elevate LD, AST, K)
- hemoconcentration
- over centrifugation
- evaporation
- microbial contamination
- anticoagulant contamination
