BIOCHEMISTRY I

Lesson 2

Automation in Clinical Chemistry

Part II

Introduction to Clinical Chemistry

Blood chemistry test: routine or scheduled

Routine - frequently ordered (e.g. glucose test,

chemistry profiles such as renal, lipid and liver

profile).profile).

Scheduled - performed only 2 or 3 times / week

(e.g. hormone, certain drugs levels). These tests

are requested when a particular diagnosis is

suspected or treatment must be monitored.

Types of Specimen for Chemical Analysis

Specimens include:

Blood

Urine

Cerebrospinal fluid Cerebrospinal fluid

Synovial fluid

Pleural fluid

Ascites fluid

Pericardial fluids

Less common,

collected by

physician only

Units of Measurement

Usually reported in metric units or SI units.

Commonly used:

Milligrams (mg) or micrograms (g) per

deciliter (dL).deciliter (dL).

Millimoles per liter (mmol/L)

Enzymes activity units per liter (U/L)

Analytes Commonly Tested in Chemistry

Profile

1. Protein

Essential components of cells and body fluids

2 major groups of serum protein: albumins and globulinsand globulins

Albumins: made in liver, serve as transport proteins and help maintain fluid balance in body (by maintaining colloid osmotic pressure).

Globulins: antibodies, blood coagulation proteins, enzymes and proteins that transports irons

Analytes Commonly Tested in

Chemistry Profilea. Total Serum Protein

Normal concentration: 6.0 - 8.0 g/dL (60 - 80 g/L)

Provides information about the state of hydration, nutrition and liver function (as hydration, nutrition and liver function (as most serum proteins are made in the liver).

Proteins are most commonly measured in serum, but can also be found in urine and CSF (concentration is normally low).

Can be measured clinically using a refractometer.

Analytes Commonly Tested in

Chemistry Profile

b. Albumin

Normal concentration: 3.8 - 5.0 g/dL

Hypoalbuminemia (decreased level of Hypoalbuminemia (decreased level of

albumin) cause by liver disease, starvation,

impaired amino acid absorption, increased

protein catabolism and protein loss

through skin, kidneys or gastrointestinal

tract.

Analytes Commonly Tested in

Chemistry Profile

c. Albumin to Globulin Ratio

Total serum protein and albumin are

usually measured in a sample together.

Globulins is computed from the difference

(total protein - albumin = globulin).

Ratio of albumin to globulin (A/G ratio) -

computed and reported.

Analytes Commonly Tested in

Chemistry Profile

2. Electrolytes

Refers to the major ions: cations (Na+ & K+) and

anions (Cl- & HCO3-).anions (Cl & HCO3 ).

All those affect hydration and pH balance, heart

and muscle formation.

Sodium: 135 - 148 mmol/L

Potassium: 3.5 - 5.4 mmol/L

Chloride: 98 - 108 mmol/L

Bicarbonate: 22 - 28 mmol/L

Analytes Commonly Tested in

Chemistry Profile

3. Mineral metabolism

Commonly measured minerals are calcium,

phosphorus (phosphate) and iron.phosphorus (phosphate) and iron.

Calcium: for bone and teeth formation, blood

coagulation.

Phosphorus: development of teeth and bones.

Iron: haemoglobin production.

Analytes Commonly Tested in

Chemistry Profile

a. Calcium

Serum calcium reference range: 8.7 - 10.5 mg/dL.

99% of body calcium is bound in calcium complexes in the skeleton and are not complexes in the skeleton and are not metabolically active.

Calcium assay: measure only unbound Ca2+ ions, which are metabolically active.

Hypercalcemia cause Ca deposition in soft organs (e.g. kidney stones).

Hypocalcemia can be life threatening.

Analytes Commonly Tested in

Chemistry Profile

b. Phosphorus

Normal serum phosphorus: 3.0 - 4.5 mg/dL

Mostly found in the form of inorganic phosphate.

80% is in the bone, the rest in high energy 80% is in the bone, the rest in high energy

compound (e.g. ATP).

Level influenced by calcium and certain

hormones.

Analytes Commonly Tested in

Chemistry Profile

c. Iron

Normal serum iron concentration: 65 - 165 g/dL

Iron is transported by transferrin (serum protein)

in blood. in blood.

Anemia is caused by iron deficiency.

Analytes Commonly Tested in

Chemistry Profile

4. Kidney Function

Kidneys: eliminate waste products, maintains

water and pH balance, produce certain

hormones (from adrenal glands e.g.hormones (from adrenal glands e.g.

aldosterone).

Substances are excreted and reabsorbed from

urine to maintain homeostasis.

Analytes Commonly Tested in

Chemistry Profile

a. Creatinine

Normal serum creatinine: 0.7 - 1.4 mg/dL

Creatinine is the waste product of creatine

phosphate.phosphate.

Their levels are not affected by diet or hormone

levels.

Increases when there is impairment of urine

formation or excretion.

Analytes Commonly Tested in

Chemistry Profile

b. Blood Urea Nitrogen (BUN)

Normal BUN concentration: 8 - 18 mg/dL

BUN is a measure of surplus amino acids.

Concentration influenced by diet, hormones, and Concentration influenced by diet, hormones, and

kidney function. Therefore, it is not a good

indicator of kidney disease as creatinine.

Analytes Commonly Tested in

Chemistry Profile

c. Uric Acid

Normal serum uric acid: 3.5 - 7.5 mg/dL

Formed from breakdown of nucleic acids and is secreted by kidneys.

Has low solubility - tends to precipitate as uric acid crystals (urates).

Use to diagnose and treat gout (precipitation of uric acid in tissues and joints).

Levels can also increase after massive radiation/chemotherapy - due to increased cell destruction

Analytes Commonly Tested in

Chemistry Profile

5. Liver Function

Role of liver:

Carbohydrate metabolism - glycogen and glucose

Produce plasma proteins, transport proteins and Produce plasma proteins, transport proteins and

blood coagulation proteins

Important in lipid metabolism - source of

cholesterol

Storage site for iron, glycogen and vitamins

Destruction of old cells (phagocytosis) and

detoxification

Analytes Commonly Tested in

Chemistry Profile

a. Bilirubin

Total serum bilirubin: 0.1 - 1.2 mg/dL

Bilirubin is waste product from breakdown of

haemoglobin (formed in liver, excreted in bile)haemoglobin (formed in liver, excreted in bile)

In liver, most bilirubin binds to glucuronide and is

excreted into bile (called conjugated or direct

bilirubin)

Non-conjugated bilirubin (indirect bilirubin)

Analytes Commonly Tested in

Chemistry Profile

Total serum bilirubin = direct bilirubin +

indirect bilirubin

Bilirubin assays measures both total and direct

bilirubin

Indirect bilirubin is obtained by subtraction

Bilirubin assay is done to screen for or monitor

gall bladder or liver dysfunction

Since bilirubin levels are normally low, only

high values are significant

Analytes Commonly Tested in

Chemistry Profile

b. Liver enzymes

Enzymes used to assess liver function are:

Alkaline phosphatase (ALP) Alkaline phosphatase (ALP)

Aspartate aminotransferase (AST aka SGOT)

Alanine aminotransferase (ALT aka SGPT)

Gamma glutamyl transferase (GGT)

Lactate dehydrogenase (LDH)

Analytes Commonly Tested in

Chemistry Profile

i. Alkaline phosphatase (ALP)

Also known as AP

Widely distributed in body especially in bone Widely distributed in body especially in bone

and liver ducts

Reference range: 20 - 130 U/L

Analytes Commonly Tested in

Chemistry Profile

ii. Aspartate aminotransferases

Aspartate aminotransferase (AST) or formerly

called serum glutamic oxaloacetic transaminase

(GOT or SGOT)(GOT or SGOT)

Present in tissues such as cardiac, muscle and

liver

Elevated after myocardial infarction (heart

attack) and liver disease

Reference range: 10 - 37 U/L

Analytes Commonly Tested in

Chemistry Profile

iii. Alanine aminotransferases

Alanine aminotransferase (ALT), formerly called

serum glutamic-pyruvic transaminase (GPT or

SGPT)SGPT)

Low levels in cardiac tissue; high in liver tissue

Level usually rise higher than AST in liver disease

Reference range: 3 - 30 U/L

Analytes Commonly Tested in

Chemistry Profile

iv. Gamma glutamyl transferase (GGT)

Found in kidney, pancreas, liver and prostate

tissue

More helpful than AP in determining liver More helpful than AP in determining liver

damage because GGT remains normal in bone

disease

More useful than AST because it remains normal

in muscle disorders

GGT values are used to monitor recovery from

hepatitis

Reference range: 3 - 40 U/L

Analytes Commonly Tested in

Chemistry Profile

v. Lactate dehydrogenase (LDH)

Also called LD

Level increase in blood during liver disease and

after myocardial infarctionafter myocardial infarction

Reference range: 110 - 230 U/L

Analytes Commonly Tested in

Chemistry Profile

6. Cardiac Function

Creatinine kinase (CK), is an enzyme used to

diagnose myocardial infarction

Following myocardial infarction, CK is released Following myocardial infarction, CK is released

from the damaged heart muscle

Serum CK peaks in about 24 hrs; fall back to

normal range within 3 - 4 days

Reference range: 30 - 170 U/L

Analytes Commonly Tested in

Chemistry Profile

7. Lipid Metabolism

a. Cholesterol & Cholesterol fractions

Serum cholesterol concentration tend to increase

with agewith age

Reference: 140 - 250 mg/dL (best to maintain below

200 mg/dL)

LDL (low density lipoprotein)

HDL (high density lipoprotein)

Remove cholesterol from bloodstream and carry it to liver

VLDL (very low density lipoprotein)

Measured

Analytes Commonly Tested in

Chemistry Profile

b. Triglycerides (TG)

Reference range: 10 - 190 mg/dL

Triglycerides are transported in the plasma Triglycerides are transported in the plasma

bound to lipoproteins

Blood to be tested for triglycerides should be

collected when the patient has been fasting for

12 - 14 hrs

Analytes Commonly Tested in

Chemistry Profile

8. Carbohydrate Metabolism

Glucose

Reference range: 70 - 110 mg/dL Reference range: 70 - 110 mg/dL

Carbohydrate metabolism influenced by insulin

produced by pancreas

Also affected by growth hormone, glucagon and

cortisol

Analytes Commonly Tested in

Chemistry Profile

9. Thyroid Function

In blood, more than 99% of thyroid hormones

are bound to serum proteins and are are bound to serum proteins and are

metabolically inactive

2 major hormones: Thyroxine (T4) & Tri-

iodothyronine (T3)

Thyroid profiles include measurements of free or

total T4, free or total T3 and thyroid stimulating

hormone (TSH) levels

Analytes Commonly Tested in

Chemistry Profile

Reference range for TSH: 0.35 - 5.0 IU/L (mIU/L)

Levels may vary according to age

Reference ranges can be different depending on Reference ranges can be different depending on

the assay method

Less Commonly Ordered Clinical

Chemistry Tests

Special tests that measure:

Insulin

Growth hormone

Adenocorticotrophic hormone (ACTH) Adenocorticotrophic hormone (ACTH)

Follicle stimulating hormone (FSH)

Less Commonly Ordered Clinical

Chemistry Tests

Other tests measure:

Vitamins

Trace minerals

Isoenzymes Isoenzymes

Metabolic products

These tests need special specimen collection

and specialised instrumentation

A clinical chemistry test should be consulted

for more information