Introduction To Clinical Chemistry
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INTRODUCTION TO CLINICAL CHEMISTRY Prepared by: Miss Nada
Clini cal ch em istr y is the measurement of the amount of chemicals in body fluids.
Tests are often performed in groups of individual tests, called panels. The Liver Function Test (LFT) is an example of a panel.
Proper sam ple col lec ti on an d h and ling help ensure that the results are valid. Many different specimens can be used, including whole blood, serum, plasma, urine, faeces,
Difference between Plasma & Serum Bl ood pl asm a is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume. It is composed of mostly water (90% by volume), and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide. Blood plasma is prepared simply by spinning a tube of fresh blood in a centrifuge until the blood cells fall to the bottom of the tube. The blood plasma is then poured or drawn off.
Bl ood se rum is blood plasma without fibrinogen or the
Type of anticoagulant:
The preferred anticoagulant for chemistries is he par in —in interferes with the fewest tests. It functions by inactivating prothrombin, one of the clotting factors, and has a green cap. EDTA usually contains sodium or potassium which inhibits the testing process and/or changes the levels of some reagents.
Hemolysis & Lipemia:
He moly sis is the rupture of red blood cells with the release of hemoglobin and the cellular constituents into the plasma, or liquid portion of whole blood. The release of hemoglobin causes the serum or plasma to appear pale red to cherry red in color.
Hemoly sis ca n in terf ere wit h lab res ul ts due to sev eral proce sses:
Leakage of analytes from lysed erythrocytes may cause a false increase in the amount of analyte measured in serum if the analyte is normally present in a greater amount inside the RBC than in plasma. This can occur when measuring the levels of potassium, creatine kinase (CK), and alanine amino transferase (ALT).
If the analyte is normally present in greater amounts in plasma than in the erythrocytes, the analyte will be diluted by the lysing
Color interference (tinting the serum pink or red) can cause false increases when using a spectrophotometer. Hemoglobin, bilirubin and protein are a few of the analytes affected by hemolysis.
Sometimes erythrocyte constituents can react with analytes, causing a false decrease. This can occur when testing for carbon dioxide, thyroxin and insulin.
Hemolysis can cause increased turbidity when using the
Lipemia:
Lipemia: is the presence of an abnormally high concentration of lipid in the blood. Lipemia is another interference that can adversely affect test results. Hemolysis is enhanced by lipemia,
Lipids present in a specimen scatter light and can cause either an increase or decrease in values, depending upon the analytes being evaluated. Because electrolytes are in the aqueous phase of blood, lipids may dilute their concentration. Lipemia can be minimize d by fasting the patient prior to blood collection, by ultracentrifuging the sample or using polymers to precipitate the lipids out of the sample.
CHEMISTRY SYSTEMS
Dry reag en t st rips require the comparison of a color change on the reagent strip with a color chart. These are most commonly used as quick screening tests, and their accuracy is only low to moderate.
We t an d d ry c hem istr y sys tem s utilize a spectrophotometer to mechanically measure color change and are much more accurate than dry reagent trips. The reagent is the difference between the two systems—most
Spe ctr oph otom ete rs use the Beer-Lambert (or Beer’s) law to measure concentrations. This law states that the amount of light absorbed by a solution varies with the concentration of the colored solute. Light is shown through a specimen in a cuvette and the amount of light transmitted is recorded by a photocell. This is then converted into the amount of substance in the sample.
ଊ
Know your glassware
Clini cal ch em istr y is the measurement of the amount of chemicals in body fluids.
Tests are often performed in groups of individual tests, called panels. The Liver Function Test (LFT) is an example of a panel.
Proper sam ple col lec ti on an d h and ling help ensure that the results are valid. Many different specimens can be used, including whole blood, serum, plasma, urine, faeces,
Difference between Plasma & Serum Bl ood pl asm a is the liquid component of blood, in which the blood cells are suspended. It makes up about 55% of total blood volume. It is composed of mostly water (90% by volume), and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide. Blood plasma is prepared simply by spinning a tube of fresh blood in a centrifuge until the blood cells fall to the bottom of the tube. The blood plasma is then poured or drawn off.
Bl ood se rum is blood plasma without fibrinogen or the
Type of anticoagulant:
The preferred anticoagulant for chemistries is he par in —in interferes with the fewest tests. It functions by inactivating prothrombin, one of the clotting factors, and has a green cap. EDTA usually contains sodium or potassium which inhibits the testing process and/or changes the levels of some reagents.
Hemolysis & Lipemia:
He moly sis is the rupture of red blood cells with the release of hemoglobin and the cellular constituents into the plasma, or liquid portion of whole blood. The release of hemoglobin causes the serum or plasma to appear pale red to cherry red in color.
Hemoly sis ca n in terf ere wit h lab res ul ts due to sev eral proce sses:
Leakage of analytes from lysed erythrocytes may cause a false increase in the amount of analyte measured in serum if the analyte is normally present in a greater amount inside the RBC than in plasma. This can occur when measuring the levels of potassium, creatine kinase (CK), and alanine amino transferase (ALT).
If the analyte is normally present in greater amounts in plasma than in the erythrocytes, the analyte will be diluted by the lysing
Color interference (tinting the serum pink or red) can cause false increases when using a spectrophotometer. Hemoglobin, bilirubin and protein are a few of the analytes affected by hemolysis.
Sometimes erythrocyte constituents can react with analytes, causing a false decrease. This can occur when testing for carbon dioxide, thyroxin and insulin.
Hemolysis can cause increased turbidity when using the
Lipemia:
Lipemia: is the presence of an abnormally high concentration of lipid in the blood. Lipemia is another interference that can adversely affect test results. Hemolysis is enhanced by lipemia,
Lipids present in a specimen scatter light and can cause either an increase or decrease in values, depending upon the analytes being evaluated. Because electrolytes are in the aqueous phase of blood, lipids may dilute their concentration. Lipemia can be minimize d by fasting the patient prior to blood collection, by ultracentrifuging the sample or using polymers to precipitate the lipids out of the sample.
CHEMISTRY SYSTEMS
Dry reag en t st rips require the comparison of a color change on the reagent strip with a color chart. These are most commonly used as quick screening tests, and their accuracy is only low to moderate.
We t an d d ry c hem istr y sys tem s utilize a spectrophotometer to mechanically measure color change and are much more accurate than dry reagent trips. The reagent is the difference between the two systems—most
Spe ctr oph otom ete rs use the Beer-Lambert (or Beer’s) law to measure concentrations. This law states that the amount of light absorbed by a solution varies with the concentration of the colored solute. Light is shown through a specimen in a cuvette and the amount of light transmitted is recorded by a photocell. This is then converted into the amount of substance in the sample.
ଊ
Know your glassware
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