Clinical I NSG 522 – Laboratory Tests Performed on Blood and Body Fluids
Overview
Blood chemistry tests measure the amounts of chemical substances in blood. Routine blood chemistry tests help evaluate function of major organs and indicate a person’s overall state of health. They are usually prescribed as a panel, a group of tests that can be done at one time. Tests included in a panel as well as the names of panels can differ from laboratory to laboratory. Reference ranges of expected values for tests can also differ because of the way a test is done in a specific laboratory.
Common blood chemistry tests include:
Electrolyte studies
Plasma glucose
Hemoglobin A1c
Lipid profile
Liver function tests
Kidney function tests
Cardiac markers
Electrolyte Panel
An electrolyte panel (also referred to as
electrolytes
,
serum electrolytes,
or
“lytes”
) measures the four main electrolytes found in the blood:
Sodium (Na
+
)
Potassium (K
+
)
Chloride (Cl
–
)
Bicarbonate (HCO
3
–
) or total carbon dioxide (CO
2
)
The panel is performed on a sample of venous blood.
Reasons for Prescribing
An electrolyte panel is done to identify:
Fluid imbalance
Abnormal numbers of electrolytes
Abnormalities in acid-base balance
Expected Value Range
Na
+
136–145 mEq/L
K
+
3.5–5 mEq/L
Cl
–
98–106 mEq/L
CO
2
23–30 mEq/L
Interpretation of Abnormal Values
Abnormal values are often due to dehydration from excessive heat, vomiting, or diarrhea.
Plasma Glucose
Plasma glucose (blood sugar) is a measure of the amount of glucose circulating in the blood. A plasma glucose test is done in the laboratory on a sample of venous blood or at the point of care on a sample of capillary blood. It may be a fasting test (no food or drink, except water, usually for 8 to 12 hours) or a nonfasting test.
Reasons for Prescribing
Plasma glucose, or blood sugar, is measured to:
Detect abnormal glucose metabolism
Monitor effectiveness of treatment regimens for diabetes and other disorders of glucose metabolism
Expected Value Range
Plasma glucose: 74 to 106 mg/dL
Interpretation of Abnormal Values
Values are elevated with obesity and in diabetes mellitus.
Values are decreased with malabsorption, too much insulin, anxiety, and excessive exercise.
Hemoglobin A1c
Hemoglobin A1c (HbA1c, A1c test, glycosylated hemoglobin) is a measure of average plasma glucose level over 60 to 90 days. It is done on a sample of venous blood, no fasting required.
Reasons for Prescribing
HbA1c is done to:
Diagnose prediabetes, type 1 diabetes, and type 2 diabetes
Monitor effectiveness of diabetes treatment plans
Expected Value Range
People without diabetes: HbA1c 4% to 5.9%
People with diabetes: HbA1c ≥6.5%
Interpretation of Abnormal Values
People with diabetes that has been well controlled over the past 2 to 3 months have values below 7%. If diabetes is poorly controlled, values are 9% or higher.
Lipid Profile (Lipid Panel)
A lipid profile is a measure of four fats circulating in the blood:
Total cholesterol
Low-density lipoprotein (LDL) cholesterol
High-density lipoprotein (HDL) cholesterol
Triglycerides
It is performed on a fasting (no food or drink, except water, usually for 8 to 12 hours) sample of venous blood.
Reasons for Prescribing
A lipid profile is done to detect hyperlipidemia and to estimate risk for atherosclerotic heart and blood vessel disease.
Expected Value Range
Interpretation of Abnormal Values
Cholesterol
<200 mg/dL Elevated with obesity and atherosclerosis Low-Density Lipoproteins <130 mg/dL Elevated with a high-cholesterol diet and diabetes mellitus High-Density Lipoproteins Males: >45 mg/dL
Females: >55 mg/dL
Decreased with obesity, smoking, stress, and chronic inactivity
Triglycerides
Males: 40–160 mg/dL
Females: 35–135 mg/dL
Increased with alcohol abuse
Liver Profile
A liver profile is a set of liver function tests that typically include serum levels of:
Albumin
Bilirubin
Four liver enzymes:
Alanine aminotransferase (ALT)
Alkaline phosphatase (ALP)
Aspartate aminotransferase (AST)
Gamma-glutamyl transpeptidase (GGTP)
A liver profile is performed on a sample of venous blood.
Reasons for Prescribing
To screen for or monitor liver disease
Levels of albumin and bilirubin indicate how well the liver is making protein and clearing bilirubin, which is a waste product. The enzyme levels are measures of liver disease because the enzymes are released from damaged liver cells. Clinical I NSG 522 – Laboratory Tests Performed on Blood and Body Fluids
Expected Value Range
Albumin
3.5–5 g/dL
Bilirubin (total)
0.3–1.0 mg/dL
Alanine Aminotransferase (ALT)
4–36 units/L
Alkaline Phosphatase (ALP)
30–120 units/L
Aspartate Aminotransferase (AST)
0–35 units/L
Gamma-Glutamyl Transpeptidase (GGTP)
Males and females >45 yr: 8–38 units/L; females <45 yr: 5–27 units/L Interpretation of Abnormal Values All values, except albumin, are elevated in liver disease. Albumin is decreased. Renal Function Studies Renal function studies consist of two basic measurements: Blood urea nitrogen (BUN) Serum creatinine As a measure of renal function, the BUN is interpreted in conjunction with the serum creatinine. Renal function studies are performed on samples of venous blood. Reasons for Prescribing To monitor renal function and to assess kidney damage Expected Value Range Blood Urea Nitrogen (BUN) 10–20 mg/dL Creatinine Males: 0.6–1.2 mg/dL Females: 0.5–1.1 mg/dL Interpretation of Abnormal Values Both BUN and creatinine are elevated in acute and chronic kidney disease. Cardiac Markers Cardiac markers are proteins that are released from injured heart muscle cells into the bloodstream. Cardiac markers include: Creatine kinase (CK) and the CK-MB isoenzyme Myoglobin Troponin I Troponin T Cardiac markers are measured on a sample of venous blood. Reason for Prescribing To detect damage to the myocardium from occlusion of the coronary arteries Expected Value Range/Abnormal Values Blood levels of cardiac markers change in a predictable manner over time after damage to cardiac muscle. Marker Expected Values Abnormal Values Begins to Rise (h) Peak (h) Returns to Normal (days) Total creatine kinase Females: 30–135 units/L Males: 55–170 units/L Females: >150 units/L
Males: >174 units/L
6
18
2–3
CK-MB
<0% >3%
4
18
2
Myoglobin
<90 ng/mL >90 ng/mL
3
8–12
Within 1
Troponin I
<0.03 ng/mL >0.04 ng/mL
4–6
10–24
4
Troponin T
<0.1 ng/mL >0.1 ng/mL
4–6
10–24
10
Clinical I NSG 522 – Laboratory Tests Performed on Blood and Body Fluids
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