Clinical Chemistry: QC, Protein Electrophoresis, and Reference Ranges

Shift

Abrupt change in results over to one side of the mean.

Trend

Gradual decline.

Westgard rules 1 2s

Warning.

Westgard rules 4 1s

Systematic, but does not necessarily mean run is automatically rejected.

Westgard rules 1 3s

Random error.

Westgard rules 10 x

10 data points on one side of the mean indicating systematic error.

Westgard rules 2 2s

Used both within and across runs, indicates systematic error.

Westgard rules R 4s

Random error used ONLY WITHIN runs.

Control

Used to verify the validity of a test or procedure, meant to mimic a potential patient.

Standard

Pure, used to set calibrators, NIST certified composition.

Calibrator

Device used to match the analytical signal with a concentration value of an analyte.

Standard deviation

The average distance from the center of the data (mean) and every value in the data set.

Precision

Dispersion of repeated measurements about the mean due to analytical error.

Accuracy

How close the measured value is to the true value due to systematic error, which can be either constant or proportional.

CV (coefficient of variation)

A method used to compare SDs with different units that reflects the SDs in percentages.

95% confidence

95% of all data points will fall within 2 SD (standard deviation) of the mean.

Gaussian curve

Normal bell curve, shows SD values with mean as the center of 'hill'.

Glucose Fasting plasma

70-100 mg/dL.

Glucose Whole blood

60-85 mg/dL.

Glucose CSF

40-70 mg/dL.

Glucose seizures/coma

At < 30 mg/dL.

Glucose lethargy/neuro effects

At < 50 mg/dL.

Glucose Irritability

At < 60 mg/dL.

OGTT gestational fasting

At < 95 mg/dL.

OGTT gestational 1 hour

At < 180 mg/dL.

OGTT gestational 2 hour

At < 155 mg/dL.

OGTT gestational 3 hour

At < 140 mg/dL.

OGTT normal

At < 140 mg/dL.

OGTT Impaired

140-199 mg/dL.

OGTT Diabetic

>200 mg/dL.

Albumin Plasma

4.0-5.0 g/dL.

Albumin Urine 24 hour collection

Microalbuminuria

30-299 micrograms/milligram creatine.

Clinical albuminuria

Over 300 micrograms/milligram creatine.

Bilirubin Total

0.1-1.2 mg/dL.

Bilirubin Direct

0.05-0.40 mg/dL.

Urea Normal plasma

20 micrograms/dL.

Urea Urine

20 mg/dL.

Total protein Biuret method

Protein reacts with copper ions in solution under alkaline conditions to produce a colored complex.

Albumin method

Albumin binds to bromocresol green to produce a color complex.

Absorbance

The absorbance of said colored complex is proportional to total protein concentration.

Turbid/lipemic specimens

Lipids in sample will falsely increase absorbance readings and give corresponding falsely elevated concentration.

Protein electrophoresis

Basic principle: proteins will separate based on size and electrical charge through a gel medium.

Transthyretin

Normal range - 20-40 mg/dL; 1st peak encountered on electrophoresis results; synthesized in liver; functions: binding and transporting thyroid hormones and retinol binding protein; used in assessing nutritional status of patients.

Albumin

Most common protein in serum; second and largest spike in protein results; if shoulder is present on left side of graph, sample is icteric or lipemic. If on the right side, biliary disease may be suspected as causing increased lipoproteins or pigments; made in liver; normal range: 3.5-5.0 g/dL; functions: maintains osmotic pressure, general transport of bilirubin, metal ions, fatty acids, amino acids, drugs, hormones.

Alpha-1 Acid Glycoprotein (AGP)

Positive acute phase reactant (increases during inflammation) with a reference range of 50-250 mg/dL.

Alpha-1 Antitrypsin

Inhibits proteolytic enzymes, made in liver, with a normal range of 90-200 mg/dL.

Alpha-2 Macroglobulin

Protease inhibitor made by liver, with a normal range of 150-350 mg/dL, not excreted by kidneys.

Haptoglobin

Binds free hemoglobin, prevents renal damage, with a reference range of 30-280 mg/dL.

C3 Complement

Part of Beta-2 fraction, reference range of 90-180 mg/dL, increased in late acute phase reactions.

Gamma Fraction of electrophoresis- Immunoglobulins

Includes IgA- Beta and IgM- between beta and gamma, increased in multiple myeloma and chronic infections.

Anion gap calculation

[(sodium concentration) + (potassium concentration)] - [(chloride concentration) + (bicarbonate concentration)].

Metabolic acidosis

Decrease in basic (HCO3) reactants in renal processing, causes acid buildup.

Respiratory acidosis

Retention/overproduction of CO2 in the blood from hypoventilation.

Metabolic alkalosis

Increased HCO3 in extracellular fluid due to gastric fluid (acid) loss due to vomiting or diuretics.

Respiratory alkalosis

Decrease in CO2 due to hyperventilation.

Carbonic acid relationship to pCO2

H2CO3 is part of the chemical reaction that creates CO2 and can change the pH of blood.

Clark electrode

Electrode specific for oxygen, used to measure PO2.

Osmolality calculation

φnC = osmol/kg H2O, where Φ = osmotic coefficient; n = number of particles; C = molality in moles per kg of H2O.

Electro-osmotic flow

The bulk flow of liquid towards the cathode upon application of an electric field.

Denaturation of proteins

Disturbance of a protein's secondary, tertiary, or quaternary structure, causing loss of function.

Low albumin

Indicates liver disease, protein loss, or malnutrition.

High albumin

Indicates dehydration.

Increased haptoglobin

Occurs in acute inflammatory responses and in renal disease.

Decreased haptoglobin

Occurs in hemolysis, incompatible transfusion reactions, and liver disease.

Increased Alpha-1 Antitrypsin

Occurs in inflammatory conditions, in pregnant patients, and those with tumors.

Decreased Alpha-1 Antitrypsin

Due to genetic deficiency.

Increased Alpha-2 Macroglobulin

Occurs in nephrotic syndrome patients.