Week 2 - QC & QA

Week 2 of Clin Path - Quality Control & Quality Assurance.

What are the 3 phases of quality control?

Pre-analytical

Analytical

Post-analytical

Give examples of pre-analytical steps.

Patient ID

Fasting/diet guidelines

Avoiding stress/meds

Correct blood collection technique.

Give examples of analytical steps

Checking sample quality (no hemolysis/lipemia)

Reagent handling

Instrument maintenance

Running controls

QC charts

Gives examples of post-analytical steps.

Recording results

Recognizing artifacts

Preparing samples for shipping

What is the difference between serum and plasma?

Plasma = fluid with fibrinogen

Serum = Plasma without fibrinogen (after clotting).

What is in a red top tube?

No additives —> serum

What is in an SST (tiger/mottled/cherry)?

Clot activator + gel to separate serum.

What is in a lavender (purple) top tube?

EDTA anticoagulant —> whole blood/plasma, preferred for CBC.

What is in a green top tube?

Heparin anticoagulant —> plasma, common for chemistries.

What is in a gray top tube?

Potassium oxalate + sodium fluoride —> plasma, used for glucose.

What is in a blue top tube?

Sodium citrate —> coagulation studies.

Why is the order of draw important?

Prevents cross-contamination of additives.

What is the correct order of draw?

Blue —> Red —> SST —> Green —> Purple —> Gray

How do impedance analyzers work?

Electric current counts cells by size

What does the Buffy Coat system measure?

Estimates cell counts via differential centrifugation.

How do laser-based analyzers work?

Use lasers to measure cell size & density.

What does total protein tell you?

Hydration status

High TP = dehydration

Low TP = overhydration

How can total protein be measured?

Refractometer or photometry.

What condition can falsely elevate TP?

Lipemia

What is the most important plasma protein?

Albumin (35-50% of total protein)

What causes hypoalbuminemia?

Liver disease

Kidney loss

GI disease

Poor diet

How are globulins estimated?

Total protein - albumin

What is the A/G ratio in dogs, horses, sheep, goats?

Greater than 1

What is the A/G ratio in cattle, pigs and cats?

Less than or equal to 1.

What is fibrinogen’s role?

Precursor of fibrin, 3-6% of TP, only in plasma, acute phase protein.

What are key liver functions?

Metabolism

Protein synthesis

Bile production

Detox storage.

What are signs of liver/gallbladder dysfunction?

Jaundice

Hypoproteinemia

Clotting problems

Hypoglycemia

Hepatic encephalopathy

What are leakage enzymes?

Enzymes released from damaged hepatocytes: ALT, AST SDH (ID), GLDH.

Which leakage enzyme is liver-specific in dogs/cats?

ALT

Which enzyme rises with both liver and muscle damage?

AST

Which enzyme is used in large animals?

SDH (ID)

Which enzyme is high in ruminants and birds?

GLDH

Which enzymes are associated with cholestasis?

ALP (↑ with steroids, bone growth) and GGT (↑ with bile obstruction)

What fraction of bilirubin is prehepatic?

about 2/3.

What do bile acids indicate when elevated?

Liver disease (but not tested if patient is icteric)

How are bile acids tested?

12hr fast —> feed —> test 2hrs post-meal

What does cholesterol measurement show?

Liver synthesis & diet; ↑ with some endocrine diseases.

What is the limitation of dye excretion tests?

Mostly used in research (complex & costly)