Biochemical Analysis: Specimen Collection and Processing

Flashcards reviewing key concepts in specimen collection and processing for biochemical analysis.

List pre-collection variables that can influence lab determinations.

Diurnal variation, exercise, and diet.

What should patients avoid 24 hours before blood draw?

Changes in diet, alcohol consumption, and strenuous exercise.

Name two systems used for blood collection.

Syringe and evacuated tube system (e.g., Vacutainer).

What does the color-coding of evacuated tube stoppers indicate?

Whether the tube contains a specific anticoagulant or additive, is chemically clean, or contains no additives.

What is obtained after centrifuging blood collected in a plain tube that's allowed to clot?

Serum

What is obtained after centrifuging blood collected in a tube containing anticoagulant?

Plasma

Advantage of using Serum.

It can be used to measure constituents which would be destroyed or compromised by the anticoagulant chemicals.

Disadvantage of using Serum.

The clotting process causes errors in measurements of potassium, magnesium, phosphate, aspartate aminotransferase & lactate dehydrigenase.

Advantage of using Plasma.

Cleaner sample, time saving, higher yield (20%).

Disadvantage of using Plasma.

Anticoagulants can interfere with certain analytical methods or change the concentration of the constituents to be measured.

What is the function of K3EDTA and K2EDTA anticoagulants?

Chelates or binds calcium.

What is the function of Sodium citrate anticoagulant?

Chelates or binds calcium.

What is the function of Heparin anticoagulant?

Inhibits thrombin formation.

What conditions do Royal blue tubes Sodium heparin, Na2EDTA used for?

Plasma/chemistry/toxicology.

What conditions does Gray tube Sodium fluoride and lithium iodoacetate used for?

Plasma/glucose testing.

What causes hemolysis?

RBC destruction.

How does hemolysis affect test results for intracellular chemicals?

Directly increases serum levels.

What can cause hemolysis during blood collection?

Alcohol not dried, difficulty with phlebotomy, pulling plunger too quickly, shaking the tube, small bore needle, air leakage, etc.

What causes an icteric sample?

Increased bilirubin causing a yellow coloration.

What causes a lactescent sample?

Increased lipids causing a milky coloration.

What are three collection requirements for specimens?

Fasting, timed, and iced.

How should additive tubes be mixed?

Gently invert the tube 5 - 10 times (average 8 times)

How it tubes transported?

Tubes are transported with stopper up, promotes clot formation

Maximum time for separating serum from cells.

Two hours

Maximum time for separating plasma specimens.

One hour

What happens to the laboratory results after prolonged contact with cells?

Increase: CK, Lactate, LD , Ammonia
Decrease in glucose, Bicarbonate, Acid phosphatase

Reasons for Specimen Rejection.

Hemolysis/lipemia, clots present in an anticoagulated specimen, nonfasting specimen when test requires fasting, Improper transport conditions, etc.

What is the general rule to storaging plasma samples?

if plasma samples are not analyzed within 5 hours after separation, storage at 2 to 80C for up to 24 hours is acceptable for most analytes.

What are the several kinds of collection for urine specimens?

random, clean catch, timed, 24- hour and catheterized.

When is a clean-catch, midstream specimen is most desirable?

For bacteriologic examinations.

What are lumbar punctures (LPs) are performed by doctors to collect?

Cerebrospinal fluid (CSF).

What does the tube #1 used for CSF analysis?

Goes to chemistry for glucose and protein analysis, or to immunology/serology.

What does the tube #2 used for CSF analysis?

Goes to microbiology for culture and Gram stain.

What does the tube #3 used for CSF analysis?

Goes to hematology for cell counts.