Clinical Chemistries: Intro to Clin Chem Flashcards
What do Clinical Chemistries allow us to do?
Measure chemical components in the body that gives us information about the function of different organs
What type of sample do most chemical analyses require?
Serum
How long after collection do you need to analyze the sample?
1 hour
What should you do with the sample if you cannot analyze it within one hour?
Separate it and then refrigerate or freeze the sample
Good sample collection
Collect blood samples before treatment
The patient should be fasted
Use the largest vein possible
Use the proper syringe and needle size
Serum
Fluid portion of clotted blood
No fibrinogen
SST or RTT
Plasma
Fluid portion of whole blood
Has fibrinogen
GTT (heparin) or BTT
What is the advantage for using a green top tube?
You do not need to wait for the blood to clot before spinning for emergency/stat tests
What is the disadvantage for using a green top tube?
Only works as an anticoagulant for 8-12 hours
Can not use to send to lab
What happens to the serum during the clotting process?
The soluble fibrinogen in plasma is converted to an insoluble fibrin clot matrix
What happens to clotted blood when it is centrifuged?
The fluid is squeezed out and becomes serum
What happens when you centrifuge higher than 2000-3000 rpm for prolonged times?
Hemolysis may result
What is inside a serum separator tube?
Gel that forms a barrier between serum and blood cells
What do the inside walls of the serum separator have?
Silica particles that aid in clot activation
What do you do with the serum separator tube after blood has been collected?
Invert gently and let it sit for 20 minutes
Red top tube
No additives
Allow the clot to form by letting the blood sit for 20 minutes
At what speed do you centrifuge the red top tube at and for how long
10 minutes
2000-3000 rpm
What do you do with the serum after it is centrifuged?
Remove it with a pipette
Transfer it to another red top tube or white top tube
What can falsely affect chemistry results?
Chemical contamination
Improper labeling and handling
Lipemia
Sample is left on the clot for too long before it was removed
What causes hemolysis?
A damp syringe from auto-claving
Trauma to the RBCs
Sample is frozen or overheated
Too much alcohol on the skin
How does hemolysis affect the sample?
It alters the makeup of serum or plasma
How does hemolysis alter the makeup of serum or plasma?
The fluid from ruptured cells can dilute the sample
Can elevate potassium, phosphorus and enzymes
Can alter lipase and bilirubin values
What fives things can you do to prevent hemolysis?
Mix the sample gently
Remove the needle from the syringe and transfer the blood directly into the tube
Good venipuncture technique with minimal trauma
Use large veins when possible
Never freeze whole blood
What seven factors can influence the results of the clinical chemistries?
Chemical contamination (rare) Improper labeling Improper sample handling Icterus Fasting collections Collecting immediately after a meal Lipemia
How can improper labeling influence results?
Serious errors may occur
Wrong results for the patient
complete the request form correctly
How can improper sample handling influence results?
Analyze within one hour
Keep at room temperature or freeze if over one hour
Heat can destroy come chemicals and activate others
What happens if serum is left on the clot for too long
False decrease in glucose at a rate of 10% per hour by RBCs in vitro
False change in electrolytes (phosphorus and potassium) and some liver enzymes (ALT, AST)
How can collecting blood immediately after a meal influence results?
The blood glucose will be elevated
Inorganic phosphorus will be decreased
Lipemia
Kidney assay affected
How can Lipemia influence results?
High fat content in blood
Milky appearance to serum
Can cause errors with various chemistry tests
How long should a patient be fasted prior to sample collection?
8-12 hours
What are some causes of inaccurate results?
Poor-quality or outdated reagents Failure to calibrate or run controls Improper pipetting techniques Improper maintenance of instruments Lipemic or hemolyzed samples Allowing the serum to sit on the clot Improperly trained employees
What are the three types of errors?
Clerical
Random
Systematic
Clerical Errors
Mistakes in recording of data. sampling wrong patient, incorrect math calculations
Random Errors
Variations found in the lab including equipment failure, timing error
Systematic errors
Inaccurate standard control samples, reagent instability, handling errors, wrong method for a particular sample
