Intro To Biochemical Testing

Question 1

Why request a test

Answer 1

-Diagnosis- in response to patient symptoms, confirm diagnosis, differentiate between many diagnosis
-Screening- phenylketonuria in new borns diabetes, cholesterol
-Prognosis- creatinine in CRF
Monitoring- toxicity, kidney and liver function
-Monitoring- We need to no if the treatment is working; toxicity (liver); kidney and liver function

Question 2

The clinical biochemistry cycle

Answer 2

• Clinical question ->
• Requestion form ->
• Take sample ->
• Transport to lab ->
• Reception at lab ->
• Analysis ->
• Report ->
• Question answered ->

Question 3

Request form

Answer 3

• As complete as possible
• Patients ID
• Test required
• Diagnosis suspected/ clincal symptoms
• Drug therapy

Question 4

Plasma and serum

Answer 4

Plasma- aqueous phase of blood, obtained by removal of blood cells to which an anticoagulant has been added

Serum- aqueous phase of blood that had been allowed to clot

Question 5

Sample

Answer 5

Appropriate tube

Good sampling technique

Appropriate storage

Question 6

What is near patient testing

Answer 6

• Increasing range of tests
• Costs invariably higher than traditional lab
• Maintenance and calibration of instruments

-Used in diabetes- blood glucose

Question 7

What is sensitivity and specificity

Answer 7

• A 100% sensitive test is positive in all patients with the disease- this is better the specificity because the disease in the patient will be recognised and further tests done
• A 100% specific test if negative in all those patient without the disease

-A test is rarely 100% sensitive and specific
Can result in false positive and false negatives

Question 8

Interpretation of test results

Answer 8

-Use reference ranges to interpret results
-Reference ranges are derived from population studies of healthy individuals
-Reference range not normal range
-Abnormal result not necessarily mean presence of disease
-BUT more deviation from reference range the more likely the condition is present
+Exception serum Cr (product of skeletal muscle, if a young man and old women have similar results, old women could be in renal failure)
-Suspect a single high or low result
-There is no such thing as a normal result

Question 9

What can affect test results

Answer 9

Biological variation 
Analytical variation 
Drugs 
Disease process (RA, CRP)

Question 10

Biological variation that effect test results

Answer 10

Gender
Age (alkaline phosphatase- bone turnover will be higher in children)
Race
Diet (lipid profile should be fasting, effect on triglyceride)
Time of day
Posture
Exercise (vigerous exercise this will raise Cr)
Menstrual cycle (Hormonal)
Pregnancy

Question 11

Analytical variation

Answer 11

• Very small variations on repeated testing

- Quality control essential within lab/between labs