Interpretation of Laboratory Results

Question 1

Pre-analytical variation examples

Answer 1

Diet=
Dietary constituents can affect analyses e.g triglycerides need 12 hour fast.
Drug such as caffeine and alcohol
Some tests require special diet

Question 2

Pre-analytical variation

Answer 2

Exercise can increase CK and testosterone.
Volume lost through sweating leads to dehydration.

Stress- increases cortisol, glucose and cholesterol
Hyperventilation can cause respiratory alkalosis and increase potassium

Question 3

Pre-analytical variations

Answer 3

Medication=drug interactions

Body position = increase proteins and protein bound constituents

Hydration= dehydration increase concentration of analyses and vise versa

Question 4

Pre-analytical variation

Answer 4

Phlebotomy haemoconcentration if tourniquet (band around arm) left on for too long.
Can increase potassium if clench cost too many times.
Collecting blood near infusion site causes dilution

Question 5

Pre-analytical variation

Answer 5

Haemolysis= red cells have high levels of potassium and LDH
Hb affects method.
Time
Some analyses are unstable in contact with red blood cells
Some need to be refrigerated immediately
Some need to be frozen eg VIP
Many analyses are time dependent eg troponin
Circadian rhythm
Cholesterol increase in winter
Ca2+ higher in summer

Question 6

Pre-analytical variation

Answer 6

Centrifugation= too long or too fast can cause haemolysis

Transport delay may cause affect in some analytes.
Some need to be transported in the dark eg porphyrins

Temperature can affect stability of sample

Question 7

Pre-analytical variation

Answer 7

Patient identification wrong name in tube or wrong blood in tube.

Type of tube = tube contains variety of preservatives such as potassium EDTA

Question 8

Examples of analytical variation

Answer 8

Temperature variations
Operator 
Calibration material 
Pipetting imprecision 
Evaporation 
Carry over 
Reagent deterioration

Question 9

Biological variation examples

Answer 9

Daily, monthly and seasonal rhythms 
Diet 
Hydration 
Exercise 
Stress

Question 10

When are serial results significant?

Answer 10

Comparing more than 2 serial results require less overall change to be significant.

Question 11

How much area is covered by mean +/- 2 standard deviations

Answer 11

95.5%

Question 12

How much area is covered by mean +/- 3 standard deviations

Answer 12

99.7%

Question 13

What factors are taken into account in relation of references ranges?

Answer 13

Age related 
Gender related eg testosterone 
Race related eg creatinine 
Pregnancy eg Alkaline phosphatase 
Post menopause eg iron

Question 14

How are lab test results interpreted appropriately

Answer 14

In association with previous results (serial)
In association with other test
In association with clinical context
Look for results that do not fit clinical picture.