clinical lab tests and reference ranges W6

Question 1

things to consider when collecting blood samples?

Answer 1

dietary restrictions? - eg fasting for glucose etc
timing? - diurnal variation, time from last dose, stability
affected by venous stasis?
posture? - eg renin and aldosterone affected

Question 2

meaning of different colours of tubes for blood tests?

Answer 2

white - plain serum (no gel)
brown - plain serum (gel)
orange - lithium heparin (anticoagulant)
red - potassium EDTA (anticoagulant)
green - tri-sodium citrate (anticoagulant)
yellow - sodium fluoride/potassium oxalate (anticoagulant)

Question 3

how is reference range acquired?

Answer 3

identify population that doesn’t have disease
consider factors such as age and sex
reference range as 95% of population (1 in 20 out with reference range)

Question 4

skewed distribution?

Answer 4

one tail on distribution curve is longer than the other

Question 5

why do blood tests and ranges differ throughout the country?

Answer 5

poor precision (how reproducible is a result?)
poor accuracy (how near the true value is the result?)

Question 6

pre-analytical errors in lab testing

Answer 6

failure to choose the correct test on correct patient in correct manner
(most common)

Question 7

analytical errors in lab testing

Answer 7

interference in the test itself

Question 8

post-analytical errors in lab testing

Answer 8

failure to get the interpretation right