quality assurance

Question 1

what is preanalysis stage ?

Answer 1

all the steps before the sample is analysed

such as ordering and sample collection

Question 2

what is analysis stage ?

Answer 2

lab activity that gives diagnosis results

such as staining, running the sample on an analyser

Question 3

what is post analysis ?

Answer 3

patients reporting and interpretation of the results

Question 4

what are some of the pre analytical errors ?

Answer 4

precollection variables which is patient related :
exercise - increase in AST , CK , lactate
Diet - high after glucose ,
vegeterains - vitB12 and total lipids are low
diurinal variation - cortisol , ACTH , insulin
stress
posture - upright - increase in albumin

specimen collection and labelling

preserving the specimens , and anticoagulants

specimen transport and storage

Question 5

when are specimens rejected ?

Answer 5

clots in anticoagulated specimen 
icterus , hemolysis 
nonfasting specimen 
improper blood collection 
wrong volume collection

Question 6

what are the recommended blood collection order ?

Answer 6

serum tube - nothing

clot tube - sodium citrate

plasma tube - sodium heparin- biochemical reactions

EDTA tube - hematological

glucose tube - sodium fluoride / sodium heaprin

other collection tubes

Question 7

what does the clot tube contain ? and what is it used for ?

Answer 7

sodium citrate 1:9

the clotting mechanism

Question 8

what does the plasma tube contain ?

and what is it used for ?

Answer 8

lithium heparin / sodium heparin (anticoagulants)

plasma biochemical test and rheology measurements

Question 9

what does EDTA tube contain and what is it used for ?

Answer 9

EDTA-K2

clinical haematology

Question 10

what does the glucose tube contain ?

Answer 10

sodium fluoride and potassium oxalate / sodium heaprin

Question 11

in preanalysis how is the specimen stored ?

Answer 11

open tubes are stored in room temp

not in direct sunlight or heating devices because it increases hemolysis and enzyme denaturation

serum/plasma not removed from cells increases gamma glutamate transferase by 27 percent in half an hour
creatine 110 percent increase in plasma and 60 percent in scrum

Question 12

what are the collection techniques for a finger or heel puncture

Answer 12

infants less than 12 months - lateral or medial plantar heel surface

more than 12 months old , children, adults - palmar surface of second third and fourth finger (first and fifth - no)
should not be oedematous or previously punctured

warm the puncture site
cleanse the puncture site
dry
perpendicular to skin and puncture it
wipe away the first drop of blood
gentle pressure , but do not milk the site - hemolysis and excess tissue fluid
collect specimen in suitable container by capillary action
label specimen - with date anytime , and patient information , indicate it was a skin puncture

Question 13

preanalysis techniques for arterial puncture

Answer 13

0.05ml liquid heparin /1ml blood for blood gas analysis

needle pierce the skin at angle 45-60 degrees , slow and deliberate.

after collection compress the puncture site quickly to expel air from the syringe -3 to 5 minutes

mix the specimen to ensure anticoagulation and place it in ice water - minimise leukocyte consumption of oxygen

Question 14

what are the errors in the analytical step ?

Answer 14

introduction and transport to cute or dilution cup
addition of reagent
incubation errors
mixing of sample and reagent

insufficinet analytical specificity and sensitivity
incorrect calibertaion procedure
reagents

Question 15

what are the errors in post analytical stage ?

Answer 15

wrong calculation
reporting wrong results to patient
incorrect interpretation
flags for specimen that require additional analysis with other method

assessment of clinical significance of results
such critical values
referential values
factors influencing reference range

Question 16

what are the factors which influence reference range ?

Answer 16

different lab methods
different tubes
lab are encouraged to perform their own studies of reference ranges usually be testing 120 samples from non diseased individuals
or can use verified referee interval

Question 17

what is critical value ?

Answer 17

lab result which is life threatening

no universe guidelines which assays should have critical values - what the threshold must be , or whether results should be repeated before reporting

Question 18

what is sensitivity ?

Answer 18

the ability of a test to detect disease
expressed as proportion of people with disease in whom the test comes as a positive
90 percent sensitive - test will prove positive to 90 percent of people who have the disease and 10 percent negative who has the disease

Question 19

what is diagnostic accuracy ?

Answer 19

the ability to discern patient from true disease to non disease

Question 20

what is the predictive value of a positive test ?

Answer 20

probability that a positive test

Question 21

what is accuracy ?

Answer 21

how close the results obtained are to the actual true results

Question 22

what is precision ?

Answer 22

repeatability - if the results obtained can be repeatable

Question 23

when he precision is high and the accuracy is low it tends to be what type of error ?

Answer 23

a systemic error - inaccuracy is always in one direction
they cause ll the test results to be either high or low
due to calibration and reagent

Question 24

what is random error ?

Answer 24

where there is poor precision and and low accuracy