The Clinical Applications of Pathology Tests and Quality Assurance

Question 1

Where can the cost of various pathology tests be found?

Answer 1

Medicare Benefits Schedule Book

Question 2

What is the Ulysses syndrome?

Answer 2

When a healthy patient receives a false positive result and has many other unnecessary follow-up investigations

Question 3

What are the 4 reasons for pathology tests?

Answer 3

Screening
Diagnosis
Prognosis
Monitoring

Question 4

What should be done if a patient’s test result is above the population median?

Answer 4

If mildly elevated, monitor with another test in some years’ time
If highly elevated, requires action

Question 5

What would be the PPV of a test with 99% specificity and 99% sensitivity where the prevalence of disease is only 1%? What is the clinical implication of this for screening programs?

Answer 5

50% - there would be as many TPs as FPs

In screening programs there are almost always more FPs than TPs

Question 6

What are the FPG, OGTT and HbA1c thresholds for the diagnosis of diabetes?

Answer 6

FPG >7.0 mmol/L
OGTT >11.1 mmol/L
HbA1c >6.5%

Question 7

Describe the Rotterdam criteria for diagnosis of PCOS and how can these findings be elicited clinically

Answer 7

2 or more of the following:
Chronic anovulation (amenorrhoea)
Hyperandrogenism (hirsutism/biochemistry)
Polycystic ovaries (US)

Question 8

For what disease is the Gleason score used to provide an indication of prognosis?

Answer 8

Prostate cancer

Question 9

What is serum sodium used as an indicator for?

Answer 9

Risk factor for in-hospital mortality (increased risk if low or high)

Question 10

Explain the concept of “reversion to the mean” in monitoring

Answer 10

A healthy person oscillates about their set point - this is a good indicator

Question 11

What is the role of tumour marker doubling time in monitoring cancer patients?

Answer 11

Provides an indication of expected exponential growth of tumours

Question 12

What factors are important in therapeutic drug monitoring?

Answer 12

Absorption
Distribution
Drug half life
Peak level, trough level

Question 13

What is important when measuring electrolytes besides the absolute level?

Answer 13

Rate of change

Overall trend

Question 14

How should the y axis units be expressed when monitoring tumour markers?

Answer 14

On a logarithmic scale

Question 15

What % of clinical decisions are based on results from the laboratory?

Answer 15

70-85%

Question 16

What % of laboratory test errors occur at the preanalytical test stage?

Answer 16

68%

Question 17

Give 5 examples of preanalytical error

Answer 17

Insufficient sample
Poor sample condition
Incorrect sample
Incorrect identification
Sample handling and transport

Question 18

KIMMS

Answer 18

Key Incident Management Monitoring System

Question 19

Where do most of these preanalytical errors occur?

Answer 19

Emergency

Question 20

What details should be included on a pathology request slip?

Answer 20

At least 2 patient identifiers
Urgency
Dr name and contact
Collection details and collector
Clinical indication
Signature and date

Question 21

What details should be included when labelling a sample?

Answer 21

At least 2 patient identifiers
Day and time of collection
Collector
NB Should all match up with request slip!

Question 22

What types of tubes are used to prevent coagulation of a blood or plasma sample (e.g. for an FBE, to measure clotting factors)?

Answer 22

K2EDTA (for FBE)
EDTA
Citrate
Oxalate
Heparin

Question 23

What sample is allowed to clot? Why?

Answer 23

Serum

To get rid of clotting factors which can interfere with tests, e.g. immunoassays

Question 24

When is acid preservative added to a urine sample?

Answer 24

When measuring calcium and/or catecholamines

Question 25

When is alkaline preservative added to a urine sample?

Answer 25

When measuring uric acid

Question 26

When should a urine sample be refrigerated?

Answer 26

For MCS

Question 27

When should a spot faecal sample taken?

Answer 27

FOBT

Question 28

When should a 3 day faeces collection be taken?

Answer 28

For faecal fat

Question 29

Why are 3 samples taken during lumbar puncture?

Answer 29

Because often some initial blood contamination; first tube for chemistry, second culture, third microscopy (where it is important to analyse for RBCs in the CSF)

Question 30

List 5 common errors in blood collection

Answer 30

Haemolysed specimen
Delayed transport
Inappropriate refrigeration
Contamination from another tube type
Drip arm specimen

Question 31

What effect does haemolysis have on potassium levels?

Answer 31

Artificially elevates

Question 32

How long does it take for a RBC sample take to consume its glucose?

Answer 32

3 hours; after this will haemolyse

Question 33

What is the effect of refrigeration on a RBC sample?

Answer 33

Cells stop working within 30 mins

Question 34

How is a ruptured specimen produced?

Answer 34

Via turbulent collection of samples through fine bore needles/taps

Question 35

What is the “order of draw” for collection of blood samples?

Answer 35

From non-preservative containing tubes to tubes with preservatives

Question 36

What is the major issue with contamination from an FBE tube?

Answer 36

Will cause artificially high K+ and low Ca2+; this is normally a medical emergency

Question 37

If there is a drip in the wrist, what % of cubital vein blood on the same arm will be drip?

Answer 37

30%

Question 38

What can be used to prevent glycolysis (in order of quickest to slowest effect)?

Answer 38

Acidity (i.e. fluoride citrate)
Serum gel tube if spun
Fluoride