Request For Laboratory Investigations

Question 1

clinical biochemistry tests comprise:

Answer 1

over one- third of all hospital laboratory investigations

Question 2

there are over ____ different tests which may be carried out in clinical biochemistry laboratories

they vary from very simple, such as ______ to the highly complex, such as _______

Answer 2

400, Urinalysis, DNA Analysis

Question 3

It has been said that ___% of all medical decisions encompass _______ data

Answer 3

80%, clinical laboratory data

Question 4

laboratory tests are justified only when:

Answer 4

the clinician determines beforehand how the results will assist in diagnosis or management

Question 5

laboratory investigations can be used:

Answer 5

➤ to screen for metabolic diseases

➤ to help make a diagnosis to monitor treatment

➤ to detect complications

➤ for medicolegal reasons

➤ for research after due permission from patients and approval from the local Ethics Committee e.g The UCTH Health Research Ethics Committee

Question 6

types of tests (laboratory tests)

Answer 6

1) static test

2) dynamic test (dynamic function test)

3) suppression test

Question 7

static tests-

Answer 7

are biochemical investigations performed in the resting state as the patient presents clinically e.g. random plasma glucose

Question 8

dynamic test

Answer 8

tests that puts the organ function or system under stress

It is helpful in detecting subtle or mild abnormality in the organ function It could involve administering a

stimulant or suppressant

Question 9

stimulating dynamic function tests involve:

Answer 9

involves the extreme load of a normal metabolite to test the ability of the organ to cope with the excess load

Question 10

examples of stimulating dynamic function tests:

Answer 10

-loading a large amount of ammonium chloride to test the ability of the renal tubules to acidify the urine

-Increase in plasma cortisol concentration after injection of adenocorticotrophic hormone (ACTH) to measure adrenal function

-metyrapone stimulation test to assess the function of the anterior pituitary and adrenal gland

-oral glucose tolerance test to measure the endocrine pancreatic function

Question 11

suppression tests

Answer 11

this is usually hormonal

they test both the integrity of feedback and the response of the target organ

Question 12

suppression tests examples include:

Answer 12

*they include-

I. Dexamethasone suppression test in the diagnosis of Cushing’s syndrome

II. Saline suppression test in the diagnosis of primary aldosteronism

III. Fludrocortisone suppression test in diagnosis of primary aldosteronism

Question 13

all clinical biochemistry laboratories provide facilities for:

Answer 13

‘urgent’ tests

Question 14

an ‘urgent’ test is one in which:

Answer 14

the clinician is likely to take immediate action

Question 15

biochemical measurements vary for 2 reasons

Answer 15

1) analytical variation and

2) biological variation

Question 16

analytical variation are affected by factors such as:

Answer 16

• Precision and Accuracy
• Sensitivity and specificity
• Quality assurance
• Reference ranges

Question 17

precision is the reproducibility of:

Answer 17

an analytical method

Question 18

accuracy defines how close the _________ is to the _________

Answer 18

measured value, actual value

Question 19

sensitivity of an assay is a measure of:

Answer 19

how little of the analyte the method can detect • New methods may offer improved detection limits which may help in the discrimination between normal results and those of diseased patients

Question 20

specificity of an assay relates to:

Answer 20

how good the assay is in discriminating between analyte of interest and potentially interfering substances

Question 21

quality assurance:

Answer 21

laboratory staff monitor performance of assay using quality control samples to give reassurance that the method is performing satisfactorily with patients’ specimen

• these are internal quality control which are analysed everyday or every time an assay is run

• the expected values are known and the results obtained are compared with previous values to monitor performance

Question 22

biochemical test results are usually compared to:

Answer 22

a REFERENCE RANGE considered to represent the normal healthy state

Question 23

nost reference ranges are chosen arbitrarily to include

Answer 23

95% of values found in healthy volunteers

Question 24

hence, __% of the population will have a normal result without the reference range

Answer 24

5%

Question 25

the further a result is from the limits of the range:

Answer 25

the more likely it is to represent pathology.

Question 26

non-pathological biological factors to consider in the interpretation of lab results • they include:

Answer 26

• between-individual differences such as Age, Sex, Ethnic differences
• within-individual differences such as circadian or diurnal rhythms, stress and anxiety, time of meal, season, posture, exercise, infection, medical history, pregnancy, menstrual history, drug hx, etc

Question 27

pertinent questions that will guide interpretation include:

Answer 27

• Is the result the correct one for the patient?
• Does the result fit the clinical finding?
• How does the result compare to the acceptable reference range?
• If its abnormal, is the abnormality of diagnostic significance?
• If its one of a series of results, has there been a change, and if so, is the change significant?

Question 28

What is done in response to a biochemical report rests with the clinical judgement of the doctor

• However, the doctor should remember to:

Answer 28

‘treat the patient rather than the laboratory report’

Question 29

Information about

• the assay performance,
• biological variation, and

clinical judgement are needed for:

Answer 29

a good application of laboratory results