CSIM 2.4 Diagnositics 2: Lab medicine

Question 1

Analytical Specificity

Answer 1

High specificity = measures analyte of interest only

Question 2

Analytical Sensitivity

Answer 2

High sensitivity = capable of measuring at lower concentrations

Question 3

Limit of detection (LoD)

Answer 3

Smallest concentration that can be distinguished from zero

Question 4

Limit of quantification (LoQ)

Answer 4

Smallest concentration that can be measured with acceptable precision (e.g. CV = 20%)

Question 5

Analytical Precision

Answer 5

Repeatability of a measurement

Question 6

Accuracy (bias)

Answer 6

How close results are to actual amount present

Question 7

Spectrophotometry

Answer 7

Light absorption measured based on reaction
Urea, creatinine, ALT, ALP, albumin, total protein, calcium, magnesium, CK, urate, LDH, bilirubin, cholesterol, triglycerides, glucose

Question 8

Spectrophotometry Advantages

Answer 8

Quick, cheap, automatable

Question 9

Spectrophotometry Disadvantages

Answer 9

Interference from Haemolysis, lipaemia, icterus, chemical methods not available for many analytes

Question 10

monoclonal antibodies

Answer 10

high specificity, high cost

Question 11

Epitope

Answer 11

Binding regions on an antigen

Question 12

polyclonal antibodies

Answer 12

High affinity, low cost

Question 13

Immunoassay- sandwich type

Answer 13

two antibodies, sandwich the analyte patient sample one has a signal label and this detects the amount of analyte

Question 14

Immunoassay-competitive format

Answer 14

signal analyte bound to capture antibody. Patient sample analyte competes for antibody binding, after incubation signal measured inversely proportional to amount of patient analyte present

Question 15

Immunoassays- examples

Answer 15

Troponin T, BNP, cortisol, testosterone, TFTs, PTH, PSA, CA-125, therapeutic drugs, drugs of abuse screens, B12, folate, serology

Question 16

Immunoassay advantages

Answer 16

Automatable often, quick, wide range of analytes, high sensitivity

Question 17

Immunoassays disadvantages

Answer 17

Cross reactivity (AB binds to other epitopes), can be expensive, if manual slow, heterophilic antibodies (other antibodies bind to immunoassay)

Question 18

Immunohistochemistry

Answer 18

Identification of specific molecules in tissue samples via labelled antibodies. Often used in characterisation of tumours, diagnosing primary tumours,

Question 19

Mass spectrometry advantages

Answer 19

Very specific and sensitive, low cost consumables, wide range of analytes (mostly LMW)

Question 20

Mass Spec disadvantages

Answer 20

High one off cost, high skill, standardisation differs, interference possible

Question 21

Genomic Test

Answer 21

A test that uses nucleic acids to answer a diagnostic or prognostic question

Question 22

Cytogenetics

Answer 22

Karyotype 
FISH
Array CGH
Does this child have X syndrome?
Does this child have an identifiable chromosome problem?

Question 23

DNA sequencing

Answer 23

Can detect single or multiple gene mutations that predispose to disease