Principles and automation of biochemical testing

Question 1

The lab setting

Answer 1

Increased demand for testing and advancements in tech
General chemistry analysers
Immunochemistry analysers

Question 2

Automation is key to throughput

Answer 2

Rapid throughput is required to deal with increasing demands
Automation supports high throughput analysis
Turnaround time

Question 3

General chemistry systems

Answer 3

Commonly used techniques within these systems
Small bench top analysers - large freestadning analysers

Question 4

Spectroscopy

Answer 4

A=absorptivity
c = concentration
l = path length
Absorbance of substance will vary based on wavelength
If (a) is known concentration can be determined by measuring absorbance

Question 5

Cuvettes can be key

Answer 5

Normally standard path length
can be disposable or reusable
Different cuvettes have different ranges of wavelengths

Question 6

general chemistry analyser tests

Answer 6

Sample often have a range of tests conducted
Automation aims to facilitate multiple assays on one instrument
Requires maintenance

Question 7

Interfcae

Answer 7

Dedicated software for instruments
Require to define test parameters
defined by manufactures

Question 8

Specimens

Answer 8

Blood spectrums - serum or plasma
Other may be also used
presentations to instruments
Tubes

Question 9

Sample aliquoting and presentation

Answer 9

Primary sample - presented in machine
Separator gel - following centrifugation
Sample identification - barcoding
QC and calibration materials can also be presented to the machine
Priority samples - identified with ‘stat’ facility

Question 10

Pipetting

Answer 10

Defined volume of sample must be transferred accurately from the sample tube to the reaction tube to undertake testing

Question 11

Problems with fixed probes

Answer 11

Carry over - transfer of material from one sample to another
Haemolysed samples - integration of centrifugation and analysis steps make automated

Question 12

Reactions

Answer 12

Reaction vessel often consist of cuvettes, system temp controlled
Sequence often follows standard format
Types of reaction analysis - end of point reaction, kinetic reactions
Reagents - can be prepackaged, replenished as part of equipment, carry over for reagents
Mixing - mixer probes facilitate mixing

Question 13

Data

Answer 13

Types
Data printed out or transmitted to lab info systems

Question 14

Immunoassays

Answer 14

Antibodies raised against the analyse of interest bind it within a reaction sequence that can be monitored
Types of labels - enzymes, chemiluminescent molecules, fluorescent molecules
Two main types of immunoassay reaction - competitive, sandwich

Question 15

Competiivitive immunoassays

Answer 15

Use a limited concentration of antibody to produce a reaction in which the test antigen and a labelled antigen compete for a limited number of sites on a complementary antibody

Question 16

sandwich assay

Answer 16

Unknown analyte binds to an antibody
Analyte is washed before a second labelled antibody is added and attaches to bound analyte
Detection of labelled antibody is directly proportional to the level of analyte

Question 17

Enzyme linked ImmunoSorbent Assay (ELISA)

Answer 17

Simple automated immunochemistry systems may involve pipetting units for sample/ reagent pipetting, enabling automated ELISA
Most ELISA systems can be applied to most ELISA methods and are open platforms/systems - allow us of own reagents
Majority of immunochemistry analysers are closed systems

Question 18

Immunoanalysers

Answer 18

Some aspects similar to general analysers
Larger volumes as lower concentration of analyte
Carry over can causes issues due to potentially2 wide ranges of concentration between samples

Question 19

Integration and Tracking

Answer 19

Two strategies - link 2 or more analysers together, using a single sample presentation system, combine general chemistry and immunoassay units
Processing required for most samples before analysis
Sample preparation before analysis are pre analytical steps - centrifugation, cap removal, aliquoting, sorting
Analytical steps - process of analysis to produce results

Question 20

CSF Xanthochromia assay to support detection of Subarachnoid Haemorrhage (SAH)

Answer 20

Can be used to support investigation into a suspected subarachnoid haemorrhage (SAH) following an initial negative CT scan
SAH involves bleeding into the space and often results from rupture of an aneurysm in arteries within the space
CT scans are usually a front line tool to investigate SAH