Often symptoms of some disease/infection are
quite plain to see in us humans and other animals e.g.
we experience a higher than normal temperature
due to some fever condition, a headache or a spotty rash.
But, what you see, feel or measure with a
thermometer, might not be enough to properly identify the infection
causing the disease.
And, particular problems arise if ...
(i) the symptoms are common to several
diseases,
(ii) or the symptoms are uncommon.
Therefore it is sometimes necessary to turn to
laboratory analysis of some kind e.g. blood tests or tissue cell
tests.
Samples of body fluids e.g. blood, faeces or
tissue from the diseased organism can obtained and visually examined
or analysed in various ways e.g.
(a)
Blood counts
The relative numbers of red blood cells or
white blood cells can be important symptoms and help diagnose
medical conditions.
A complete blood count is a blood test
used to evaluate your overall health and detect a wide range of
disorders, including anaemia, infection and leukemia.
If any of the measured concentration
of red blood cells, white blood cells (of the immune system) and
platelets is abnormal, further investigation would be requires.
(b)
Urine analysis
Urine analysis can detect urinal
infections, kidney or liver disease and diabetes (the latter is
indicated by too much glucose in urine - you can actually do a
simple dip stick test).
(c)
Detailed visual microscopic examination
of cells
Certain diseases can be detected by
examining tissue cells under an optical microscope to look for
abnormalities.
Cells of abnormal shape indicate the
presence of some disease.
Microorganisms such as bacteria can
detected and identified by their appearance.
You can stain the samples on the
microscope slide to help
show up clearer any specific cell or tissue abnormalities or
pathogens - the dye can latch onto and become concentrated on
particular structures.
(d)
Reproducing the pathogen for a more
detailed analysis
If the pathogen sample is too small, it
can be added to a growth medium to multiply and give a better
sample to analyse - either microscopic examination for
identification or from DNA analysis (see below).
See
Culturing microorganisms like bacteria for
more details of the aseptic techniques - to avoid contamination by
other microorganisms, therefore avoid identifying the wrong pathogen.
You can also test the
pathogen with a selection of antimicrobial compounds to see what
kills it - this can help identify the pathogen and what
treatment is most likely to be the most effective treatment.
(e)
Genetic analysis - DNA sequencing
The isolated suspect microorganism sample
can be subjected to DNA analysis.
The genetic profile can be matched
against a database of pathogen genomes.
Laboratory tests can identify a
specific pathogen by adding sections of DNA known to be
complementary to the pathogens DNA.
If the added DNA strands bind to the
pathogen's DNA, it means that specific pathogen is present,
thereby allowing identification.
