Title: Introduction to Clinical
Biochemistry to specimen collection
1) To study the importance of Clinical Biochemistry.
2) To study the sample collection and labelling.
3) To identify the type and function of vacuum
learn the phlebotomy.
5) To identify the different size of syringe and
biochemistry is an area that concerned with biochemical changes in the body
such as imbalances of the composition of blood, stool, cerebral spinal fluid
(CSF) and urine. Determine the contents of the abnormal sample by testing it in
the laboratories. The result can aid doctors and scientists make an indication
or diagnosis if an organ in a normal condition.
1) There are few type of samples can be
collected for the diagnostic purpose. The most common samples that can be
collected are blood, urine, stool and CSF. First of all, the blood sample which
includes serum and plasma can be obtained from the patient through phlebotomy.
Phlebotomy is a process of blood drawing or introduces a fluid into a body by piercing
the vein and the process of piercing the vein known as venipuncture.
2) The procedures of phlebotomy
I. Position the patient in a proper and comfortable way. Then, ask the
patient to hyperextend his or her arm.
II. Apply the tourniquet three to four
inches above the puncture site. But, do not place the tourniquet too tightly or
too long (not more than two minutes) to prevent haemoconcentration from
III. Request the patient to make a fist without
pumping the hand.
IV. Select the suitable venipuncture site. The
available puncture site for venipuncture are the Median cubital vein, Cephalic
vein and Basilic vein.
V.Clean the patient’s arm by using
alcohol swab and allow it to air dry before puncture.
VI.Grasp the patient’s arm and palpate or feel for
VII.The needle should insert through the skin into
the vein in the form of 15 to 30-degree angle.
VIII.Filling the blood into the vacuum blood
collection tubes and remove the tourniquet during the filling of the last tube.
IX.Remove the needle from the patient’s arm
carefully and immediately press down on the gauze once the needle is removed
from the arm. Adequate pressure is required to press down to avoid the formation
of a haematoma.
X.Dispose the contaminated materials
in the designated containers (shark bin).
XI.Mix and label all the blood filling tubes once
finish filling the tubes.
3) For the size of needles that
suitable for venipuncture are usually needles that ranging from 21 to 25 gauge.
The smaller the needles gauze, the larger the diameter of the needle pore.
Thus, The 21 gauze needles considered as the standard venipuncture needle for
patients with normal veins and used primarily for large antecubital veins. 23
gauze needles usually for smaller antecubital, medium size forearm, veins of
hand and foot while the 25 gauze commonly use to collect blood from tiny veins
of premature neonates and infants. The 25 gauze needles rarely use in adults
except for hand veins of the adults. The sample collected by using this size
needles tend to be haemolysed than others.
4) The available size of the syringe are 1,3,5,10,
15 and 20 millilitre (ml). The size one and three ml is the most typical type
of syringe that used for venipuncture.
5) The table below shows the type and
function of vacuum blood collection tubes.
Anticoagulant in tube
Example of use
For tests that require serum, such
as most blood chemistries and serology tests.
Red or yellow
Act as serum separator tube, used
for tests that require serum.
For most haematological tests and
Lithium or sodium heparin
For some special chemistry tests, lymphocyte
studies, lupus erythematosus tests.
For most of the coagulation
Potassium oxalate or sodium
For certain glucose tests and
legal alcohol test.
Buffered sodium citrate
For erythrocyte sedimentation rate
6) Besides that, when a small amount of
blood is required, capillary puncture which also called as a finger stick or
heel stick test can be carried out. This can be carried out by poking the skin
with a lancet (a sharp needle) and collecting the blood drop onto a slide, test
strip or capillary tube. The best site for capillary puncture are the centre of
the third (middle) finger pad, or fourth (ring) finger of the hand while for the
heel stick capillary, foot lateral or medial plantar surface will be suitable.
7) The capillary tube or called as
haematocrit tube for the blood collection are available in blue, red and green
colour. The blue colour capillary tube
does not have any anticoagulant, red colour capillary tube consists of sodium
heparin while green colour capillary tube contains of ammonium heparin. After
collecting blood into the tube, the capillary tube or haematocrit have to
undergo centrifuge in order to get haematocrit value
8) When the capillary tube use to
collect serum bilirubin which is sensitive to light, it has to use clay or
plasticine to block the opening of the tube and centrifuge it in a dark room to
avoid false result occur.
9) Furthermore, urine is
also the sample that can collect for diagnosis purpose. A urine sample can be
collected in variety of ways according to the type of specimen required. The
most common three type of urine specimen are 24 hours urine, mid-stream urine
and fresh urine.
10) The 24 hours urine
sample is used to determine the quantity of solutes in the urine, for example
like proteins to prevent the solute diurnal variation which might affect the
result. The patient has to note the time of first and last void of the urine sample.
All the samples have to collect in a sterile, large, opaque container that
capable of holding four litres of sample until 24 hours are completed. 24 hours
urine specimen are used to measure the amount of creatinine, urobilinogen, protein,
11) Next, the
mid-stream urine (MSU) also known as clean catch sample. This method provides
the cleaner or less contaminated sample than the random sample for microscopic
analysis. It must only collect the centre part of urine stream but not first
and last part. It also has to use a sterile container to collect the sample. This
is because MSU mostly for microbiological culture and antibiotic susceptibility
testing so the presence of bacteria or normal flora on the genital part may
cause contamination of the sample and lead to a false result.
12) Fresh urine sample also called as a random
sample. This type of sample can collect at any time and without any precaution into
a small (at least 50ml) yellow cap bottle. This type of sample mostly for the screening test such as drug abuse
analysis. However, this type of sample is not considered as a best choice of the
sample due to its potential of diluting sample during sample collection.
13) Moreover, a stool is one of the
important samples for parasite and microbiology study. Procedures to collect
stool sample are placing the potty
in the toilet or spread clean newspaper over the toilet rim to catch the stool.
When collecting the stool, the patient has to use the spatula that comes with
the container and make sure the sample does not touch the inside of the toilet
to avoid contamination. If there is no
spatula been provided, the patient may use applicator stick instead. The
suitable amount of stool sample will be around a third of the container. The most
common container for stool collection is yellow cap cup.
14) Cerebral spinal fluid (CSF) is the
fluid that surrounds the brain and spinal cord. CSF is a very precious sample
due to it only can obtain a very small amount at one time and the process of
obtaining it is extremely painful. This painful process carries out on the
fully awake patient by experienced clinicians through lumbar puncture. Patient has
to sit straight and then injected a numbing medication into the back through the
skin. At the hip bones level, a thin needle is inserted into the back, between
the spine bones to get the spinal fluid. About two to three tablespoons of CSF are
required to collect into a sterile tubes for testing purpose.
15) Every sample must have a proper
label for the specimen identification. Mislabelled or unlabelled sample can
result in patient received wrong treatment or do not get the right treatment
that they need and cause irreversible consequences. The sample must have the specific
identifiers of the patient such as patient’s full name, date of birth, unique identifying
number (medical record number or barcode), time and date of collection, type of
specimen, test required and so on.
common sample that required for the diagnostic test are blood, urine, stool and
cerebral spinal fluid. Each of them has different collection method and
container to place the sample. Furthermore, a proper sample labelling is very
important for specimen identification.