Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to a method of
introducing a liquid into a tube and to a device
for use in the method. More particularly the invention has
been devised in connection with a method of determining the
erythrocyte sedimentation rate of a blood sample.
In the diagnosis of blood disorders, the rate at
which erythrocytes (red corpuscles) settle out of a blood
sample is commonly used as a primary indicator of whether
or not the sample is normal. The sample is placed in a
calibrated measuring tube and allowed to stand for a pre-
determined length of time, after which noteis taken of the
extent to which the erythrocytes have settled out. In a
blood sample containing, say, hepatitus virus, the erythro-
; cytes will settle to a significantly greater extent than
in the case of a normal blood sample.
Techniques previously used for introducing a
blood sample into a measuring tube have had significant
shortcomings. For example, in one case, the blood is
; aspirated into the tube by mouth; however, this has therisk that the technician performing the technique is
exposed to possiblè contamination by viruses and the
¦ like in the blood. Mechanical aspirator devices used
~i to`avoid this problem are often difficult to manipulate
and do not allow blood to be raised in a steady and
controlled fashion, with the result that spillage and
contamination of blood samples often occurs.
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For example, United States Patent No. 3,373,601
(Monn) discloses a device comprising a container for a
blood sample and a calibrated tube which can be inserted
into and slid axially of the container. The container
has an annular lip which seals against the wall of the
` tube so that, when the tube is pushed into the container
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it acts in the manner of a piston, forcing the
blood up into the tube. The problem with this device ;,
is that, unless extreme care is taken to slowly and
carefully push the tube into the container, the tube
will be displaced too quickly and the blood will rise
rapidly in the tube and squirt out of its open upper
end. This is not only highly inconvenient and unhygienic,
but is also potentially dangerous since the blood sample
may be contaminated. -
Broadly considered, an object of the present inven-
tion is to provide an improved method of introducing a
liquid into a tube. A more particular object is to
provide an improved method of determing the erythrocyte
sedimentation rate of a blood sample.
According to a first aspect of the invention,
there is provided a method of introducing a liquid into
a tube. The method involves a first step of providing
a device comprising: an elongate transparent tube which
is open at both ends and a cap fitted to a first end
portion of the tube. The cap has a closed top and a
skirt which depends from said top and which makes air-
tight sealing engagement with the tube. The cap is
slidable along the tube from a first position to a second
position closer to the first end of the tube than the
first position while maintaining said airtight sealing
1 engagement. The next steps are to arrange the cap at
,~ its said first position and immerse a second end portion
of the tube in a liquid. While maintaining the second
' end of the tube immersed in the liquid, the cap is then
slid along the tube towards its said second position to
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an extent sufficient to cause liquid to be drawn up the
tube to the level of an appropriate one of the graduations.
The tube is then remo~ed from the liquid. The lumen of
the tube is dimensioned so that the column of liquid is
retained in the tube.
According to another aspect of the invention,
there is provided a method of determining the erythro-
cyte sedimentation rate of a blood sample. The method
involves a first step of providing a device comprising:
an elongate transparent tube which is open at both ends
and a cap fitted to a first end portion of the tube.
The cap has a closed top and a skirt which depends from
said top and which makes airtight sealing engagement
with the tube. The cap is slidable along the tube from
a first position to a second position closer to the
first end of the tube than the first position while
maintaining said airtight sealing engagement. The
next steps are to arrange the cap at its said first
position and immerse a second end portion of the tube
in the blood sample. While maintaining the second end
of the tube immersed in the blood sample, the cap is
then slid along the tube towards its said second position
to an extent sufficient to cause blood to be drawn up the
tube to an appropriate level. The tube is then removed
from the blood sample and maintained in an upright position
with the first end portion of the tube uppermost for a
predetermined length of time. The lumen of the tube is
dimensioned so that the column of blood is retained in
the tube. After the predetermined length of time, the
extent to which erythrocytes in the blood have settled is
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determined and provides an indication of the erythrocyte
sedimentation rate of the blood sample.
The invention also provides a device for use
in performing the method.
In order that the invention may be more clearly
understood, reference will now be made to the accompany-
ing drawings which illustrate one embodiment of the in-
vention, by way of example, and in which:
Fig. 1 is a perspective view of the device
according to the invention immersed in a blood sample;
Fig. 2 is a view similar to Fig. 1 and illus-
trates the manner in which a column of blood is raised
in the device;
Fig. 3 is a perspective view showing the device
supported in a rack during sedimentation of erythrocytes
in the blood sample; and,
Fig. 4 is an exploded longitudinal sectional
view through the device.
Referring first to Figs. 1 and 2, a device for
use in determining the erythrocyte sedimentation rate of
a blood sample is indicated generally by reference nu-
meral 10. Device 10 includes an elongate transparent
tube 12 and a cap 14. Tube 12 is open at first and second
. . . . . . . .
ends 16 and 18 respectively and is marked with a series
' of graduations which extend longitudinally of the tube 12
` and which are generally denoted 20. In this embodiment
the graduations are in millimeter5 and tube 12 is made
of plastic.
Cap 14 .is a one-piece plastic moulding and is
` 30 fitted in airtight fashion to the first end portion of
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the tube 12. The cap includes a closed top 21 and a de-
pending generally cylindrical skirt 22 which makes airtight
sealing engagement with the external surface of the tube
12. As can best be seen in Fig. 4, skirt 22 is formed
with two internal sealing ribs 24 of annular form which
engage the external surface of tube 12 and which actually
provide the seal between the cap and the tube. Ribs 24
are generally wedge-shaped in cross-section and taper
towards top 21 of the cap. The ribs permit cap 14 to
be slid longitudinally along the tube 12 while main-
taining said airtight sealing engagement. Cap 14 is
slidable along the tube from a first position to a second
position closer to the first end 16 of tube 12. The cap
is shown in typical fixst and second positions in Figs.
1 and 2 respectively.
When the device is to be used to determine the
erythrocyte sedimentation rate of a blood sample, cap 14
is initially positioned at a suitable first position such
as that shown in Fig. 1. The lower (second) end portion
of the tube is then immersed in a blood sample as shown
in that view. The sample is indicated at 26 and is con-
tained in a laboratory flask denoted 28. While the lower
(second) end portion of the tube is maintained immersed
in the blood sample, cap 14 is slid along tube 12 towards
its upper (first) end. This causes a column of blood
to be drawn up into tube 12. Cap 14 is moved along tube
12 to an extent sufficient to draw the column of blood
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` up to the level of an appropriate one of the graduations.
In Fig. 2, the blood level is indicated at 30 and is at
the level of the "0" graduation 20. However, it will be
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appreciated that any appropriate graduation may be se-
lected. It will also be realized that the specific lo-
cations of the cap 14 in its said "first" and "second"
positions are not critical. It is merely necessary that
the extent to which the cap is moved be sufficient to
draw a column of blood into tube 12 and up to the level
of an appropriate one of the graduations.
It will be seen from the drawings that the skirt
22 of cap 14 is outwardly flared in the region of its open
end just below the ribs 24 as indicated at 22a, and
terminates in a shoulder 32. This shoulder allows
a person usin~ the device to grasp the tube 20 between
the fingers and palm of one hand and push the cap
upwardly on the tube using the thumb of the same hand.
This makes for convenient one-handed operation of the
device.
After the column of blood has been drawn into
the tube 12 of the device as described, the tube is re-
moved from the blood sample and the device is maintained
in an upright position with its first end 16 uppermost,
for a predetermined length of time. It will of course
be appreciated that the lumen of the tube 12 is dimen-
sioned to ensure that the blood is retained in and does
not escape from the tube at this time. In Fig. 3, part
of a suitable supporting rack for the device is shown at
34. It will be seen that the rack includes a series of
openings through one of which the tube 12 is inserted
and which is'd~mensioned so that the device is supported
by abutment of the shoulder 32 of cap 14 against the
rack.
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After the expiry of a predetermined length of
time, the extent to which erythrocytes in the blood in
tube 12 have settled is determined by reference to the
graduations 20. For example, in Fig. 3, the level of the
erythrocytes is indicated at 36 and the level of the sam-
ple as a whole at 38; the difference in levels is repre-
sented by clear blood plasma. Thus, in the present case,
it will be seen that the erythrocyte level has dropped by
20 millimeters in the said predetermined length of time.
On the basis of this figure, the erythrocyte sedimentation ::
rate of the blood sample can be calculated and a deter-
mination made as to whether or not the sample is abnormal.
In some cases, it may be desirable to dilute
the blood sample using a sodium citrate solution before
determining the sedimentation rate of the sample. The
sodium citrate solution acts as an anti coagulent in the
sample. Where this is to be done,.the device:..p.ro.vided.by the
invention may also be used to introduce the sodium citrate
solution into the sample. Thus, by immersing the lower
end of the tube of the device in a body of sodium citrate
solution in a container and sliding the cap upwardly as
:~ described above, a predetermined volume of solution can
be drawn into the tube and subsequently discharged inbo
the blood sample by depressing the cap and thereby
ejecting the blood sample from the lower end of the tube.
: It will of course ~e appreciated that the
preceding description relates to a specific embodiment
: of the invention and that the invention is not limited
to the particular form of the invention described with
reference to the drawings. Thus, the invention may be
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used for introducing any appropriate liquids other than
blood samples into measuring tubes and for transferring
those liquids to other vessels as required. Examples of .
detail changes are that, although a plastic tube has been
described, the tube could of course be made of glass. .
The grauduations on the tube could be differently arranged
and need not be numerically identified. Also, variations
in the form of the cap are possible.
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