Bilbate Ltd - Patented Spirocap Capillary

Straight and Spiral Filament Glass Capillary Tubes Patent No: 2136899A The present invention relates to capillary tubes. More particularly, but not exclusively, it relates to an improved capillary tube for use in the storage and testing of blood samples. When blood samples are taken from humans or animals for subsequent testing, it is usually necessary to treat the blood samples to prevent them coagulating before they can be tested. An ant-coagulant, such as heparin or the lithium salt of heparin, is conventionally added to the blood samples for this purpose. Other regents may also be added, such as ethylene diamine tetra-acetic acid (EDTA) for measuring a platelet count and making blood films. The amount of blood required for most modern blood testing procedures is very small, particularly when a test is based on reactions with antibodies, or other biochemical reactions. It is therefore a standard technique that when a blood sample has been taken from a subject, to take part of the blood up into a capillary tube, where it may be stored until required. The anticoagulant is conveniently and safely added to the blood by coating the interior surface of the capillary tube with anticoagulant before use. When blood is taken up into the tube, the anticoagulant dissolves into the blood and prevents premature coagulation. It is normal to roll the capillary tube about its longitudinal axis to improve the mixing of the anticoagulant with the blood. There are however problems with this technique. The anticoagulant is coated on the interior surface of the capillary tube by taking up into the tube a solution of the anticoagulant, which is the allowed to dry. This can coat the interior surface unevenly, sometimes to the extent that a solid plug of anticoagulant forms, blocking the capillary tube and making it useless. Such tubes must be checked for and discarded.

Colour-Coded Spirocap Capillaries

The anticoagulant does not always mix rapidly and evenly into the blood within the tube, despite the tube being rolled. This can lead to partial coagulation of the blood sample, which thereby becomes useless.

When a capillary tube is intended to be used with blood samples in hot and particularly tropical climates, it is normal to coat the interior of the tube with at least a double dose of anticoagulant. The above problems are thereby exacerbated.

Although the natural 'capillary rise' of liquids into a capillary does assist the transfer of blood into the capillary tube, the surface tension and viscosity of blood are such that this capillary action is limited and slow. A large part of the capillary tube must be dipped into the blood sample in order to fill the tube, and a user must wait until the blood has climbed up the tube to the required level. This is inconvenient when taking large numbers of samples. A finer tube would produce a higher capillary rise, but would restrict the quantity of blood that could be stored, would not increase the speed of the capillary rise and would make the tube more fragile.

Fragility is a problem, even with stouter capillary tubes. The tubes are handled manually, so any breakages are a safety risk, both from the broken glass and from any pathogens which may be present in the blood sample. Further processing, such as centrifuging, may also be carried out while the blood sample is being stored in the capillary tube. This is another point at which breakages are to be avoided, because of sample loss, because of possible contamination of other samples being processed and because of risks from blood-borne pathogens. (Blood testing for AIDS, hepatitis and other such disease is carried out on samples stored in capillary tubes).

There is a need in the field of blood testing for a form of capillary tube that would obviate the above problems. It can also readily be seen that similar problems would arise in other scientific fields, such as chromatography, in which capillary tubes are employed.

It is therefore an object of the present invention to provide an improved form of capillary tube which serves to obviate the above problems and permits faster, more reliable and safer handling of samples, more particularly blood samples.

Spirocap benefits derive from its faster capillary rise with quicker mixing with lower levels of anticoagulant required. This helps avoid the clogging problems associated with standard capillaries. These desirable properties combined as they are with a greater mechanical strength and elimination of the need for agitation of the tube to encourage anticoagulant mixing make for a major advance in blood sample collection. The original capillary tube was specifically developed for a Belgian client who manufactures blood collecting kits for use in Congo, where adverse climatic conditions made collecting in the field difficult to obtain a 100% success rate. After 3 years in use the Spirocap capillary achieves 100% pass mark at a rate of 100000 tests per month.

Since the introduction to the market many other uses have been found to exploit the tubes unusual properties and for techniques other than it was originally designed. Bilbate is now able to incorporate the system across the whole of its capillary range and welcomes the opportunity to develop unusual applications with any interested parties.

Spirocap are manufactured with 1-4 filaments as standard. The pitch of the spiral is selective and usually requested by the end user. Filaments are equally spaced inside the bore of the tubing; single filament, double filament 180° apart, triple filament 120° apart and quadruple 90° apart.

Borosilicate Glass - Straight filament - for Spiral filament add SF to the code.

Bilbate Ltd, 24 High March, Daventry, Northamptonshire NN11 4HB, UK
Tel: +44 (0)1327 705113 or +44 (0)1327 871467, Fax: +44 (0)1327 300619