Quick facts
- A microhaematocrit capillary tube collects a small, defined volume of blood by capillary action, is sealed at one end and is centrifuged to separate cells from plasma.
- The specification is three numbers: length, internal diameter and the additive, if any. Wall thickness and end finish follow from those.
- Canada: the tube itself carries no named device entry in the regulations, which classify by rule and by intended use rather than by product line.
- United States: the device entry is generic rather than tube-specific. Under 21 CFR 862.1675 a blood specimen collection device is Class II, and the identification names blood collection tubes and vacuum sample tubes among the examples.
- Glass versus plastic is a safety decision, not a preference. Glass tubes break; plastic tubes do not, and the trade-off is in filling behaviour and in how the tube reads after centrifugation.
- The specimen the tube produces is governed by transport law: Canadian acceptance criteria point to federal dangerous goods packaging, and the United States uses triple packaging under 49 CFR 173.199.
A capillary tube looks like a glass straw and behaves like a measuring pipette. The volume it collects depends on its internal diameter and on how completely it fills, which is why a tube specified by diameter alone is under-specified: two tubes of the same length and the same nominal size can deliver different volumes if the wall varies or if the fill is short.
This article covers the sizes, the materials, and the very different ways the two countries classify the device the tube belongs to.
What is a microhaematocrit capillary tube, and what do the dimensions control?
A microhaematocrit capillary tube is a thin tube that fills by capillary action when one end touches a drop of blood. After filling, one end is sealed, the tube is spun in a microhaematocrit centrifuge, and the packed cell column is read against a scale as a percentage of the total column.
The dimensions are not arbitrary. Length sets the centrifugal radius and the volume; internal diameter sets the volume per unit length; the additive coating, or its absence, sets what the sample can be used for afterwards.
| Tube type | Typical coat or additive | Typical use | What to check on the pack |
|---|---|---|---|
| Plain, glass | None | Haematocrit and samples read from the tube directly | Internal diameter, length, sealability |
| Heparinised, glass | Lithium heparin or ammonium heparin | Haematocrit plus some point-of-care chemistry | That the additive is declared and the fill volume is stated |
| Plain, plastic | None | Where breakage risk drives the choice | That the tube is certified for the centrifuge speed used |
| Heparinised, plastic | Heparin coating | Point-of-care work outside a centrifuge setting | Filling behaviour, which differs from glass |
The document that names the glass product family is ISO 12772:1997, whose title is Laboratory glassware — Disposable microhaematocrit capillary tubes. The title alone tells a buyer two things that matter: the standard covers glass, and it treats the tube as disposable performance rather than as reusable glassware.
Are capillary tubes classified the same way in Canada and the United States?
No, and the difference in structure is larger than the difference in class.
In the United States the entry is generic. 21 CFR 862.1675 identifies a blood specimen collection device as a device intended for medical purposes to collect and to handle blood specimens and to separate serum from nonserum (cellular) components prior to further testing, and states that this generic type may include blood collection tubes, vials, systems, serum separators, blood collection trays, or vacuum sample tubes. The same section classifies it as Class II.
That is a wide net by design: one entry covers a vacuum tube, a serum separator and a capillary tube, because the regulated function is collection and separation rather than the shape of the container.
In Canada, the Medical Devices Regulations, SOR/98-282 work from definitions and a rule set. An invasive device is defined by contact with the surface of the eye or penetration of the body, and Rule 2(1) of Schedule 1 places devices meeting that description in Class II. A capillary tube that is filled from a skin puncture and then centrifuged does not travel that route, so the classification follows the device's intended use and the general rules rather than a collection-tube line.
| Item | Canada | United States |
|---|---|---|
| Named entry for a collection tube | None; assessed by rule and intended use | 21 CFR 862.1675, blood specimen collection device |
| What the entry covers | The device as supplied and its intended purpose | Collection, handling and separation of serum from cellular components |
| Assigned class | Determined by the rules that apply to the device | Class II |
| Pre-market evidence | By class and licence application | By class, with the standard Class II expectation |
| Practising framework for the draw | Provincial laboratory licensing and employer duties | CLIA framework for the testing, OSHA for the draw |
The practical reading for a buyer is that a US supplier quoting 862.1675 is quoting a class, not a design specification. The design specification still has to come from the standard and from the manufacturer's declared fill volume.
Does the collection sequence differ between the two countries?
The chemistry does not change at the border, because the reference document is shared. The Clinical and Laboratory Standards Institute sets the order of draw, and its published summary explains both the sequence and one mechanism that is easy to miss.
According to CLSI's order of draw guidance, plastic serum tubes containing a clot activator may cause interference in coagulation testing, and only blood culture tubes, glass nonadditive serum tubes, or plastic serum tubes without a clot activator may be collected before the coagulation tube. The same page gives the familiar additive sequence, running from blood culture through citrate, serum, heparin, EDTA and then fluoride-oxalate.
That warning is where a capillary workflow and a venipuncture workflow diverge in practice: the tube material is part of the analytical chain, not a container choice. A laboratory that swaps a glass serum tube for a plastic tube with a clot activator in the collection order has changed the sequence, whether or not the worksheet says so.
The quality framework around the collection is also shared. ISO 15189:2022 specifies requirements for quality and competence in medical laboratories, applies to laboratories assessing their own competence and to bodies confirming or recognising that competence, and applies to point-of-care testing. On the United States side, the categories of tests by complexity sort tests into waived, moderate complexity including the PPM subcategory, and high complexity, while 42 CFR 493.15 describes the test systems eligible for a certificate of waiver. Where a laboratory introduces an unmodified, cleared test system, 42 CFR 493.1253 sets out the verification duties for accuracy, precision and reportable range.
| Item | Canada | United States |
|---|---|---|
| Order of draw reference | CLSI, shared with the United States | CLSI |
| Quality standard for the laboratory | ISO 15189:2022, plus provincial licensing | 42 CFR part 493 |
| Tiering of the test performed | Provincial licensing of the site | Waived, moderate and high complexity |
| Verification duty | Set by the quality standard and accreditation body | 42 CFR 493.1253 for unmodified cleared systems |
| Quality control materials | Assessed by intended use | 21 CFR 862.1660, quality control material, Class I |
The collection itself carries a safety duty. In the United States the bloodborne pathogens standard is published by OSHA, and Canadian guidance on sharps handling and needlestick injuries is published by the Canadian Centre for Occupational Health and Safety on needlestick injuries. The World Health Organization's guidelines on drawing blood and phlebotomy cover the procedural side, and its laboratory biosafety manual covers containment.
How does the specimen leave the building, and what governs that?
Once a capillary sample is sealed and labelled, it becomes a specimen in transit, and the two countries write that journey differently.
Public Health Ontario's specimen acceptance criteria require that specimen packaging meet the minimum federal Transportation of Dangerous Goods packaging requirements and that the specimen not be leaking, and they set out the identity requirements that trigger a signed waiver where identifiers are missing, incomplete or conflicting between specimen and requisition. The test information index carries collection and handling requirements per test, and the kit and test ordering instructions cover the ordering side.
The United States treats the same shipment as a hazardous material. Under 49 CFR 173.199 a Category B infectious substance must be in triple packaging made up of a primary receptacle, a secondary packaging and a rigid outer packaging, with the outer packaging carrying the UN3373 square-on-point mark and the proper shipping name.
| Item | Canada | United States |
|---|---|---|
| Transport law | Transportation of Dangerous Goods Regulations | 49 CFR hazardous materials regulations |
| Packaging criterion in lab documents | Packaging meets the minimum federal TDG packaging requirements | Triple packaging: primary, secondary, rigid outer |
| Leak criterion | The specimen must not be leaking | Performance-based, verified by drop test |
| Identifier failure | Signed waiver required, otherwise the test is cancelled | Laboratory rejection criteria |
| Marking | Means-of-containment approach | UN3373 diamond plus the proper shipping name |
Which consumables does a capillary collection point actually use?
A capillary collection is short, but it draws on a specific list, and each item has a specification.
- Lancets. The puncture device sets the drop size. Sterile blood lancets are bought by gauge, and the gauge determines how much blood arrives and how much squeezing is needed.
- The tubes themselves. Plain or heparinised, glass or plastic, specified by internal diameter, length and additive. Specify the fill volume, not only the diameter.
- Sealing compound or caps. An unsealed tube leaks in the centrifuge, and a leaking tube in a centrifuge is a contamination event rather than a re-run.
- Swabs and wipes. Collection points consume swabs continuously. Double-tipped cotton swabs and foam-tipped swabsticks cover the sampling bench and the collection tray.
- Primary containers for larger samples. Where the visit also collects urine or a swab, a graduated specimen cup is the primary receptacle.
- Transport packaging. 95 kPa specimen transport bags have to be part of a system documented against the applicable standard, with a separate compartment so the requisition never sits against the specimen.
- Centrifuge consumables. Where a laboratory tubes rather than uses a capillary, centrifuge tubes are the same purchasing family and are specified by volume and sterility.
For a clinic or laboratory buying these lines together, the ordering route is worth setting up once.
Sources
- ISO 12772:1997, disposable microhaematocrit capillary tubes
- ISO 15189:2022, medical laboratories
- 21 CFR 862.1675, blood specimen collection device
- 21 CFR 862.1660, quality control material
- 42 CFR 493.5, categories of tests by complexity
- 42 CFR 493.15, laboratories performing waived tests
- 42 CFR 493.1253, verification of performance specifications
- 49 CFR 173.199, Category B infectious substances
- CLSI, order of blood draw tubes and additives
- CLSI, quality management systems
- PHO, specimen acceptance criteria
- PHO, test information index
- PHO, kit and test ordering instructions
- Medical Devices Regulations, SOR/98-282
- WHO guidelines on drawing blood and phlebotomy
- WHO, Laboratory Biosafety Manual
- OSHA, bloodborne pathogens
- CCOHS, needlestick injuries
- American Society for Microbiology
Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers account setup and case pricing, and the B2B wholesale collection lists the lines stocked for institutional buyers. Laboratories that also run an in-house sterilizer can start with the biological indicator 5-pack trial.
Related reading
- Centrifuge tubes: 15 mL vs 50 mL when stocking a clinic laboratory
- Sterile specimen containers: leak testing and labelling
- Specimen collection containers for Canada: urine cups and 24 hour collection
- Does TDG apply to specimen collection in Canada?
- 95 kPa specimen bags vs 3 wall transport bags
Frequently Asked Questions
Are capillary tubes classified the same way in Canada and the United States?
No. The United States uses a generic entry: 21 CFR 862.1675 identifies a blood specimen collection device as a device intended to collect and handle blood specimens and to separate serum from nonserum components, naming blood collection tubes and vacuum sample tubes as examples, and classifies it Class II. Canada classifies by the rules in Schedule 1 of the Medical Devices Regulations applied to device definitions and intended use, with no collection-tube-specific entry.
What dimensions should a capillary tube specification state?
Length, internal diameter and the additive, and then the fill volume the manufacturer declares. Internal diameter drives volume per unit length and wall thickness, so a specification that states only a nominal size is under-specified. Whether the tube is glass or plastic matters too, because it changes breakage risk and filling behaviour.
Which standard covers glass microhaematocrit capillary tubes?
ISO 12772:1997, titled Laboratory glassware — Disposable microhaematocrit capillary tubes. The title establishes two things a buyer can rely on: the standard covers glass, and the tube is treated as a disposable product rather than as reusable glassware.
Does the order of draw change between Canada and the United States?
No. The reference document is shared: the Clinical and Laboratory Standards Institute sets the additive sequence and warns that plastic serum tubes containing a clot activator may cause interference in coagulation testing, so only blood culture tubes, glass nonadditive serum tubes, or plastic serum tubes without a clot activator may be collected before the coagulation tube.
How does a capillary specimen have to be packaged for transport?
Canadian laboratory acceptance criteria require that the packaging meet the minimum federal Transportation of Dangerous Goods packaging requirements and that the specimen not be leaking. In the United States a Category B infectious substance must be in triple packaging made up of a primary receptacle, a secondary packaging and a rigid outer packaging under 49 CFR 173.199.
What laboratory consumables sit around a capillary collection?
Lancets specified by gauge, the tubes themselves with their sealing compound or caps, swabs for the collection bench, a primary receptacle for any larger sample taken at the same visit, transport packaging documented against the applicable standard, and centrifuge consumables where the laboratory tubes rather than uses a capillary.
CliniEco Medical supplies specimen collection and transport consumables, laboratory lines and the wider clinical catalogue described in this article. Health Canada MDEL #35334. This article is written for laboratory, clinic and procurement professionals and is not clinical guidance; method selection and result interpretation belong to the laboratory director.
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