Selecting blood assortment tubes primarily is dependent upon whether or not you wish to acquire serum or plasma. Serum is the product of blood that has been allowed to clot. Plasma is the product of blood that has been prevented from clotting with an anticoagulant, whereas serum tubes include silica nanoparticles or thrombin to induce clotting. When utilizing plasma tubes, test that the anticoagulant is appropriate along with your downstream experiments.

Possibly you’re finding out blood cells utilizing hematology microscopy, or possibly you’re after genetic materials or circulating biomarkers. Whether or not you’re performing blood cultures or isolating regular B cells, it’s possible you’ll end up needing human blood samples. 

For a lot of scientists, getting blood specimens will be intimidating.

On this quick article, we clarify completely different blood assortment tube sorts, together with plasma tubes, serum tubes, and anticoagulant tubes, and their key variations.

Blood Assortment Tube Sorts

Whether or not you’re gathering your samples in-house or by a clinic, hospital, or pathology heart, you’ll must have a good suggestion of what sort of blood assortment tubes fit your functions. The very first thing to test is your protocol—for instance, some ELISAs will specify the varieties of samples you’ll be able to and may’t use with sure tubes. Fascinated about specimen necessities earlier than you get began can save quite a lot of complications later!

However what in case your protocol doesn’t specify, otherwise you’re adapting a technique from one other system, otherwise you wish to be sure to’re storing the perfect kind of pattern for future not-yet-defined analyses? Hopefully, I may help you discover your manner round all these otherwise coloured tubes.

A fast be aware about these cap colours earlier than we start: I’ve listed them under, and the color-coding system is usually fairly constant, however I can’t promise the colours are the identical in each firm producing blood assortment tubes, so at all times test first!

Serum vs. Plasma Tubes

The very first thing to determine is whether or not you wish to acquire serum or plasma. That is dependent upon whether or not or not it’s worthwhile to cease the blood from clotting.

Don’t confuse serum with plasma—whereas they’re each the liquid, cell-free a part of the blood you’ll be able to get hold of by centrifugation—they’re critically completely different:

• Serum is the product of blood that has been allowed to clot.
• Plasma is the product of blood that has been prevented from clotting with an anticoagulant.

Due to this fact, It is advisable to use both a serum assortment tube or a plasma assortment tube, respectively.

1. Serum Tubes

Blood serum is a good (and steady) manner of measuring the blood’s proteins, lipids, hormones, electrolytes, and many others. Many of those markers will be saved for days within the fridge or frozen down and measured in batches later.

There are two fundamental varieties of serum assortment tubes that differ in how they activate blood clotting, utilizing completely different clot activators.

Silica-Primarily based Tubes

These tubes have silica nanoparticles, which activate clotting by activating coagulation issue XII. Some even have a gel to separate the serum—for those who’re searching for a protein that isn’t concerned in coagulation, these are in all probability the tubes for you.

These with out the separating gel are often extra helpful in delicate diagnostic testing.

Be aware that their shade often is dependent upon their model. Becton Dickinson tubes are generally gold but additionally purple, whereas Greiner Bio-One tubes are purple. In comparison with thrombin-based tubes, it takes longer for blood to clot in silica-based tubes.

Clotting time: Roughly half-hour.

Thrombin-Primarily based Tubes

These tubes use thrombin to activate blood clotting. They’re primarily used clinically for exams which can be wanted particularly shortly. Nevertheless, some serum parts are rather less steady in these tubes.

Be aware that these tubes are often orange.

Clotting time: Roughly 5 minutes.

2. Anticoagulant Tubes

That is the class to think about for those who want cells or plasma (a cell-free liquid that also comprises coagulation components).

EDTA Tubes (Purple)

EDTA prevents clotting by chelating calcium, a vital part of coagulation. Relying on what you might be doing, EDTA in blood assortment tubes may very well be a catastrophe!

EDTA blood assortment tubes are your primary hematology tubes (by which I imply figuring out and counting blood cells, blood typing, and many others.).

Plasma saved from EDTA-treated blood may also be used to measure most proteins, and genetic materials can simply be saved from EDTA buffy coats (the interface between the purple cells and the plasma after centrifugation, containing white cells and platelets).

Be aware that these tubes include both K2EDTA (dipotassium) or K3EDTA (tripotassium). Beware that K3EDTA is extra hyperosmolar because of the additional potassium ion—which means it’s going to focus blood samples greater than K2EDTA through the hyperosmolar impact.

Sodium Citrate Tubes (Gentle Blue)

For coagulation and platelet perform exams. Like EDTA, citrate removes calcium from the blood by chelating it. Not like EDTA, it’s reversible—so calcium will be added again to review coagulation below managed situations. Citrated plasma can also be used to measure coagulation-relevant components.

It’s value noting {that a} citrate tube shouldn’t be the primary kind of tube crammed after venepuncture—the primary few mL of blood drawn might be a bit activated. Should you solely want samples collected in citrate blood assortment tubes on your venture, it is best to acquire a “discard” tube first.

Additionally, be aware that completely different citrate concentrations can be found from completely different firms, so test this before you purchase them.

CTAD Tubes (Additionally Gentle Blue)

CTAD stands for citrate, theophylline, adenosine, and dipyridamole. These aren’t frequent however are value understanding about—they forestall ex vivo activation of your platelets, making them helpful for some extra delicate platelet perform and coagulation research.

Be aware that CTAD is light-sensitive, so hold these guys at nighttime.

Heparin Tubes (Inexperienced)

These tubes can include both lithium heparin or sodium heparin. They’re much like serum clot activator tubes, however appropriate for exams in plasma moderately than serum. Like serum tubes, heparin tubes for blood assortment may have a separating gel. Heparin acts by inhibiting thrombin formation.

In case your endgame is PCR, you ought to be conscious that heparinized plasma samples might not be appropriate as heparin inhibits reverse transcription and PCR amplification, which means it could actually severely intervene with PCR reactions. [1]

Nevertheless, whichever anticoagulant you select, it’s possible you’ll want to permit for it in your response combine. You possibly can overcome heparin inhibition by treating your PCR combine with heparinase. Including a crowding agent resembling bovine serum albumin or diluting your PCR combine may work.

Sodium Fluoride Tubes

Sodium fluoride is an antiglycolytic agent (it prevents glucose metabolism), so these tubes are used for glucose and lactate testing. In addition they include an anticoagulant.

Acid Citrate Dextrose—ACD Tubes (Yellow)

These usually are not frequent, however they’re used for blood and tissue typing and DNA evaluation.

Sodium Polyanethol Sulfonate—SPS Tubes (Yellow)

SPS stabilizes bacterial development, so they’re helpful for microbiology functions.

Forms of Blood Assortment Tubes Summarized

For extra particular functions, there are further varieties of blood assortment tubes on the market, however hopefully, this has given you a deal with on the place to start out. Bear in mind to think about whether or not you need plasma or serum, and decide your tube accordingly.

Good luck along with your experiments, and welcome to the world of—let’s be sincere—feeling just a bit bit like a vampire.

Be aware: Please keep in mind to at all times put on protecting gear when working with blood, together with security goggles, gloves, and laboratory coats, and work rigorously to keep away from contact with blood and blood publicity. 

It’s essential to think about the security of your self and others within the lab. Watch the on-demand webinar on centrifugation to find the risks of aerosols from centrifugation and forestall them.

Initially printed Might 2015. Reviewed and up to date August 2023.

Reference

1. Kondratov Okay, Kurapeev D, Popov M, et al. (2016) Heparinase therapy of heparin-contaminated plasma from coronary artery bypass grafting sufferers permits dependable quantification of microRNAs. Biomol Detect Quantif 8:9–14