K2 EDTA Vacuum Blood Collection Tubes (Purple/Lavender Top)
Lab Supplies

K2 EDTA Vacuum Blood Collection Tubes (Purple/Lavender Top)

Pack Sizes Available

100 tubes per box — standard format
Available volumes: 2ml, 3ml, 4ml, 5ml, 6ml (specify at order)
Tube sizes: 13 x 75mm or 13 x 100mm depending on volume

Product Description

Collecting a blood sample correctly is the foundation of every laboratory result that follows from it. The tube, the anticoagulant, the draw volume, the mixing protocol — all of it matters. An error before the sample reaches the analyser is invisible. The result looks like a result. It is wrong, and no one in the laboratory chain of custody can know it without re-drawing. Pre-analytical quality is underappreciated precisely because its failures are silent. K2 EDTA vacuum blood collection tubes are the most widely used haematology collection tube in clinical laboratories globally. The K2 designation refers to dipotassium EDTA, supplied as a dry powder or spray coating on the inner wall of the tube. When blood enters the evacuated tube, the EDTA dissolves into the sample and immediately chelates the free calcium ions in the plasma, stopping the coagulation cascade at its earliest step and preserving the cellular elements in their original state for analysis. The internationally standardised lavender/purple cap identifies the tube as an EDTA tube across all phlebotomy systems, enabling accurate tube identification during multi-tube collection protocols where several different tube types are drawn from the same venepuncture. The draw order (sodium citrate before EDTA before serum tubes) is a specific requirement of phlebotomy protocols, and the colour-coding system supports this. K2 EDTA spray-coating provides a uniform anticoagulant distribution with no liquid volume added to the sample, which means the EDTA-to-blood ratio dilution effect is essentially zero compared to liquid K3 EDTA formulations. CLSI and ICSH guidelines cite this as the reason K2 is slightly preferred for automated haematology analysis where cell count reference ranges are calibrated against samples without dilution correction. For laboratory supply distributors, K2 EDTA tubes are one of the highest-frequency consumable items in any product catalogue. Sara Wellness exports laboratory phlebotomy consumables to medical distributors internationally.

Technical Specifications

  • Anticoagulant: K2 EDTA (dipotassium EDTA) — dry spray coating on inner tube wall; no dilution of sample
  • Cap/Stopper Colour: Lavender/Purple — internationally standardised colour code for EDTA
  • Available Draw Volumes: 2ml, 3ml, 4ml, 5ml, 6ml (pre-evacuated to nominal draw volume)
  • Tube Dimensions: 13 x 75mm (2-4ml) or 13 x 100mm (5-6ml)
  • Pack Size: 100 tubes per box
  • Guideline Preference: CLSI H3-A preferred anticoagulant for automated haematology analysis
FAQ

Frequently asked questions

K2 EDTA is a dry additive applied as a spray coating on the inner tube wall. It adds no volume to the blood sample when it dissolves, meaning there is no dilution effect. K3 EDTA is a liquid solution that adds a small volume to the collected sample, causing a slight dilution of all cellular parameters. CLSI H3-A guidelines recommend K2 EDTA as the anticoagulant of choice for haematology, as the calibration of automated haematology analysers assumes no dilution correction is needed. For most routine CBC tests the difference is clinically insignificant, but for sensitive reference range work K2 is the guideline preference.

If less blood is drawn than the tube's nominal draw volume, the EDTA concentration relative to the blood volume is higher than intended — this is called under-filling. Excess EDTA causes cell shrinkage due to osmotic effects, reducing mean cell volume (MCV) and haematocrit readings, and can cause falsely low platelet counts due to EDTA-induced platelet clumping. Under-filled tubes should be discarded and the sample re-drawn. The pre-determined vacuum in the tube is calibrated to draw exactly the correct volume for the amount of EDTA present.

The recommended draw order per CLSI guidelines is: blood culture bottles first, then sodium citrate tubes (blue top), then serum tubes with gel separator (yellow/red top), then heparin tubes (green top), then EDTA tubes (lavender top), then fluoride/oxalate tubes (grey top) last. Drawing EDTA before citrate tubes would contaminate the citrate sample with EDTA, which interferes with coagulation testing. Following the correct draw order is essential when multiple tube types are collected from the same needle.

Yes. EDTA tubes — both K2 and K3 — are suitable for DNA-based molecular testing including PCR, whole genome sequencing, and viral load quantification assays. EDTA preserves the integrity of nucleated white blood cells (the source of DNA in whole blood samples) and inhibits DNases, making it the standard collection tube for genetic and molecular diagnostic testing. Specific molecular assays may have their own tube requirements, so the specific test requisition should always be checked before collection.

Yes. EDTA tubes (both K2 and K3) are the standard collection tube for blood group and cross-matching testing in blood banking. The anticoagulant preserves red cell antigens in their native state for several days at 2-8°C refrigerated storage, which is essential for serological testing. Most blood bank protocols specify EDTA as the anticoagulant of choice for all pre-transfusion testing samples. Clotted (serum) samples are not suitable for blood banking as cell agglutination reactions used in serological testing require intact red cells.

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