Blood Collection Tube for PCR Analysis
For peripheral blood intended for PCR analysis, use EDTA tubes (lavender/purple top), specifically K2EDTA or K3EDTA, as these are the standard anticoagulant tubes that preserve nucleic acids and prevent DNA degradation. 1, 2
Recommended Tube Specifications
EDTA tubes (lavender/purple top) are the gold standard for DNA/RNA preservation needed for PCR analysis, with K2EDTA at 1.5 ± 0.15 mg/mL blood being the preferred anticoagulant concentration 2
Collect at least 5 mL of blood in EDTA tubes to ensure sufficient specimen volume for nucleic acid extraction and PCR testing 1
Both K2EDTA and K3EDTA tubes are clinically equivalent for molecular testing, with spray-dried formulations preferred over liquid anticoagulants 3, 4
Critical Collection Technique
Immediately after blood collection, gently invert EDTA tubes 8-10 times (180-degree turns) to ensure proper mixing of blood with anticoagulant 1, 5
Fill tubes completely until the vacuum is exhausted to maintain the proper blood-to-anticoagulant ratio, as underfilling causes significant bias in results 1, 2, 6
Use a 21-gauge needle to minimize hemolysis and cellular damage that could compromise DNA quality 1, 5, 2
Processing Timeline
Process blood samples within 2 hours of collection when possible to minimize DNA degradation 1, 5, 2
If immediate processing is not feasible, refrigerate samples at 4°C for no longer than 24 hours before DNA extraction 1, 2
For cell-free DNA isolation (liquid biopsy applications), specialized EDTA tubes with cell stabilizers are commercially available to prevent nuclear DNA release from lysed cells 1
Common Pitfalls to Avoid
Never underfill EDTA tubes below 67% of nominal volume, as this creates an incorrect blood-to-anticoagulant ratio that can cause spurious results and DNA degradation 1, 2, 6
Avoid vigorous shaking or mixing, which can cause hemolysis and release of cellular contents that interfere with PCR 7
Follow proper order of draw if collecting multiple tube types: blood culture first, then sodium citrate, serum tubes, heparin tubes, EDTA tubes fifth, and finally sodium fluoride tubes to prevent cross-contamination of additives 1, 2
Do not use serum tubes (red/gold top) or heparin tubes (green top) for PCR analysis, as these are designed for different analytes and lack the DNA preservation properties of EDTA 5, 2