Preservation of cell-free RNA in blood samples
A method for preserving and processing cell-free nucleic acids located within a blood sample is disclosed, wherein a blood sample containing cell-free nucleic acids is treated to reduce both blood cell lysis and nuclease activity within the blood sample. The treatment of the sample aids in increasing the amount of cell-free nucleic acids that can be identified and tested while maintaining the structure and integrity of the nucleic acids.
1. A direct blood draw tube for stabilization of cell-free nucleic acid within a plasma sample comprising:
a composition including:
a) one or more preservative agents including imidazolidinyl urea;
b) one or more enzyme inhibitors; and
c) one or more solvents; and
wherein the one or more enzyme inhibitors are selected from the group consisting of EDTA, aurintricarboxylic acid, and combinations thereof;
wherein an amount of the one or more preservative agents relative to an amount of the one or more enzyme inhibitors is about 3 to about 6 parts by weight of preservative agent to about 2 parts by weight of enzyme inhibitors;
wherein the composition contains less than, or about 30% by weight of the one or more enzyme inhibitors;
wherein the composition includes some formaldehyde but less than 500 parts per million of formaldehyde; and
wherein a concentration of the preservative agent is less than, or about 1000 g/l of the composition; and
wherein the direct blood draw tube including the composition and a blood sample located therein is storable at room temperature.
2. The direct blood draw tube of claim 1 , wherein the composition is present in an amount of at least, or about 200 g/liter.
3. The direct blood draw tube of claim 1 , wherein the composition is present in an amount of less than, or about 300 g/liter.
4. The direct blood draw tube of claim 1 , wherein the enzyme inhibitor includes only EDTA.
5. The direct blood draw tube of claim 1 , wherein the cell-free nucleic acid is RNA.
6. The direct blood draw tube of claim 1 , wherein the concentration of the preservative agent is at least, or about 50 g/liter.
7. The direct blood draw tube of claim 1 , wherein the concentration of the preservative agent is less than, or about 500 g/liter.
8. The direct blood draw tube of claim 1 , wherein the composition is substantially free of guanidinium salts, sodium dodecyl sulfates, or combinations thereof.
9. The direct blood draw tube of claim 1 , wherein the one or more enzyme inhibitors are present in an amount sufficient to prevent nuclease activity from reducing an amount of recoverable cell-free RNA by more than 15%.
10. The direct blood draw tube of claim 1 , including imidazolidinyl urea and EDTA in a buffered salt solution.
11. The direct blood draw tube of claim 1 , including at least, or about 1% by weight or more EDTA.
12. The direct blood draw tube of claim 1 , wherein an amount of composition is combined with a 5 ml blood sample so that any consequential dilution of the sample is substantially avoided, and cell-free nucleic acid in the sample are not materially diluted.
13. The direct blood draw tube of claim 1 , wherein the cell-free nucleic acid is DNA.
14. The direct blood draw tube of claim 1 , wherein the imidazolidinyl urea is present in an amount of about 200 g/l to about 500 g/l.
15. The direct blood draw tube of claim 1 , wherein the preservative agent includes sodium hydroxymethyl glycinate.
16. The direct blood draw tube of claim 1 , wherein the composition includes one or more polyamines.
17. The direct blood draw tube of claim 1 , wherein the solvent is selected from the group consisting of: water, saline, dimethylsulfoxide, alcohol and any mixture thereof.
18. The direct blood draw tube of claim 1 , wherein the composition is in a form of a film, gel or other substantially solid or highly viscous layer.
19. The direct blood draw tube of claim 1 , wherein the composition is storable at room temperature.
20. The direct blood draw tube of claim 1 , wherein the direct blood draw tube is comprised of a transparent material and an interior wall of the tube is coated or otherwise treated to modify its surface characteristics.