Preservation of fetal nucleic acids in maternal plasma

1. A method for stabilizing, storing, isolating and analyzing cell-free fetal nucleic acid comprising:

drawing a blood sample including a plasma containing donor cellular nucleic acid and cell-free nucleic acid including cell-free fetal nucleic acid directly into an evacuated blood collection tube containing about 0.05 ml to 1.0 ml of a protective agent wherein the protective agent is a solution formed from ingredients including:

a) 0.1 to 3 g/ml of imidazolidinyl urea;

b) glycine; and

c) EDTA;

wherein an amount of imidazolidinyl urea relative to an amount of glycine is 10 parts by weight of imidazolidinyl urea to 1 part by weight glycine; storing the blood sample including the plasma for 1 to 14 days,

separating the plasma from the blood sample;

isolating the cell-free nucleic acid-from the plasma of the stabilized blood sample;

and analyzing at least the cell-free fetal nucleic acid isolated from the plasma of the stabilized blood sample;

wherein the blood sample and the plasma is not frozen prior to the step of isolating.

2. The method of claim 1 , wherein the analyzing step includes contacting the cell-free fetal nucleic acid with an enzyme, an amplifier or both.

3. The method of claim 1 , wherein the evacuated blood collection tube into which the blood sample is drawn includes a polymeric coating on an interior of the tube.

4. The method of claim 1 , wherein a concentration of the imidazolidinyl urea within the protective agent prior to the drawing step is between 0.4 g/ml and 0.8 g/ml.

5. The method of claim 2 , wherein an amount of imidazolidinyl urea within the protective agent and upon contact with the blood sample is less than about 20 mg/ml of the total combined blood sample and protective agent.

6. The method of claim 1 , wherein the step of storing is at room temperature.

7. The method of claim 1 , wherein the protective agent prior to the drawing step contains less than 1000 parts per million formaldehyde.

8. The method of claim 6 , wherein the protective agent prior to the drawing step contains less than 1000 parts per million formaldehyde.

9. A method for stabilizing, storing and isolating cell-free fetal nucleic acid comprising:

contacting a drawn blood sample containing donor cellular nucleic acid and cell-free nucleic acid including the cell-free fetal nucleic acid with a protective agent that is a solution formed from ingredients including:

(i) about 300 g/l to about 700 g/l imidazolidinyl urea;

(ii) about 20 g/l to about 60 g/l glycine; and

(iii) about 60 g/l to about 100 g/l of EDTA;

wherein the solution includes a solvent;

allowing a period of time to lapse; and

after the period of time has elapsed, separating a plasma from the drawn blood sample and isolating the cell-free nucleic acid from the plasma, wherein the cell-free nucleic acid is free of cell-free nucleic acid attributable to apoptosis, cell death and lysis of nucleated maternal blood cells post blood draw.

10. The method of claim 9 , wherein the period of time is at least 24 hours without freezing of the contacted drawn blood sample.

11. The method of claim 4 , wherein the evacuated blood collection tube containing the protective agent receives about 10 ml blood.

12. The method of claim 1 , wherein the step of storing is for 7 to 14 days.

13. The method of claim 9 , wherein the period of time is 7 to 14 days, without freezing of the contacted drawn blood sample.

14. A method for stabilizing, storing, isolating and analyzing cell-free fetal nucleic acid comprising:

drawing about a 10 ml blood sample containing donor cellular nucleic acid and a plasma comprising cell-free nucleic acid, including a cell-free fetal nucleic acid, directly into an evacuated blood collection tube containing about 0.1 ml to about 0.3 ml protective agent that is formed from a solvent, and ingredients consisting of:

(i) about 300 g/l to about 700 g/l imidazolidinyl urea;

(ii) about 20 g/l to about 60 g/l glycine; and

(iii) about 60 g/l to about 100 g/l EDTA;

wherein the protective agent contacts and stabilizes storing the blood sample including the plasma for 1 to 14 days;

separating the plasma from the stored blood sample;

isolating the cell-free nucleic acid, including the cell-free fetal nucleic acid, from the plasma; and

amplifying the isolated fetal cell-free nucleic acid by at least 80-fold using whole genome amplification (WGA);

wherein the blood sample and the plasma is not frozen prior to the step of isolating.

15. A cell-free fetal nucleic acid based screening procedure utilizing the method of claim 1 .

16. The method of claim 1 , wherein the ingredients consist of the glycine, the imidazolidinyl urea, and the EDTA; and the protective agent is formed of only the solvent and the ingredients.

17. The method of claim 16 , wherein during storage, the collection tube contains only the drawn blood sample and the protective agent.

18. The method of claim 14 , wherein the protective agent is formed of only the solvent and the ingredients.

19. The method of claim 18 , wherein during storage, the collection tube contains only the drawn blood sample and the protective agent.

20. The method of claim 9 , wherein from 3.4% to 6.2% of the cell-free nucleic acid in the plasma is the cell-free fetal nucleic acid.