Single spin process for blood plasma separation and plasma composition including preservative

A method for identifying a characteristic of a target nucleic acid in a whole blood sample, comprising the steps of:

• a. positioning a composition comprising whole blood and a protective agent comprising at least one preservative agent within a centrifuge, wherein the preservative agent is selected from the group consisting of:
• diazolidinyl urea, imidazolidinyl urea, dimethoylol-5,5dimethylhydantoin, dimethylol urea, 2-bromo-2.-nitropropane-1,3-diol, oxazolidines, sodium hydroxymethyl glycinate, 5-hydroxymethoxymethyl-1-1aza-3,7-dioxabicyclo [3.3.0]octane, 5-hydroxymethyl- 1-1 aza-3,7dioxabicyclo[3.3.0]octane, 5-hydroxypoly[methyleneoxy]methyl-1-1 aza-3, 7dioxabicyclo[3.3.0]octane, quaternary adamantine and any combination thereof;
• b. centrifugating the composition at a speed of at least about 1000 g and below about 4500 g for at least about 5 minutes and less than about 20 minutes to isolate a plasma that includes the target nucleic acid for further analysis;
• c. isolating and testing the target nucleic acid obtained from step b to identify the characteristic of the target nucleic acid,
• wherein the method is free of any second centrifugating step, and wherein the target nucleic acid is cell-free plasma nucleic acid.