Ideally the test should be performed on plasma and we do not recommend the use of serum as nucleosome levels are much less stable in serum. However, if serum is the only thing that you have the test can be performed but the sample MUST be centrifuged within 20 min of the blood draw and the serum removed immediately. Serum levels are often slightly higher than plasma levels, so if your patient has a result in the moderate risk zone, then you may need to retest the patient using plasma to confirm the mild elevation in nucleosomes.