If reference range is < 0.86 ng/mg for f2 isospostane/creatinine ratio urine test, what is normal reference range for just f2 isoprostane urine test ?

Oxidative stress: The F2-isoprostane/Cr ratio is the “gold standard” for measuring oxidative stress in people who have lifestyle risks due to poor diet or smoking, a family Hx of cardiovascular disease, or hyperlipidemia. ^ levels are seen in conditions with an incr risk of atherosclerosis and certain cancers. Urine values require creatinine in the analysis, range from 0.14 - 0.53 ng/mg w/ LC/MS, 1.02-1.30 w/ GC/MS