NPB and nasopharyngeal carcinoma: Using our oxidation/derivatisation method the free acids are preferentially observed and, in the absence of an authentic standard, 3β,5α,6β,24-tetraHCa was presumptively identified by LC retention time, exact mass and MS3 spectrum in plasma samples from NPC (0.5–2.5 ng/mL), NPB (2.5–4 ng/mL) and LALD (0.5–4.5 ng/mL, see Supplemental Figure S5Q in Ref.