What exactly does the cortisol wand measure?Updated 3 hours ago

It is a fluorescence lateral flow immunoassay designed to measure urinary free cortisol, the same detection approach as the other Mira wands.

Free cortisol is the unbound, biologically active fraction of circulating cortisol. Most cortisol in blood is bound to cortisol-binding globulin and albumin and is inert while bound; only the free fraction, under 5% of the total, can enter tissues. Only free cortisol is filtered at the glomerulus, and most of what is filtered is reabsorbed or converted to cortisone by renal 11β-HSD2. The small remainder that reaches the urine unchanged is urinary free cortisol, under 1% of daily secretion. Its amount tracks the free cortisol concentration in plasma, so it serves as an index of active cortisol exposure over the collection interval. It rises disproportionately once binding globulin saturates, which is why it is less affected than total serum cortisol by estrogen-driven changes in binding protein.

The wand does not measure cortisone or cortisol metabolites. It therefore says nothing about total cortisol production, clearance, or 11β-HSD activity, which are what a DUTCH panel adds.