Blood urea nitrogen

Method

Serum urea nitrogen concentration by clinical assay, reported on the nitrogen scale.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

CAT:outcome/serum-creatinine is bundled with this on every 'renal panel' and both fall with benefit, but this analyte is strongly driven by protein intake, catabolic state and hydration independently of glomerular filtration — so it moves with diet in exactly the trials where creatinine does not, and treating the pair as one marker attributes a dietary effect to the kidney. The other near-miss is the same molecule on a different scale: serum urea is urea, this is urea nitrogen, and urea in mmol/L equals this value in mg/dL times 0.357. Two edges reporting the 'same' number on the two scales differ by a factor of 2.14 in mass terms and must never be pooled unconverted. Also distinct from serum uric acid, a purine catabolite under separate tubular control.