Spot urine

protein (mg/dL)/creatinine (mg/dL) ≈ g/d of proteinuria (NEJM 1983;309:1543) unlike urine dipstick, will accurately measure myeloma light chains

reliable surrogate for 24-hr urine, esp. 1st morning void (JASN 2009;20:436); inaccurate if AKI depends on Cr production,

nb

underestimates if muscular, overestimates if cachectic