Urinary creatinine & specific gravity

Measurement of the urinary creatinine concentration was performed at the Mount Sinai Clinical Chemistry Laboratory using an Architect c16000 clinical chemistry analyzer combined with Architect system software (Abbott, IL, USA). The quality control procedure was performed using a liquid unassayed Multiqual control combined with Unity real-time software (Bio-Rad Laboratories, CA, USA). Concentration conversions were performed using Architect system software (Abbott). Urine specific gravity was measured using a J157HA+ automatic refractometer (Rudolph Research Analytical, NJ, USA).