The effects of diaper brands, urine volume, and time on specific gravity measurement

Nurses use urine specific gravity to assess fluid volume status in pediatric patients. Specific gravity of five leading brands of disposable diapers was measured to determine the effects of diaper brand, urine volume, time elapsed, and method of specific gravity measurement comparing the two methods of refractometry and N-Multistix SG (Ames Division, Miles Inc., Elkhart, IN). Immediately after a baby voided 20 mL of urine into any disposable diaper, the specific gravity by refractometer accurately compared with the control standard. Measurement accuracy by N-Multistix SG was only assured if Pampers (Procter & Gamble, Cincinnati, OH) were used. However, both methods were inaccurate at 4 hours with 20 mL of urine. Immediately after a baby voided 40 mL of urine into any disposable diaper, both methods were accurate when compared with the control. At 4 hours, only Pampers and Chux (Procter & Gamble, Cincinnati, OH) were accurate by refractometry, and Pampers alone was accurate by N-Multistix SG.