MEASURES OF URINE CONCENTRATION IN MATERNAL URINE SCREENING FOR DOWN-SYNDROME

A study was carried out to assess eight methods of normalizing the lev el of urinary beta-core human chorionic gonadotropin (hCG) for variabl e urine concentration. We compared the standard approach-creatinine de termination by the Jaffee method with high performance liquid chromato graphy (HPLC) measurement of creatinine, osmolarity and optical densit y at five wavelengths. Urine samples were included from a total of 472 women with unaffected singleton pregnancies at 15 weeks' gestation. T he median beta-core hCG value was determined for each decile group whe n the results were ranked in turn according to the different measures of urine concentration. Creatinine using the Jaffe method had a much s tronger relationship with median beta-core hCG than the other measures . Linear regression across the decile groups gave an R-2 value for Jaf fe of 0.85 compared with HPLC of 0.53, osmolarity of 0.52, optical den sity at 405 nm of 0.72, at 450 nm of 0.57, at 490 nm of 0.33, at 570 n m of 0.34 and at 630 nm of 0.33, We conclude that when screening with urinary beta-core hCG measuring creatinine appears to be an adequate m ethod of allowing for variable urine concentration. (C) 1998 John Wile y & Sons, Ltd.