Measures of urine concentration in maternal urine screening for Down syndrome

Abstract

A study was carried out to assess eight methods of normalizing the level of urinary β‐core human chorionic gonadotropin (hCG) for variable urine concentration. We compared the standard approach—creatinine determination by the Jaffe method—with high performance liquid chromatography (HPLC) measurement of creatinine, osmolarity and optical density at five wavelengths. Urine samples were included from a total of 472 women with unaffected singleton pregnancies at 15 weeks' gestation. The median β‐core hCG value was determined for each decile group when the results were ranked in turn according to the different measures of urine concentration. Creatinine using the Jaffe method had a much stronger relationship with median β‐core hCG than the other measures. Linear regression across the decile groups gave an R2 value for Jaffe of 0·85 compared with HPLC of 0·53, osmolarity of 0·52, optical density at 405nm of 0·72, at 450nm of 0·57, at 490nm of 0·33, at 570nm of 0·34 and at 630nm of 0·33. We conclude that when screening with urinary β‐core hCG measuring creatinine appears to be an adequate method of allowing for variable urine concentration. Copyright © 1998 John Wiley & Sons, Ltd.

Direct and rapid mass spectral fingerprinting of maternal urine for the detection of Down syndrome pregnancy

“…Thus, urinary hCGβcf was considered to be potentially superior to serum hCG which was on average only increased about two-fold. However, not only did hCGβcf levels need to be corrected for gestational age, but adjustment had to be made for the dilutional effects of water intake and urination [ 15 ]. This meant that simple quantitated levels of hCGβcf per unit volume were so variable that performance as a single screening marker was not substantially greater, in terms of discriminatory power, than existing serum based analysis [ 16 - 18 ].…”

“…Indeed, since creatinine is influenced by body mass and increased metabolism, it was never an ideal correction factor for pregnant women. Although other corrections are possible they were neither robust nor sufficiently feasible to be practical [ 15 ].…”

Maternal Urine Screening for Down Syndrome: Past Studies and Future Perspectives

“…Another approach is to seek more specific and reproducible measures of urinary concentration. In one study, three methods of normalizing the level of hCGbcf for variable urine concentration were compared: high performance liquid chromatography measurement of creatinine, osmolarity and optical density [7]. But none were found to be an improvement over the Jaffe method.…”