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Cystatin‐C and beta trace protein as markers of renal function in pregnancy
Author(s) -
Akbari Ayub,
Lepage Nathalie,
Keely Erin,
Clark Heather D.,
Jaffey James,
MacKin Martin,
Filler Guido
Publication year - 2005
Publication title -
bjog: an international journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.157
H-Index - 164
eISSN - 1471-0528
pISSN - 1470-0328
DOI - 10.1111/j.1471-0528.2004.00492.x
Subject(s) - creatinine , renal function , medicine , cystatin c , pregnancy , urology , prospective cohort study , gestation , population , endocrinology , biology , genetics , environmental health
Objective To assess the validity of Cystatin‐C (Cys‐C) and beta trace protein (BTP) as clinical markers of glomerular filtration rate (GFR) in pregnant women. Design Prospective cross sectional study. Setting Obstetric unit of a tertiary care hospital. Population One hundred and thirty‐seven normal pregnant women and 13 women postpartum. Methods Twenty‐four hour creatinine clearance (CrCl), serum creatinine, Cys‐C and BTP concentrations were measured on normal pregnant women in the first trimester ( n = 5), second trimester ( n = 68) and third trimester ( n = 64) and in 13 women postpartum. Data are given as median (2.5th centile, 97.5th centile). Main outcome measures Serum concentrations of Cys‐C and BTP compared with creatinine clearance and serum creatinine. Results The median serum creatinine throughout gestation was 53 μmol/L (39, 71), and median CrCl was 143 mL/minute (91 to 216). Postpartum, creatinine rose to 74 μmol/L (58, 86) and CrCl decreased to 104 mL/minute (71, 159). For Cys‐C, the median concentration was 0.70 mg/L (0.46, 1.32), and 0.54 mg/L (0.36, 0.96) for BTP. Comparing the second and third trimesters, there was no significant difference between CrCl (median 145 vs 141 mL/minute) and BTP concentrations (median 0.51 vs 0.55 mg/L), while median Cys‐C was significantly higher in the third trimester (0.61 vs 0.88 mg/L; P < 0.001). Unlike creatinine and BTP, Cys‐C levels decreased to 0.72 mg/L (0.57, 0.95) postpartum. The only significant relationship of either of these markers to the standard used for GFR was between Cys‐C and CrCl in the third trimester, and the correlation was weak ( r = 0.27 for 1/Cys‐C vs CrCl). Conclusion These data demonstrate that despite claims to the contrary, Cys‐C is a poor marker of GFR during pregnancy. Similarly, BTP shows little promise.