Serum cystatin C for assessment of glomerular filtration rate in hypertensive disorders of pregnancy.

Background: Assessment of renal function is important in the evaluation of the pregnant hypertensive patient. The aim of this study was to evaluate the diagnostic utility of cystatin C as a marker of glomerular filtration rate in hypertensive disorders of pregnancy and to correlate this with serum creatinine and creatinine clearance.

Methods: For our study, 198 women who presented with hypertension during pregnancy were recruited at the antenatal clinic of King Edward VIII Hospital in Durban, South Africa, a tertiary referral centre. Exclusion criteria included women with eclampsia, urinary tract infection and chronic renal disease. Routine dipstick urinalysis (Bayer) was performed by midwives to classify patients suffering from the different forms of hypertensive disorders of pregnancy and venous blood samples for determination of serum cystatin C and serum creatinine were collected. The 24-hour urine creatinine clearance was used as the "gold standard" for evaluation of glomerular filtration rate due to concerns of radiation exposure to pregnant women with the use of radio nucleotide markers.

Results: The results of testing the 198 women, 72 of whom had preeclampsia, were analyzed. Serum cystatin C showed a significant correlation with creatinine clearance at the 0.01 level (2-tailed) with an r-value of -0.311. Serum creatinine showed a significant correlation with creatinine clearance at the 0.01 level (2-tailed) with an r-value of -0.486.

Conclusion: Serum cystatin C seems to reflect glomerular filtration rate reliably in hypertensive pregnant women and avoids the inaccuracy associated with the 24-hour urine collection, which is time consuming and subject to improper collection.