Evaluation of Serum Cystatin C as an Indicator of Glomerular Filtration Rate and its Correlations to other Biomarkers in Detection of Pre-eclampsia

Background : The Glomerular Filtration Rate (GFR) is the best indicator of renal function. Serum cystatin C has been introduced as an endogenous marker of GFR. However, there are conflicting reports regarding its use in pregnancy and pre-eclampsia. We aimed to assess the GFR changes in pre-eclampsia, evaluate the use of serum cystatin C as an indicator of GFR and to identify other biomarkers for detection of pre-eclampsia. Methods : This was a case-control study, conducted between December 2008 and December 2010, in Omdurman Maternity Hospital. The study group was 72 pre-eclamptic cases compared to 96 normal pregnant and 63 non-pregnant Sudanese women. Clinical and laboratory parameters including blood samples and 24-hour urine output were recorded. Total blood count, serum liver enzymes, renal function tests and serum cystatin C. Creatinine clearance and GFR were calculated. Results : Serum cystatin C level in the pre-eclamptic cases was significantly higher than the normal pregnant (P=0.000) and the non–pregnant participants (P=0.0001). Mean GFR of the pre-eclamptic cases was significantly lower than that of normal pregnant (P=0.0001) and the non-pregnant (P=0.0001). GFR of pre-eclamptic cases did not correlate with serum cystatin C nor with serum uric acid, but was negatively correlated with serum creatinine (r=-0.31, P=0.02). Serum cystatin C correlated with serum albumin (r=-0.41, P=0.0001), serum aspartate aminotransferase (r=0.26, P=0.03) and serum uric acid (r=0.60,P=0.0001) in the pre-eclamptic group. The diagnostic accuracy tests showed that serum cystatin C was a good detector of pre-eclampsia but not a reliable marker of GFR changes in pre-eclampsia. Conclusions : In pre-eclampsia, serum cystatin C level was significantly higher than in normal pregnancy. Serum cystatin C was superior to serum uric acid and serum creatinine in detection of pre-eclampsia but not a reliable indicator of GFR. Serum albumin and serum aspartate transferase can be used as additional biomarkers in pre-eclampsia. Keywords : Glomerular Filtration Rate, Pre-eclampsia, Serum Cystatin C, Serum Albumin, Serum Aspartate Aminotransferase