Sensitivity and Specificity of Cystatin C in Detecting Early Renal Impairment in Hypertensive Pregnancies

Purpose: To determine the cutoff point of cystatin C for the detection of renal impairment in hypertensive pregnancies.
Methods: A cross-sectional study was conducted in an antenatal clinic and ward at Hospital Universiti Sains Malaysia, Kelantan, Malaysia from January 2009 until January 2010. Sixty four pregnant patients beginning at 2nd trimester, aged of 16 to 55 years and hypertensive, including gestational hypertension, chronic hypertension with superimposed preeclampsia, preeclampsia and unclassified hypertension, were included in the study. Consenting patients were required to provide 5 ml of blood and 24-h urine. Serum and reagent, N Latex cystatin C, were equilibrated at room temperature and measured by particle-enhanced nephelometric immunoassay (PENIA) using a BN II Dade Behring Nephelometer System
Results: The mean age of the patients was 37.06 ±4.32 (range: 24 to 46 years). A majority (64.1 %) of the patients were in the second trimester of pregnancy and delivered in the gestational period of 38 - 40 weeks (54.7 %). The number of patients in chronic kidney disease (CKD) stages I, II, III, IV and V were 25 (39.1 %), 18 (28.1 %), 18 (28.1 %), 2 (3.1 %) and 1 (1.6 %), respectively. The mean systolic blood pressure was 149.59 ± 18.79 mm Hg, and diastolic blood pressure 91.53 ± 10.33 mm Hg. The cutoff point in detecting renal impairment using cystatin C was > 0.74 with 84.6 % sensitivity and 86.7 % specificity for second trimester and > 0.81 with sensitivity of 76.9 % and specificity of 60.0 % in detecting renal impairment for third trimester.
Conclusion: The cutoff point in detecting renal impairment for second trimester is better than for third trimester since it maximizes the value of sensitivity and specificity.

Keywords
Cystatin C; Sensitivity; Specificity; Renal impairment; Hypertension; Pregnancy