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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 452-457

Cystatin C and β2 microglobulin in preeclampsia: a prospective study


1 Departments of Obstetrics and Gynecology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Departments of Clinical Pathology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
3 Department of Obstetrics and Gynecology, Suez Insurance Hospital, Suez, Egypt

Date of Submission23-Mar-2019
Date of Decision17-Apr-2019
Date of Acceptance20-Apr-2019
Date of Web Publication27-Jun-2020

Correspondence Address:
Mohamed S. A. Soliman
Suez Insurance Hospital, Suez
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_135_19

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  Abstract 


Objective
To study the plasma levels of β-2-microglobulin (β2M) and cystatin C in patients with preeclampsia.
Background
The plasma level of cystatin C has been reported to have a better diagnostic performance for diagnosing preeclampsia.
Patients and methods
A prospective case–control study was carried out on 20 women diagnosed as having preeclampsia as well as 20 pregnant healthy. All patients attended the Obstetrics and Gynecology Department and outpatient clinic of Menoufia University Hospital, Menoufia Governorate, and Suez Insurance Hospital, Suez Governorate, during the study period from December 2016 to November 2017. Full history, routine, physical examination, and other investigations were taken.
Results
Mean antepartum and postpartum serum cystatin C, mean antepartum and postpartum serum β2M, albuminuria, and creatinine were increased significantly in preeclamptic patient group than the normal pregnancy group. The mean serum level of cystatin C before delivery was 1.78 ± 0.58 and 1.19 ± 0.32, which reduced significantly to 1.31 ± 0.49 and 0.91 ± 0.18 after delivery among preeclamptic patient and normotensive pregnancy groups, respectively. The mean serum level of β2M before delivery was 2.49 ± 0.56 and 1.92 ± 0.64, which reduced significantly to 1.98 ± 0.43 and 1.58 ± 0.49 after delivery among preeclamptic patients and normotensive pregnancy group, respectively.
Conclusion
Maternal serum cystatin C and β2M concentrations were significantly higher in preeclampsia compared with the normotensives. Cystatin C and β2M can be used as significant and independent predictive factors affecting the occurrence of preeclampsia.

Keywords: cystatin C, gestational age, preeclampsia, β2-microglobulin


How to cite this article:
Elsayed MA, Ellakwa HE, Hamza HA, Sonbol AA, Soliman MS. Cystatin C and β2 microglobulin in preeclampsia: a prospective study. Menoufia Med J 2020;33:452-7

How to cite this URL:
Elsayed MA, Ellakwa HE, Hamza HA, Sonbol AA, Soliman MS. Cystatin C and β2 microglobulin in preeclampsia: a prospective study. Menoufia Med J [serial online] 2020 [cited 2020 Oct 24];33:452-7. Available from: http://www.mmj.eg.net/text.asp?2020/33/2/452/287745




  Introduction Top


Preeclampsia is a pregnancy-specific disorder that affects 4% of pregnancies and is routinely diagnosed when a pregnant woman presents with increased blood pressure and proteinuria[1]. An increase in blood pressure can develop into renal dysfunction, and worsening of renal function will result in salt and water retention, which further complicate the hypertensive state. This vicious cycle can ultimately lead to severe preeclampsia, followed by poor obstetric outcome[2]. Preeclampsia is a common disorder of pregnancy and a major cause of maternal and fetal morbidity and mortality[3]. Today, most obstetricians recognize preeclampsia as a complex syndrome. The degrees of hypertension and proteinuria are poor prognostic factors for maternal and fetal outcome, and better diagnostic and prognostic markers are needed. Although numerous biochemical and hematologic markers have been studied for the prediction and monitoring of preeclampsia, there is no reliable marker for the disease[4]. Renal impairment characterized by proteinuria and decreasing glomerular filtration rate is a common feature in preeclampsia[5]. In the clinical setting, determination of serum urate and creatinine is a part of the workup in women with suspected preeclampsia. Serum urate has been suggested as the most sensitive indicator of preeclampsia available to clinicians[6]. In the past years, the circulating levels of the low-molecular-mass plasma proteins β2-microglobulin (β2M, 12 kDa) and cystatin C (13 kDa) have emerged as more sensitive markers of glomerular filtration than serum creatinine. In normal pregnancy, the maternal plasma levels of these proteins are elevated in the third trimester, secondary to a reduced renal filtration[4]. In preeclampsia, maternal plasma levels of cystatin C and β2M are increased[7], secondary to renal impairment[8]. The plasma level of cystatin C level has been reported to have a better diagnostic performance for diagnosing preeclampsia compared with the plasma levels of urate and creatinine, and it has been suggested as a complement to serum urate for diagnosing and monitoring preeclampsia in the clinical setting. The diagnostic performances of the plasma levels of β2M for diagnosing preeclampsia have not been studied previously[7]. This study was designed to study the plasma levels of β2M and cystatin C in preeclampsia.


  Patients and Methods Top


A prospective case–control study was carried out on 20 women diagnosed as having preeclampsia as well as 20 pregnant healthy. All patients attended the Obstetrics and Gynecology Department and outpatient clinic of Menoufia University Hospital, Menoufia Governorate, and Suez Insurance Hospital, Suez Governorate, during the study period from December 2016 to November 2017. All study patients were divided in two groups: group 1 included 20 women diagnosed as having preeclampsia, and group 2 included 20 normal pregnant who were free of any symptoms clinically and volunteered to participate in the study.

Ethical consideration

The study was approved by the ethical committee of Menoufia Faculty of Medicine, and an informed consent was obtained from all patients' guardian before the study was commenced.

Inclusion criteria were a singleton pregnancy at the third trimester of gestation, with preeclampsia diagnosed if blood pressure more than or equal to 140 mmHg systolic or more than or equal to 90 mmHg diastolic after the 32nd weeks of gestation, proteinuria defined as urinary excretion of 300 mg protein or higher in a 24-h urine specimen or more than 1+ on a urine dipstick (Combur Test) on at least two occasions 6 h apart at least and bilateral lower limb edema, and no associated other maternal diseases such as diabetes, hepatic, endocrinal, and renal disorders.

Multiple pregnancies and associated medical disorders with pregnancy were the exclusion criteria.

Method of sampling

The sample size was calculated using PASS 11.00 sample size calculation program and based on study finding carried out by Kristensen et al.[9]. The sample size included 20 patients with preeclampsia and 20 as controls to achieve 83% power to detect a difference of − 0.4 between serum cystatin C levels given the null hypothesis. Moreover, the same sample size was calculated based on area under the curve (AUC) of β2M, which will achieve 80% power.

All cases were subjected to the following:

Demographic data including age, weight, and height; obstetric history including parity, number of deliveries, and abortions, history of previous cesarean section and previous contraceptive methods; history of systemic diseases or current medications; history of previous pathologic gynecological lesions; and general and abdominal examination, which was performed with special concern to blood pressure measurement.

Ultrasonographic examinations

All patients were routinely scanned at admission to determine the fetal viability, fetal biometry, the presence of major fetal abnormalities, and asses the amount of liquor amnii.

Laboratory investigations

Urine sample was used for detection of proteinuria.

Blood sample: 8 ml of venous blood sample was collected from each individual during pregnancy at the third trimester and another sample at the third day after delivery, under aseptic condition by clean venipuncture without venous stasis. It was divided into four parts: 2.4 ml was added to an EDTA-contained sterile tube for the determination of complete blood count; 1.6 ml of blood was delivered into a tube containing 0.4 ml disodium citrate for prothrombin time; 2 ml was added to a sterile plain tube for assessment of renal and liver functions, where the blood was left to clot at 37°C and rapidly centrifuged at 3000 rpm for 10 min; and 2 ml were added to a sterile plain tube for assessment of cystatin C and β2M. The blood was left to clot at 37°C and rapidly centrifuged at 3000 rpm for 10 min and frozen at −80°C in aliquots and stored for later simultaneous analysis.

Complete blood count was measured by Sysmex xs 800i automated hematology analyzer (Sysmex Corporation, Chuo-ku, Kobe, Hyogo 651-0073, Japan). Liver and kidney function tests were measured on autoanalyzer AU 480 (AU Chemical Analyzer; Beckman Coulter, Atlanta, Georgia, USA). Alanine aminotransferase and aspartate aminotransferase were measured by quantitative kinetic method. Serum creatinine was measured by quantitative buffered kinetic Jaffe reaction.

Cystatin C measurement: two samples of cystatin C level were measured from maternal venous blood: the first was after 32 weeks of gestation and the second 3 days after labor. Cystatin C has been measured by using Nephstar system (Goldsite Diagnostics Inc., P.R. Shanghai, China). NEPHSTARTM Cystatin C (Cys C) Kit is used on NEPHSTARTM protein analysis system for quantitative determination of human Cystatin C (Cys C) in serum and plasma as an aid in diagnosis and treatment of renal diseases. The test principle is particle-enhanced immunonephelometry. This method involves measuring the light scattered by insoluble complexes formed by reaction between specific protein in samples and its respective antibody covalently coupled to latex particles, and the amount of scattered light is directly proportional to the concentration of the protein under condition that antiserum is in excess. The latex particles increase the size of complexes formed and thus the amount of light as well as the test sensitivity. Concentrations are automatically calculated by reference to a calibration curve stored in the instrument.

β2M measurement: two samples of β2M level were measured from maternal venous blood: the first was after 32 weeks of gestation and the second 3 days after labor. β2M has been measured by Mini Vidas System (bioMérieux SA, Marcy l'Etoile France). The assay principle combines a two-step enzyme immunoassay sandwich method with a final fluorescent detection. The Solid Phase Receptacle serves as the solid phase as well as the pipetting device for the assay. Reagents for the assay are ready to use and predispensed in the sealed reagent strips. All the assay steps are performed automatically by the instrument.

Statistical analysis

Results were tabulated and statistically analyzed by using a personal computer using Microsoft Excel 2016 and SPSS version 21 (SPSS Inc., Chicago, Illinois, USA). Statistical analysis was done using the following: descriptive, for example, percentage, mean, and SD, and analytical, which includes t test, paired t test, χ2 test, Mann–Whitney test, Fisher's exact test, and receiver operator characteristics curve. A value of P less than 0.05 was considered statistically significant.


  Results Top


The present study showed that the mean age was 31.8 ± 5.49 years in normotensive pregnancy group, whereas the mean age was 33.2 ± 5.17 years in preeclamptic patient group, with no statistical difference. There were statistically significant differences between preeclamptic patients and control groups regarding systolic blood pressure (SBP) (P < 0.001), diastolic blood pressure (DBP) (P < 0.001), and fat body weight (FBW) (P = 0.02). However, no significant differences were observed between preeclamptic patients and control groups regarding age, pulse, weight, gestational age (weeks), gravidity, parity, abortion, previous cesarean sections (P = 0.1), sex of the fetus (P = 0.11), and mode of delivery (P = 0.46) [Table 1].
Table 1: Comparison between the studied groups regarding patient characteristics

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Moreover, there were statistically significant differences between preeclamptic patients and control groups regarding mean antepartum and postpartum serum cystatin C, mean antepartum and postpartum serum β2M, albuminuria, and creatinine. All of the aforementioned parameters were increased significantly in preeclamptic patient group than the normal pregnancy group. On the contrary, there were no statistically significant differences between preeclamptic patient group and control group regarding uric acid, urea, alanine aminotransferase, aspartate aminotransferase, prothrombin time, partial thromboplastin time, international normalized ratio, hemoglobin, and platelets (×103) [Table 2].
Table 2: Comparison between the studied groups regarding laboratory investigations

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Furthermore, there were no statistically significant differences (P > 0.05) between mild and severe preeclamptic patients regarding antepartum and postpartum level of both cystatin C and β2M. The mean serum level of cystatin C before delivery was 1.78 ± 0.58 and 1.19 ± 0.32, which reduced significantly to 1.31 ± 0.49 and 0.91 ± 0.18 after delivery among preeclamptic patients and normotensive pregnancy group, respectively. The mean serum level of β2M before delivery was 2.49 ± 0.56 and 1.92 ± 0.64, which reduced significantly to 1.98 ± 0.43 and 1.58 ± 0.49 after delivery among preeclamptic patients and normotensive pregnancy group, respectively [Table 3].
Table 3: Comparison between the studied groups regarding antepartum and postpartum level of both cystatin C and β2-microglobulin

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Our results show that detection of preeclampsia by antepartum cystatin C level at cutoff point of 1.14 mg/l had a sensitivity of 80%, specificity of 50%, positive predictive value of 62%, and negative predictive value of 71.0%, with 65% overall accuracy. Regarding the detection of preeclampsia by antepartum β2M level at cutoff point of 2.01 mg/l, it had a sensitivity of 75%, specificity of 60%, positive predictive value of 68%, and negative predictive value of 72.0%, with 70% overall accuracy ([Table 4] and [Figure 1]).
Table 4: Antepartum cystatin C and β2-microglobulin receiver operator characteristics curve for preeclampsia detection

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Figure 1: Receiver operator characteristics (ROC) curve for antepartum cystatin C and β2M for detection of preeclampsia. β2M, β2-microglobulin.

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  Discussion Top


In the current study, there were statistically significant differences between preeclamptic patients and control groups regarding SBP (P < 0.001), DBP (P < 0.001), and FBW (P = 0.02). However, no significant differences were observed between preeclamptic patients and control groups regarding age, pulse, weight, gestational age (weeks), gravidity, parity, and abortions. Our results agree with Sharma et al.[10], who found that the mean age of 30 females with preeclampsia (cases) and 30 healthy pregnant females (controls) was similar. However, Farag et al.[11] reported that there were no significant differences between the two groups in terms of age or parity, but there was a significant difference in DBP (mmHg), SBP (mmHg), and the gestation at delivery as women who developed preeclamptic delivered early compared with normal pregnant women. Moreover, there were no significant differences in age and gestational age between the groups (P > 0.05) and a significant difference regarding SBP (mmHg) and DBP (mmHg). However, Franceschini et al.[12] found that women developing preeclampsia were slightly younger. In addition, cases had higher pre-pregnancy BMI than controls, and more often cases were physically inactive and current smokers. Cases also had lower mean gestational age at delivery. In addition, Kristensen et al.[9] found that the neonatal weight of patients with preeclampsia offspring was lower. The present study showed that incidence of previous cesarean section was increased among preeclampsia group compared with normal pregnancy with no statistically significant difference. These may be owing to small sample size of our study. Consequently, there were no statistically significant differences between preeclamptic patients and control groups regarding sex of the fetus and mode of delivery. The study conducted by Kristensen et al.[9] revealed that patients with preeclampsia delivered earlier than those with normal pregnancy. Moreover, Niraula et al.[13] found the same results. In the current study, there were no statistically significant differences between preeclamptic patients and control groups regarding uric acid, urea, liver function, international normalized ratio, hemoglobin, and platelets. In the study conducted by Kristensen et al.[9], it was revealed that serum uric acid levels decreased in the first trimester and then increased during the pregnancy, with the levels in the third trimester being significantly higher compared with the levels of nonpregnant women. Moreover, Novakov Mikic et al.[14] found that serum uric acid was found to be above reference range for control group in 37.5% of patients with preeclamptic, with significant differences between the mean values for the two groups[15],[16]. In addition, Amsterdam et al.[17] found significant differences between preeclamptic and controls. In the present study, there were no statistically significant differences between mild and severe preeclamptic patients regarding antepartum and postpartum levels of both cystatin C and β2M. The study conducted by Padma et al.[18] reported that cystatin C is a marker of kidney function that can be relied upon in assessing the severity of glomerular cell damage. Our results disagree with Gong et al.[19] and Wantania and Winarto[20], who found that patients with severe preeclampsia exhibited significantly higher serum cystatin C levels[21]. In the current study, mean serum level of cystatin C before delivery was 1.78 ± 0.58 and 1.19 ± 0.32, which reduced significantly to 1.31 ± 0.49 and 0.91 ± 0.18 after delivery among preeclamptic patients and normotensive pregnancy group, respectively. Our results agree with Guo et al.[22], who found that there was gradual decrease in the serum cystatin C after labor in preeclamptic patients. In the current study, detection of preeclampsia by antepartum cystatin C level at cutoff point of 1.14 mg/l had a sensitivity of 80%, specificity of 50%, positive predictive value of 62%, negative predictive value of 71.0%, with 65% overall accuracy. Regarding detection of preeclampsia by antepartum β2M level at cutoff point 2.01 mg/l, it had sensitivity of 75%, specificity of 60%, positive predictive value of 68%, and negative predictive value of 72.0%, with 70% overall accuracy. These results agree with Kristensen et al.[9], who reported that AUC of the cystatin C curve was 0.909 at cutoff point of 1.18, with cystatin C having 91.0% sensitivity and 77.0% specificity, and the AUC of the β2M curve was 0.89 at cutoff point of 2.25, with β2M having 80.0% sensitivity and 86.0% specificity. Another study conducted by Niraula et al.[13] revealed that the AUC of the cystatin C was 0.993, with cystatin C having diagnostic efficiency of sensitivity of 88.24% and specificity of 98.04%. In addition, Wattanavaekin et al.[23] found that by plotting a receiver operator characteristics curve, they found that a serum cystatin C concentration of higher than 1.48 mg/l has a sensitivity of 80% and specificity of 75% to detect preterm delivery in patients with preeclampsia.


  Conclusion Top


Maternal serum cystatin C and β2M concentrations were significantly higher in preeclampsia compared with the normotensives. Maternal serum level of cystatin C can be used as a predictor of preeclampsia, with cystatin C having 80.0% sensitivity, 50.0% specificity, 62% positive predictive value, and 71.0% negative predictive value, with 65% overall accuracy. Cystatin C and β2M can be used as significant and independent predictors affecting the occurrence of preeclampsia.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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