Cystatin-C and beta trace protein as markers of renal function in pregnancy

Effects of intrauterine growth restriction during late pregnancy on the ovine fetal renal function and antioxidant capacity

This study investigated the effects of intrauterine growth restriction during late pregnancy on the ovine fetal renal function and renal antioxidant capacity. Eighteen ewes pregnant were randomly divided into control group (CG, ad libitum, 0.67 MJ ME·BW^-0.75 ·day^-1 , n = 6), restricted group 1 (RG1, 0.18 MJ ME·BW^-0.75 ·day^-1 , n = 6), and restricted group 2 (RG2, 0.33 MJ ME·BW^-0.75 ·day^-1 , n = 6). At 140 days, the fetal blood, allantoic fluid and kidney tissue were collected to determinate fetal renal function and renal antioxidant capacity. The results showed that the fetal weight, kidney weight, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), aquaporin-2 (AQP-2) and aquaporin-3 (AQP-3), and total antioxidant capacity (T-AOC) in RG1 group were decreased compared with the CG (P < 0.05), but the contents of β2-Microglobulin (β 2-MG), cystatin C (Cys-C), filtered sodium excretion fraction (FENa), malondialdehyde (MDA), and hydroxyl radical (OH) in RG1 group were increased (P < 0.05). The impaired ovine fetal renal growth, antioxidant imbalance and dysfunction of glomerulus ultrafiltration, and the renal tubules reabsorption were induced by maternal malnutrition during late pregnancy.

Cord blood gas results of pregnancies complicated by preeclampsia and the relationship of these results with the amount of proteinuria

AIM

To evaluate whether there is a statistically significant difference between the cord blood gas parameters of pregnancies complicated with preeclampsia and uncomplicated pregnancies and to show whether the amount of proteinuria affects fetal cord blood gas parameters in pregnancies complicated with preeclampsia.

METHODS

The study was designed retrospectively. Between 2016 and 2019, the neonatal results and cord blood gas results of 109 pregnant women who were diagnosed with preeclampsia and 75 nonpreeclamptic randomly selected pregnant women were compared. The preeclampsia group was divided into groups according to amount of proteinuria. SPSS 21.0 statistics program was used, and comparative analysis was carried out.

RESULTS

The data of the 109 preeclampsia cases and 75 control groups included in the study were compared, and there was no statistical difference between the fetal cord blood gas parameters between the groups (p > 0.05). The median first and fifth minute Apgar scores were found significantly lower in the preeclampsia group compared to the control group (6, 8 and 8, 9, respectively; p < 0.001). Also, the amount of proteinuria does not alter cord blood gas parameters (p > 0.05).

CONCLUSION

Preeclampsia poses a risk for the neonatal period as it reduces the neonatal Apgar scores due to the chronic hypoxic process it creates. However, it was observed that the amount of proteinuria, which is one of the diagnostic criteria, did not affect neonatal results on Apgar scores or fetal cord blood gas parameters.

Pregnancy-induced changes in serum concentrations of perfluoroalkyl substances and the influence of kidney function

BACKGROUND

Epidemiological associations between maternal concentrations of perfluoroalkyl substances (PFAS) and birth weight are inconsistent. There is concern that studies based on samples collected in late pregnancy may be confounded by kidney function but studies of the relation between pregnancy-induced changes in PFAS and kidney function are lacking. Our aims were to investigate changes in serum concentrations of perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) from early to late pregnancy and to explore relations to changes in glomerular filtration rate (GFR) and glomerular pore size.

METHODS

We conducted the study in a cohort of 73 pregnancies of normal-weight Swedish women without gestational diabetes and preeclampsia, enrolled 2009-2014. Blood was collected in median weeks 11 and 36, respectively, and analysed PFAS using liquid chromatography-tandem-mass-spectrometry. We estimated GFR based on creatinine and cystatin C and used the ratio eGFR_{cystatin C}/eGFR_creatinine to indicate glomerular pore size. We used Wilcoxon signed-rank test to compare early and late measures and partial Spearman rank correlations to explore relations between changes in PFAS and kidney function.

RESULTS

Median concentrations of PFNA, PFOA and PFOS decreased by 15-21% but changes were uncorrelated to changes in kidney function (partial R = - 0.06-0.11). The observed increase in median PFHxS concentration of 69% was likely an artefact of systematic measurement error caused by coeluting endogenous inferences.

CONCLUSIONS

Serum concentrations of PFNA, PFOA and PFOS decrease during pregnancy but the magnitudes of change are unrelated to parallel changes in eGFR and glomerular pore size, suggesting that changes in these indicators of kidney function are not important confounders in studies of PFAS and birth weight in pregnancies without gestational diabetes and preeclampsia.

The Value of a Cystatin C-based Estimated Glomerular Filtration Rate for Cardiovascular Assessment in a General Japanese Population: Results From the Iwate Tohoku Medical Megabank Project

BACKGROUND

Epidemiological studies have shown that high circulating cystatin C is associated with a risk of cardiovascular disease (CVD) independent of creatinine-based renal function measurements. The present study investigated the comparison between the cystatin C-based estimated glomerular filtration rate (GFRcys) and creatinine-based GFR (GFRcr) to determine whether these measurements are associated with CV biomarkers and elevated CVD risk in a general Japanese population.

METHODS

The Iwate Tohoku Medical Megabank Organization pooled individual participant data from a general population-based cohort study in Iwate prefecture (n = 29,375). Chronic kidney disease (CKD) was estimated using the GFRcys, GFRcr and the urine albumin-to-creatinine ratio (UACR).

RESULTS

The prevalence of CKD in the participants was found to be higher based on the GFRcr than the GFRcys. Multiple variable analyses after adjusting for baseline characteristics showed that high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were associated with the GFRcys. The area under the receiver operating characteristic (AUROC) curve for identifying individuals with a high Suita score was higher for the GFRcys (AUROC = 0.68) than it was for the GFRcr (AUROC = 0.64, P < 0.001). The GFRcys provided reclassification improvement for the CVD risk prediction model by the GFRcr (net reclassification improvement = 0.341; integrated discrimination improvement = 0.018, respectively, P < 0.001).

CONCLUSIONS

The GFRcys is more closely associated with CV biomarkers, including hs-cTnT and NT-proBNP levels, and a high Suita score than the GFRcr, and it provides additional value in the assessment of CVD risk using GFRcr.

Serum Cystatin C Levels in Twin Pregnancy versus Singleton Pregnancy

OBJECTIVE

To explore whether there was an increased secretion of cystatin C (Cys C) in twin pregnancy.

METHODS

Patients with a total of 281 singleton pregnancies (including 38 patients with preeclampsia) and 72 twin pregnancies, as well as 42 patients who were not pregnant, were included in this study. We tested levels of serum Cys C, creatinine, and uric acid, along with the estimated glomerular filtration rate (eGFR), in different groups.

RESULTS

The levels of serum Cys C in all 3 trimesters for women with twin pregnancy were much higher than those in the corresponding trimesters for women with singleton pregnancy. However, we observed little change in eGFR in the corresponding trimesters. Cys C/eGFR in the second and third trimester of twin pregnancy increased, compared with the corresponding trimesters of women with singleton pregnancy. Levels of serum Cys C were higher in the third trimester in women with twin pregnancy than that in patients with preeclampsia. Also, Cys C/eGFR in the third trimester of twin pregnancy was close to the level observed in patients with preeclampsia.

CONCLUSIONS

Increased secretion of Cys C could contribute to the elevated serum Cys C levels that we observed in twin pregnancy.

Educational review: measurement of GFR in special populations

IMPORTANCE

Changes in kidney function are typically followed by the sequential estimation of glomerular filtration rate (eGFR). Formulae for eGFR work well on a population basis, but there are well-known conditions where they do not work.

OBJECTIVE

The purpose of this review is to summarize the existing literature on special populations in the pediatric age range and provide recommendations on how to estimate GFR in these populations.

FINDINGS

The reliability of creatinine depends on muscle mass, while cystatin C (not widely available) is limited by inflammation and changes in protein catabolism. Various dietary factors can alter eGFR. Renal function in neonates changes drastically every day, and there are currently no satisfactory reference intervals for routine pediatric use. Gender effects and conditions such as wasting disease and obesity require alternative ways to obtain eGFR. In oncology patients, chemotherapy may negatively affect renal function, and nuclear GFR measurements may be necessary. For body builders, high muscle mass may lead to underestimation of eGFR using creatinine.

CONCLUSIONS AND RELEVANCE

Clinicians should be aware of special populations that may yield misleading eGFRs with conventional creatinine-based formulae, and that the alternative methods may be more appropriate for some populations.

Serum Creatinine in Pregnancy: A Systematic Review

Introduction

Standard assessment of renal function in pregnancy is by measurement of serum creatinine concentration yet normal gestational ranges have not been established. The aim of this systematic review was to define the difference in serum creatinine in a healthy pregnancy compared with concentrations in nonpregnant women to facilitate identification of abnormal kidney function in pregnancy.

Methods

Medline, PubMed, Embase, Web of Science, theses, key obstetric texts, and conference proceedings were searched to July 2017. Eligible studies included quantification of serum creatinine concentration in a pregnant cohort, with either a reported local laboratory reference range or matched quantification in a nonpregnant cohort. The outcomes of interest were the mean and upper reference limits for creatinine in pregnancy, measured as a ratio of pregnant:nonpregnant values. Study heterogeneity was examined by meta-regression analysis.

Results

Forty-nine studies were identified. Data synthesis included 4421 serum creatinine values in pregnancy, weighted according to cohort size. Mean values for serum creatinine in pregnancy were 84%, 77%, and 80% of nonpregnant mean values during the first, second, and third trimesters, respectively. The 97.5th centile (upper limit of the 95% reference range) for serum creatinine in pregnancy was 85%, 80%, and 86% of the nonpregnant upper limit in sequential trimesters.

Conclusion

Based on a nonpregnant reference interval of 45–90 μmol/l (0.51–1.02 mg/dl), a serum creatinine of >77 μmol/l (0.87 mg/dl) should be considered outside the normal range for pregnancy. Future work can use this value to explore correlation of adverse pregnancy outcomes with serum creatinine concentration. PROSPERO registration: CRD42017068446

Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy

BACKGROUND

In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues.

OBJECTIVES

The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues.

METHODS

A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility.

RESULTS

The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions.

CONCLUSION

The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.

Serum Beta-Trace Protein as a Novel Predictor of Pregnancy-Induced Hypertension

Beta-trace protein (BTP) has emerged as a novel biomarker of cardiovascular risk. However, the level of circulating BTP in pregnancy-induced hypertension (PIH) is still unknown. The aim of this study was to determine the concentration of serum BTP in healthy pregnant women and patients with PIH. No significant difference was found in the serum concentration of BTP in patients with a normal pregnancy. In contrast, serum BTP levels in women with PIH (n=46) were significantly higher than those in women with normal pregnancy (n=57). Receiver operating characteristic analysis revealed that using a serum BTP value of 321.3 ng/mL as a cutoff produced a sensitivity of 91.3% and a specificity of 89.5%. Taken together, these findings suggest that a higher serum BTP concentration in PIH patients compared with those with normal pregnancy and serum BTP might be a novel biomarker in the diagnosis of PIH.

Assessment of glomerular filtration rate in the neonate: is creatinine the best tool?

PURPOSE OF REVIEW

This article answers the question of whether creatinine is the best biomarker for monitoring neonatal glomerular filtration rate (GFR) in view of recent advances in measuring neonatal renal function.

RECENT FINDINGS

We rely largely on serum creatinine for the estimation of GFR in the newborn, even though creatinine is freely exchanged through the placenta. During the first few days of life, the serum creatinine reflects maternal renal function or the maternal creatinine. Back filtration of creatinine in preterm newborns is also a serious limitation. This review summarizes current knowledge on the prenatal and postnatal handling of creatinine as well as that of other, more novel biomarkers of GFR, such as cystatin C (CysC) and β-trace protein (BTP). Only small amounts of CysC cross the placenta, whereas BTP does not cross the placenta at all. However, BTP measurements are not widely available. Recent studies on renal volumetry are also discussed.

SUMMARY

Currently, CysC may be the most suitable marker of neonatal renal function, but its availability is still limited, it is more costly, and the best method of reporting acute kidney injury and neonatal estimated GFR remains to be established.

An analysis of the differences between early and late preeclampsia with severe hypertension

Preeclampsia is clinically divided into early onset and late onset preeclampsia based on the gestational age at delivery. Although the diagnostic criteria are the same in each subgroup of preeclampsia, it has been suggested that the maternal and perinatal mortalities of early onset and late onset preeclampsia are different. However, studies that compare clinical parameters or laboratory biomarkers between early onset and late onset preeclampsia are limited. Data on 177 women with early or late preeclampsia with severe hypertension were collected from a University Teaching Hospital from January 2010 to January 2011 and analysed. Data included all the clinical parameters and laboratory biomarkers of liver and renal function. 63 women and 114 women were diagnosed with early and late preeclampsia with severe hypertension, respectively. There was no difference in the maternal age and the incidence of clinical symptoms including edema, vision disturbance, severe headache and stillbirth between two groups. There was a decrease in alkaline phosphatase levels in early preeclampsia with severe hypertension but other markers of liver function were not altered. However, renal function including blood urea nitrogen, creatinine and uric acid were significantly higher in early preeclampsia with severe hypertension. Umbilical artery systolic velocity/diastolic velocity ratio was significantly higher in early preeclampsia with severe hypertension. Our data demonstrates that the laboratory biomarkers of renal function differ between early and late preeclampsia with severe hypertension. The severity of renal dysfunction correlated with the time of delivery in preeclampsia with severe hypertension.

Update on Estimation of Kidney Function in Diabetic Kidney Disease

The American Diabetes Association recommends annual assessment of glomerular filtration rate (GFR) to screen for diabetic nephropathy. GFR is measured indirectly using markers that, ideally, are eliminated only by glomerular filtration. Measured GFR, although the gold standard, remains cumbersome and expensive. GFR is therefore routinely estimated using creatinine and/or cystatin C and clinical variables. In pediatrics, the Schwartz creatinine-based equation is most frequently used even though combined creatinine and cystatin C-based equations demonstrate stronger agreement with measured GFR. In adults, the CKD Epidemiology Collaboration (CKD-EPI) equations with creatinine and/or cystatin C are the most accurate and precise estimating equations. Despite recent advances, current estimates of GFR lack precision and accuracy before chronic kidney disease stage 3 (GFR < 60 mL/min/1.73 m(2)). There is therefore an urgent need to improve the methods for estimating and measuring GFR. In this review, we examine the current literature and data addressing measurement and estimation of GFR in diabetes.

The Importance of Accurately Assessing Renal Function in the Neonate and Infant

Measuring renal function in neonates and small infants is important to ensure that drugs are safely dosed and to detect acute kidney injuries early on. Serum creatinine (Cr) remains the most widely used marker, but its shortcomings are particularly important in neonates. For example, neonatal Cr largely depends on maternal renal function for at least the first 72 h of life. Novel approaches for assessing neonatal renal function include cystatin C and beta-trace protein. Another way to assess renal function is to measure renal volume by ultrasound. Although this approach may assess neonatal nephron endowment, it is insensitive to the postnatal adaptation of renal function in term and preterm neonates. The purpose of this review is to summarize what is known about measuring renal function in term and preterm newborns, and to summarize existing knowledge gaps, including a description of steps to take to close these gaps.

Beta-trace protein as a marker of GFR--history, indications, and future research

OBJECTIVES

Recent findings suggest that beta-trace protein (BTP), a small molecular weight protein, is at least equal if not superior to serum creatinine as a marker of glomerular filtration rate (GFR), particularly since it is independent from height, gender, age, and muscle mass. The authors sought to summarize knowledge on BTP and its use as a marker of GFR using the most recent literature available.

DESIGN AND METHODS

The authors compiled key articles and all relevant recent literature on this topic. Physical and chemical features of the molecule are described, as well as factors that may affect its expression. The use of BTP in estimating GFR as a whole and in specific patient groups, including pregnant women, neonates and infants, children and adolescents, and patients who have undergone renal transplantation is discussed. The use of BTP as a marker for cardiovascular risk factors is also briefly addressed.

RESULTS

Although its performance in the general population is marginally inferior to cystatin C, studies have suggested that it may be superior in accurately estimating GFR in select patient groups such as pregnant women and neonates.

CONCLUSIONS

This novel marker shows promise, but further research is required to clarify findings from available data.

Methods of assessing renal function

Accurate assessment of renal function is critical for appropriate drug dosing of renally excreted compounds. Glomerular filtration rate (GFR) is considered the best marker of kidney function. Inulin clearance forms the gold standard for measuring GFR, both in adults and in children. The method is invasive, cumbersome, and smaller children require urinary catheterization for accurate timed urine collections. Nuclear medicine methods replaced inulin clearance in the 1970s after (51)Cr EDTA clearance was introduced. Inulin has no plasma protein binding, whereas all commonly used radioisotopes have a small amount of plasma protein binding that leads to lower values. Only iohexol does not have significant plasma protein binding. The underestimation due to plasma protein binding is partially offset by overestimation due to the use of non-compartmental pharmacokinetic modeling of the plasma disappearance of the radioisotope. The problem could be overcome with a urinary nuclear medicine clearance method, but these have not been validated in children. Endogenous markers of GFR include serum creatinine and low molecular weight proteins such as cystatin C and beta-trace protein. Of these, estimation of GFR using cystatin C appears to be the most promising, although its accuracy in pregnancy and in the neonatal period may be limited.

Plasma cystatin-C and risk of developing gestational diabetes mellitus

AIMS

Cystatin-C, a low molecular weight protein, is effectively applied to evaluate the risk of developing renal insufficiency, cardiovascular disorders, neural defects, and inflammatory states. However, the role of this biomarker to monitor different pregnancy-related complications remains controversial.

MATERIALS AND METHODS

In the present study, we compared serum cystatin-C concentration between pregnant women with gestational diabetes mellitus (GDM) and healthy pregnant women to assess value of this biomarker to predict presence of GDM in these women. The study consisted of 60 consecutive pregnant women (30 women suffered GDM and 30 healthy pregnant women) enrolled in Afzalipour hospital in Kerman, Iran in 2012. Fasting blood sample was collected to perform measurements on plasma glucose, lipids, serum creatinine, and C-cystatin. Serum cystatin-C level was quantified using ELISA techniques.

RESULTS

Unadjusted comparison of cystatin-C level between the two study group showed no significant discrepancy between them so that the level of this biomarker in GDM group was 593.00±204.81 mg/L and in healthy group was 531.67±87.52 mg/L (P=0.137); while in multivariable linear model with the presence of associated variables, GDM was a main determinant for increased level of cystatin-C (standardized beta of 0.355, P-value of 0.014).

CONCLUSION

Gestational age was also identified to be another indicator of elevated cystatin-C. In final, our study showed that cystatin-C can be a reliable, useful and promising marker of GDM appearance in pregnant women.

Correlation of cystatin-C with glomerular filtration rate by inulin clearance in pregnancy

OBJECTIVE

To test utility of cystatin-C as a marker of glomerular filtration rate during pregnancy, we performed serial correlations with inulin clearance during pregnancy and postpartum.

METHODS

Twelve subjects received inulin infusions and serum cystatin-C at three time points. Pearson's correlation coefficient was calculated.

RESULTS

Cystatin-C levels ranged 0.66-1.48 mg/L during pregnancy, and 0.72-1.26 mg/L postpartum. Inulin clearance ranged 130-188 mL/min during pregnancy, and 110-167 mL/min postpartum. Cystatin-C did not correlate with inulin clearance at any time point.

CONCLUSION

Serum cystatin-C did not correlate with inulin clearance during pregnancy or postpartum.

Management of renal disease in pregnancy

Although renal disease in pregnancy is uncommon, it poses considerable risk to maternal and fetal health. This article discusses renal physiology and assessment of renal function in pregnancy and the effect of pregnancy on renal disease in patients with diabetes, lupus, chronic glomerulonephritis, polycystic kidney disease, and chronic pyelonephritis. Renal diseases occasionally present for the first time in pregnancy, and diagnoses of glomerulonephritis, acute tubular necrosis, hemolytic uremic syndrome, and acute fatty liver of pregnancy are described. Finally, therapy of end-stage renal disease in pregnancy, dialysis, and renal transplantation are reviewed.

Serum and urinary markers of early impairment of GFR in chronic kidney disease patients: diagnostic accuracy of urinary β-trace protein

The screening for chronic kidney diseases (CKD) patients with impaired GFR needs the measurement of serum creatinine (SCr) or cystatin C (SCys). GFR can also be predicted from SCr or SCys with different formulas. The aim of this study, performed in a group of CKD patients with different levels of GFR, was to evaluate the possibility to select the patients with a GFR <90 ml·min(-1)·1.73 m(-2) by means of serum levels and urinary excretion of different low-molecular-weight proteins (LMWP), cystatin C (Cys), β2-microglobulin (β2M), retinol-binding protein (RBP), β-trace protein (BTP), and derived prediction equations for GFR. In the 295 CKD patients (137 women), at all stages of GFR impairment a very high correlation was found between GFR ((99m)Tc-DTPA) and serum Cr, Cys, β2M, and BTP. All these serum markers showed a similar accuracy as indicators of different GFR impairments. RBP had the lowest correlation with GFR and was also significantly less accurate. The different prediction formulas derived from gender, anthropometric data and SCr or S-LMWP had a diagnostic accuracy similar to that of serum Cr, Cys, β2M, and BTP. Urinary albumin was inadequate as an indicator of any level of GFR impairment. Urinary excretion of Cys and β2M increased significantly only in patients with a GFR <30 ml·min(-1)·1.73 m(-2), while urinary BTP increased already at GFR <90 ml·min(-1)·1.73 m(-2). In this selected group of CKD patients, the positive predictive value of urinary BTP for a GFR <90 ml·min(-1)·1.73 m(-2) was 85%, indicating that, in CKD patients, a urine-based test can predict a slight GFR impairment.

Development of a beta-trace protein based formula for estimation of glomerular filtration rate

Beta-trace protein (BTP) is a novel marker of glomerular filtration rate (GFR). To date, no pediatric formula for calculating GFR based on BTP has been developed. We measured GFR, serum creatinine and BTP in 387 children who underwent 474 (99m)Tc-diethylene triamine pentaacetic acid renal scans. A BTP-based formula for estimating GFR was derived using stepwise linear regression analysis. A separate control group of 116 measurements in 99 children was used to validate the novel formula. A formula was also developed for each gender. The novel formula is: [formula: see text]. The Spearman rank correlation coefficient between the BTP-derived GFR estimate and the measured GFR was 0.80 [95% confidence interval (CI) 0.76-0.83], which is substantially better than that derived with the Schwartz formula (r = 0.70, 95% CI 0.65-0.74). The Bland-Altman analysis revealed a mean bias of 1.21% [standard deviation (SD) 28%] in the formula development dataset, which was virtually identical to the 1.03% mean bias (29.5% SD) in the validation group and no different from the Schwartz formula bias. The percentage of values within 10% (33.0 vs. 28.3%) and 30% deviation (76.8 vs. 72.6%) were better for BTP-based formula than for the Schwartz formula. Separate formulas according to gender did not perform better than that for the pediatric population. This BTP-based formula was found to estimate GFR with reasonable precision and provided improved accuracy over the Schwartz GFR formula.

A comparison of prediction equations for estimating glomerular filtration rate in pregnancy

OBJECTIVE

To compare existing glomerular filtration rate (GFR) prediction equations with the gold standard, inulin clearance, in pregnancy.

METHODS

Five equations were assessed for precision, bias, and accuracy in prediction of true GFR, measured by inulin clearance in 12 healthy, pregnant women during the second (T2) and third (T3) trimesters and in postpartum (PP).

RESULTS

Precision was greatest with 24-hour creatinine clearance estimation of GFR (R(2) = 13% (T2), R(2) = 26% (T3)). Other than 100/SCr, all equations underestimated true GFR. 30% accuracy was greatest in 100/SCr (83% (T2), 92% (T3)).

CONCLUSIONS

Current GFR prediction formulae do not appear to be sufficient for estimating GFR in the gravid state.

Serum cystatin is not a marker of glomerular filtration rate in pregnancy

The role of cystatin C (Cys-C) as a marker of glomerular filtration rate (GFR) in pregnancy is undetermined. Measurements of Cys-C and creatinine (Cr) were taken at 14-17(+6), 18-23(+6), 27-31(+6) weeks' gestation, at delivery and 2-6 weeks postpartum in a prospective observational study of 27 women. There was no difference between Cys-C levels in early and late second trimester, but they were significantly higher in early third trimester (P < 0.001) than second trimester, despite no concurrent increase in Cr. Cys-C was also significantly higher at delivery than at all other times in pregnancy (P < 0.001) and fell to postpartum values higher than second trimester measurements (P < 0.01), but lower than delivery (P<0.001). In conclusion, changes in Cys-C may be influenced by pregnancy-related changes in glomerular filtration and therefore we would advise against their use as a marker of GFR in pregnancy.

Temporal changes of the plasma levels of cystatin C, β‐trace protein, β2‐microglobulin, urate and creatinine during pregnancy indicate continuous alterations in the renal filtration process

OBJECTIVE

To determine the plasma levels of the renal functional markers creatinine, urate, cystatin C, beta2-microglobulin and beta-trace protein in samples from the first, second, early third and late third trimesters of 398 healthy women with uncomplicated singleton pregnancies.

MATERIAL AND METHODS

Plasma samples from 58 healthy non-pregnant women served as controls. The creatinine levels were significantly lower at all time-points in pregnancy, whereas the urate levels were lower during the first and second trimesters but increased in the late third trimester. The cystatin C, beta2-microglobulin and beta-trace protein levels displayed similar changes with increased levels in the third trimester but unaltered levels during the first and second trimesters.

RESULTS

The results indicate an increased filtration of low-molecular weight molecules during pregnancy, particularly during the first and second trimesters, whereas filtration of 10-30 kDa molecules is decreased in the third but unaltered in the first and second trimesters. The levels of albumin and alph2-macroglobulin were measured in the same samples.

CONCLUSIONS

The albumin levels decreased in the second and third trimesters, whereas the levels of chi2-macroglobulin were unchanged, which is compatible with a virtually unaltered transfer of chi2-macroglobulin between the intra- and extravascular space during pregnancy and a significantly increased extravascular fraction of albumin.

Novel approaches to assessing renal function in cirrhotic liver disease

Renal dysfunction is common in patients with end-stage liver disease. Etiological factors include conditions as diverse as acute tubular necrosis, immunoglobulin A nephropathy and hepatorenal syndrome. Current standard tests of renal function, such as measurement of serum urea and creatinine levels, are inaccurate as the synthesis of these markers is affected by the native liver pathology. This article reviews novel markers of renal function and their potential use in patients with liver disease.

Obstetric considerations in the management of pregnancy in kidney transplant recipients

Kidney transplant improves reproductive function; planning for pregnancy is crucial. Prenatal management must address potential fetal complications: preterm delivery, intrauterine growth restriction, low birth weight; as well as maternal: hypertension, preeclampsia, gestational diabetes, acute rejection or graft loss. The latter depends upon timing after transplant, prepregnancy kidney function, and continuation of immunosuppressive agents at appropriate levels. Graft function is not adversely affected if preconception kidney function was normal. Acute rejection, 9%-14%, must be immediately addressed, with kidney biopsy if necessary. Blood pressure should be meticulously managed; serious morbidity results from poor control. Blood pressures >130/80 mmHg require acceptable antihypertensives: beta-blockers, alpha-methyldopa, hydralazine, and calcium channel blockers. Preeclampsia requires seizure prophylaxis with magnesium sulfate, with expeditious delivery. Screening for urinary tract infections with aggressive treatment and for opportunistic infections that may affect the fetus is essential. Surveillance for fetal anomalies, growth, and antenatal testing is important. Steroids for fetal lung maturity are indicated for preterm delivery. Vaginal birth is preferred, reserving cesarean for obstetrical indications, with pain management similar to normal laboring patients. Surveillance for infection postpartum is warranted. Conflicting information exists regarding safety of breastfeeding with immunosuppressive drugs; immunosuppressive medication must be adjusted to prepregnancy levels and contraception counseling addressed.

Does Haart Improve Renal Function? An Association between Serum Cystatin C Concentration, HIV Viral Load and Haart Duration

Aim

The prevalence of renal disease in human HIV-infected individuals varies between 2% and 10%. Many reports have demonstrated the beneficial effect of anti-retroviral (ARV) therapy on slowing the progression of renal diseases. The aim of our cross-sectional study was to determine serum cystatin C concentration in different stages of HIV infection and the relationship between cystatin C concentration and ARV treatment.

Methods

Cystatin C concentration was measured in the sera of 77 HIV-1-infected individuals and 18 HIV-seronegative volunteers. The glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease Study formula.

Results

HIV infection resulted in a significant increase in serum cystatin C concentration compared with healthy individuals (933.4±32.1 vs 621.1 ±56.8 ng/ml, P<0.001). There were no significant differences in urea, creatinine and GFR between those groups. On multivariate analyses serum cystatin C was independently associated with highly active antiretroviral therapy (HAART) duration (β=-0.34, P=0.04) and HIV viral load (β=0.33, P=0.04), whereas there were no significant relationships with age, body mass index, HIV duration, CD4+ and CD8+ T-cell counts and serum high sensitivity C-reactive protein concentration.

Conclusions

Our initial observations indicate that serum cystatin C, which may reflect mild renal dysfunction, is increased during HIV-infection and is associated with HIV viral load. Long-lasting HAART seems to decrease cystatin C concentration, thus potentially improves renal function.