A systematic review assessing the potential use of cystatin c as a biomarker for kidney disease in people living with HIV on antiretroviral therapy

The introduction of antiretroviral therapy (ART) has significantly prolonged the lifespan of people living with human immunodeficiency virus (PLWH). However, the sustained use of this drug regimen has also been associated with a cluster of metabolic anomalies, including renal toxicity, which can lead to the development of kidney diseases. In this study, we reviewed studies examining kidney disease in PLWH sourced from electronic databases such as PubMed/MEDLINE, Scopus, and Google Scholar, as well as gray literature. The narrative synthesis of data from these clinical studies demonstrated that the serum levels of cystatin C remained unchanged or were not affected in PLWH on ART, while the creatinine-based glomerular filtration rate (GFR) fluctuated. In fact, some of the included studies showed that the creatinine-based GFR was increased in PLWH taking tenofovir disoproxil fumarate-containing ART, perhaps indicating that the use of both cystatin C- and creatinine-based GFRs is vital to monitor the development of kidney disease in PLWH. Clinical data summarized within this study indicate the potential detrimental effects of tenofovir-based ART regimens in causing renal tubular injury, while highlighting the possible beneficial effects of dolutegravir-based ART on improving the kidney function in PLWH. However, the summarized literature remains limited, while further clinical studies are required to provide insights into the potential use of cystatin C as a biomarker for kidney disease in PLWH.

Correcting eGFR for the effects of ART on tubular creatinine secretion: does one size fit all?

Several antiretrovirals including dolutegravir, rilpivirine and cobicistat inhibit tubular creatinine secretion, leading to benign increases in serum creatinine and reductions in estimated glomerular filtration rate (eGFR). This commentary discusses the magnitude and pattern of eGFR decline, whether this can be overcome by applying a standardized correction factor (as reported by Brunet et al. in Antiviral Therapy), the value of serial eGFR measures to detect rapid eGFR decline and the potential utility of cystatin C as an alternative biomarker of kidney function.

Cystatin C and Urine Albumin to Creatinine Ratio Predict 5-Year Mortality and Cardiovascular Events in People Living With HIV

BACKGROUND

Identifying people with HIV (PWH) at risk for chronic kidney disease, cardiovascular events, and death is crucial. We evaluated biomarkers to predict all-cause mortality and cardiovascular events, and measured glomerular filtration rate (mGFR) slope.

METHODS

Biomarkers were measured at enrollment. Baseline and 5-year mGFR were measured by plasma iohexol clearance. Outcomes were a composite criterion of all-cause mortality and/or cardiovascular events, and mGFR slope.

RESULTS

Of 168 subjects, 146 (87.4%) had undetectable HIV load. Median follow-up was 59.1 months (interquartile range, 56.2-62.1). At baseline, mean age was 49.5 years (± 9.8) and mean mGFR 98.9 mL/min/1.73m2 (± 20.6). Seventeen deaths and 10 cardiovascular events occurred during 5-year follow-up. Baseline mGFR was not associated with mortality/cardiovascular events. In multivariable analysis, cystatin C (hazard ratio [HR], 5.978; 95% confidence interval [CI], 2.774-12.88; P < .0001) and urine albumin to creatinine ratio (uACR) at inclusion (HR, 1.002; 95% CI, 1.001-1.004; P < .001) were associated with mortality/cardiovascular events. Area under receiver operating curve of cystatin C was 0.67 (95% CI, .55-.79) for mortality/cardiovascular event prediction. Biomarkers were not associated with GFR slope.

CONCLUSIONS

uACR and cystatin C predict all-cause mortality and/or cardiovascular events in PWH independently of mGFR.

[Cystatin C: Biomarker of cardiovascular risk in HIV]

INTRODUCTION

Patients infected with the human immunodeficiency virus (HIV) have a higher cardiovascular risk (CVR). The development of cardiovascular disease (CVD) in this population involves traditional CVR factors and factors related to the infection itself, such as chronic inflammatory status, immune dysfunction, as well as the antiretroviral therapy received. Cystatin C (CC) has shown to be useful in assessing the presence of CVR factors and CVD established in the general population, the elderly population, and patients with chronic kidney disease. An analysis was performed on this association in an HIV positive population (HIV+).

MATERIAL AND METHODS

Analytical, observational, cross-sectional study was conducted, and included collecting information about CVR factors and CVD in HIV+, as well as measuring CC. The patients were divided into 2 groups: Group1=high CC (≥0.95mg/L) and Group2=normal CC (<0.95mg/L).

RESULTS

A total of 95 patients were included. Group1=27 (28.4%) and Group2=68 (71.5%). A value of CC≥0.95mg/L was related to the presence of CVD (P=.01). It was also related with and an increase in waist circumference (P=.05), neck circumference (P=.04), systolic blood pressure (P=.04), diastolic blood pressure (P=.01), Framingham score (P=.03), and Framingham score adapted for HIV (P=.01). After performing multivariate analysis with incorporation of variables associated with CVD in the bivariate analysis, only CC≥0.95mg/L continued to be related to CVD.

CONCLUSION

CC≥0.95mg/L was independently associated with CVD. This cut-off point was also linked to higher levels of blood pressure, and higher CVR at 10 years using the Framingham Score and Framingham Score adapted for HIV population.

Kidney Disease in HIV Infection

Antiretroviral therapy (ART) has significantly improved life expectancy of infected subjects, generating a new epidemiological setting of people aging withHuman Immunodeficiency Virus (HIV). People living with HIV (PLWH), having longer life expectancy, now face several age-related conditions as well as side effects of long-term exposure of ART. Chronic kidney disease (CKD) is a common comorbidity in this population. CKD is a relentlessly progressive disease that may evolve toward end-stage renal disease (ESRD) and significantly affect quality of life and risk of death. Herein, we review current understanding of renal involvement in PLWH, mechanisms and risk factors for CKD as well as strategies for early recognition of renal dysfunction and best care of CKD.

Utility of cystatin C-based equations in patients undergoing dialysis

Serum cystatin C (CysC) measurement is regarded as a simple and practical alternative to measure residual renal function for dialysis patients. Recent studies have shown that CysC has better diagnostic accuracy or at least equivalence to creatinine in predicting the early stages of renal damage, and is closely related to clinical outcomes of dialysis patients. Thus, the applicability of CysC-derived equations in patients undergoing dialysis should be paid attention. Here, we review the role of CysC in diagnosis, renal function evaluation, and prognosis outcomes for dialysis patients, so as to provide them with useful suggestions on evaluating renal function and predicting adverse outcomes in clinical practice.

Impact of lean mass and bone density on glomerular filtration rate estimation in people living with HIV/AIDS

Context

Chronic kidney disease is a frequent complication in persons living with HIV/AIDS. Although previous studies have suggested that the CKD-EPI formula is appropriate to estimate glomerular filtration rate (GFR) in HIV-positive adults with normal kidney function, the optimal way to estimate GFR in those with Stage 3 chronic kidney disease is not known. Moreover, the impact of muscle mass on creatinine level and GFR estimation is unknown.

Aim and methods

Our study aimed to evaluate the accuracy of different diagnostic tests available compared to the gold standard measurement of GFR. A group of 44 HIV-1 patients with an estimated GFR between 60 and 30 ml/min/1.73 m² were included in a single-center cross-sectional study. Serum creatinine and cystatin C were measured. GFR was estimated using Cockcroft-Gault, MDRD, sMDRD, CKD-EPI, CKD-EPIcyst, and CKD-EPIcyst/creat formulae and was measured using isotopic Chrome₅₁ EDTA clearance. Bone density and muscle mass were measured by DXA scan.

Results

Mean age was 62±10 years. Mean BMI was 23±4 kg/m². Prevalence of diabetes was 30% and of hypertension was 47%. Viral load was <40 copies/ml for 90% of the patients, and mean CD₄ count was 446±191 cells/mm³. Mean measured GFR was 63.4±16.5 ml/min/1.73 m². All formulae under-estimated GFR. The best relative precision and accuracy were provided by the CKP-EPI formula. sMDRD, CKD-EPIcyst, and CKD-EPIcyst/creat performed worse than the CKD-EPI formula. Body composition did not significantly influence accuracy or precision of GFR estimation.

Conclusion

In HIV-infected patients in stable immunovirologic conditions with CKD stage 3 and high prevalence of metabolic associated conditions, the CKD-EPI formula performed best, although all formulae under estimate GFR.

Diagnostic challenges of kidney diseases in HIV-infected patients

INTRODUCTION

Chronic kidney disease (CKD) is a prevalent comorbidity in persons living with HIV infection (PLWH) associated with an increase in cardiovascular morbidity and all-cause mortality. Furthermore, early diagnosis of CKD is difficult in PLWH. Areas covered: We reviewed the main diagnostic tools for CKD in PLWH, and discussed their strengths and limits. We performed a literature search on PubMed to identify reviews and clinical trials dealing with attractive kidney biomarkers of CKD in PLWH, with the following key words: 'HIV AND kidney', 'HIV AND Kidney biomarkers', 'CKD AND Kidney biomarkers'. Expert commentary: Currently, CKD diagnosis is based on the estimation of Glomerular Filtration Rate (GFR), and measurement of proteinuria by urine protein/creatinine ratio (uPCR). These parameters are independent and complementary predictors of outcomes. GFR estimates are lacking in accuracy in PLWH. The best GFR estimate is CKD-EPI study equation. Moreover, low-grade proteinuria is associated with an increased risk of kidney disease progression in PLWH, and guidelines derived from the general population may lack sensitivity. Different biomarkers of kidney diseases like N-acetyl beta glucosaminidase (NAG), Kidney Injury Molecule-1 (KIM-1), and Alpha-1-microglobulin may predict kidney disease progression and mortality in PLWH. Others may help clinicians detect antiretroviral-induced tubulopathy, or predict cardiovascular events. More studies are needed to validate the routine use of these types of biomarkers.

CKD-EPI equation: A suitable Glomerular Filtration Rate estimate for drug dosing in HIV-infected patients

OBJECTIVES

To evaluate concordance between glomerular filtration rate (GFR) estimates (Cockcroft and Gault, modification of diet in renal diseases, chronic kidney disease epidemiology study group equations) for drug dosing in HIV-infected patients.

PATIENTS AND METHODS

We performed a monocentric study. GFR was measured using the gold standard method (plasma clearance of iohexol) in 230 HIV-infected patients. Concordance rate was evaluated between measured GFR (mGFR) and estimated GFR (eGFR) for different GFR categories (GFR>90 mL/min, GFR<90 mL/min, GFR>70 mL/min, and GFR<70 mL/min). MDRD and CKD-EPI were used with and without indexation to body surface area (BSA).

RESULTS

Mean age was 48±10 years, mean mGFR was 101±26 mL/min. Concordance between mGFR and eGFR estimated with CG, CKD-EPI (indexed and not indexed to BSA), or MDRD equations (not indexed to BSA) was similar (73%, 73%, 74%, and 73% respectively) for a breakpoint value of 90 mL/min for GFR. At this value, the concordance rate between mGFR and MDRD indexed to BSA was significantly lower (65%, P<0.05). Using 70 mL/min of GFR as the breakpoint value, all equations had similar concordance rates with mGFR (with or without indexation to BSA).

CONCLUSION

CKD-EPI equation has the same concordance with GFR and with CG when used for drug dosing.

Serum and urinary cystatin C in cats with feline immunodeficiency virus infection and cats with hyperthyroidism

OBJECTIVES

The objective of this study was to investigate serum cystatin C (sCysC) and urinary cystatin C (uCysC) in cats with hyperthyroidism and cats with feline immunodeficiency virus (FIV).

METHODS

Thirty cats with FIV, 26 hyperthyroid cats and 28 healthy cats were included. sCysC and uCysC:creatinine (uCysC/uCr) ratio were measured with a human particle-enhanced nephelometric immunoassay, previously validated for feline CysC measurement. Routine renal variables (serum creatinine [sCr], urine specific gravity, urinary protein:creatinine ratio [UPC]) were also measured in the three groups.

RESULTS

Cats with hyperthyroidism had significantly higher sCysC and higher uCysC/uCr ratio, lower sCr and a higher UPC than healthy cats. Cats with FIV infection did not show a significantly higher sCysC concentration but had a significantly higher sCr and UPC than healthy cats. uCysC could be detected in only four of them.

CONCLUSIONS AND RELEVANCE

This study demonstrated that sCysC is increased in cats with hyperthyroidism, in contrast with sCr, but not in cats with FIV. Many hyperthyroid cats, but only four cats with FIV, had an elevated uCysC/uCr ratio. Further studies may reveal if uCysC might be a valuable marker for tubular dysfunction in cats.

Markers of renal disease and function are associated with systemic inflammation in HIV infection

OBJECTIVES

Both renal disease and systemic inflammation predict non-AIDS-defining events and overall mortality in HIV-infected patients. Here, we sought to determine the relationships between renal disease and circulating inflammation markers.

METHODS

We performed a secondary analysis of AIDS Clinical Trials Group Study A5224s to determine if markers of renal disease [urine protein:creatinine ratio (uPCR), urine albumin:creatinine ratio (uACR), and estimated glomerular filtration rate (eGFR), using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine and cystatin C-creatinine] were associated with markers of systemic inflammation [high-sensitivity C-reactive protein, interleukin-6, tumour necrosis factor (TNF)-α, soluble TNF-α receptor I (sTNFRI), sTNFRII, and soluble vascular cellular and intercellular adhesion molecules]. We correlated these renal and inflammatory markers prior to antiretroviral initiation and after 96 weeks of therapy.

RESULTS

We found that eGFR (estimated using CKD-EPI cystatin C-creatinine), uPCR, and uACR were significantly correlated with most assessed markers of systemic inflammation prior to antiretroviral initiation. uPCR and eGFR (using CKD-EPI cystatin C-creatinine), but not uACR, remained significantly correlated with most of the assessed inflammatory markers after 96 weeks of antiretroviral therapy (ART). Most of these correlations, although statistically significant, were < 0.50. eGFR using CKD-EPI creatinine was much less frequently associated with inflammation markers and only significantly correlated with sTNFR1 at week 0 and with sTNFRI and II at week 96.

CONCLUSIONS

Renal disease and function were associated with systemic inflammation in HIV infection, both before and after ART. Systemic inflammation may partially explain the relationships between proteinuria, albuminuria, and reduced renal function and future adverse outcomes.

Reductions in Plasma Cystatin C After Initiation of Antiretroviral Therapy Are Associated With Reductions in Inflammation: ACTG A5224s

BACKGROUND

Among patients with HIV infection, changes in the kidney filtration marker cystatin C after initiation of antiretroviral therapy (ART) may be related to changes in body composition or biomarkers of inflammation.

METHODS

ACTG A5224s was a substudy of A5202, which randomly assigned ART-naive HIV-infected subjects to blinded abacavir/lamivudine (ABC/3TC) or tenofovir/emtricitabine (TDF/FTC) with open-label efavirenz (EFV) or ritonavir-boosted atazanavir. This analysis explored changes in cystatin C from 0 to 96 weeks.

RESULTS

Of the 269 subjects, 85% were male and 66% white non-Hispanics; baseline mean CD4 count was 236 cells per cubic millimeter and cystatin C was 0.89 mg/L. Cystatin C decreased significantly within each arm; however, ritonavir-boosted atazanavir attenuated the beneficial effects of ART on cystatin C compared to EFV. Compared to ABC/3TC, TDF/FTC led to a marginally significant attenuation for percent change analyses only. Higher baseline body mass index and HIV RNA were associated with larger reductions in cystatin C in multivariable models. At baseline, cystatin C was positively correlated with high-sensitivity C-reactive protein (Spearman r = 0.25), interleukin 6 (r = 0.34), soluble intercellular adhesion molecule (r = 0.36), soluble vascular cell adhesion molecule (r = 0.54), tumor necrosis factor α (r = 0.57), and soluble TNF-α receptor I (r = 0.70, all P < 0.001). Reductions in cystatin C from 0 to 96 weeks correlated with reductions in all inflammatory biomarkers (r = 0.39-0.58, P < 0.001) except for high-sensitivity C-reactive protein (r = 0.01, P = 0.89) and IL-6 (r = 0.08, P = 0.24).

CONCLUSIONS

The beneficial effect of ART on cystatin C concentrations is attenuated by boosted ATV when compared to EFV. Reductions in cystatin C after ART are associated with reductions in systemic inflammation.

The urinary proteome and metabonome differ from normal in adults with mitochondrial disease

We studied the extent and nature of renal involvement in a cohort of 117 adult patients with mitochondrial disease, by measuring urinary retinol-binding protein (RBP) and albumin; established markers of tubular and glomerular dysfunction, respectively. Seventy-five patients had the m.3243A>G mutation and the most frequent phenotypes within the entire cohort were 14 with MELAS, 33 with MIDD, and 17 with MERRF. Urinary RBP was increased in 29 of 75 of m.3243A>G patients, whereas albumin was increased in 23 of the 75. The corresponding numbers were 16 and 14, respectively, in the 42 non-m.3243A>G patients. RBP and albumin were higher in diabetic m.3243A>G patients than in nondiabetics, but there were no significant differences across the three major clinical phenotypes. The urine proteome (mass spectrometry) and metabonome (nuclear magnetic resonance) in a subset of the m.3243A>G patients were markedly different from controls, with the most significant alterations occurring in lysosomal proteins, calcium-binding proteins, and antioxidant defenses. Differences were also found between asymptomatic m.3243A>G carriers and controls. No patients had an elevated serum creatinine level, but 14% had hyponatremia, 10% had hypophosphatemia, and 14% had hypomagnesemia. Thus, abnormalities in kidney function are common in adults with mitochondrial disease, exist in the absence of elevated serum creatinine, and are not solely explained by diabetes.

How to assess kidney function in outpatient clinics

BACKGROUND

In 2002, a new definition and classification of chronic kidney disease was published, and glomerular filtration rate < 60 ml/min/1.73 m(2) for 3 months or more was adapted to define chronic kidney disease irrespective of other signs of kidney damage.

AIMS

To discuss different ways to assess kidney function in outpatient clinics and especially in primary care.

METHODS

The PubMed database was searched for relevant articles.

RESULTS

The estimated glomerular filtration rate equations which take into account plasma creatinine, age, sex, race and body size have been developed to identify patients with chronic kidney disease formerly overlooked if the renal function had been assessed by plasma creatinine alone. Cystatin C-based equations have also been developed to enhance accuracy for individuals with whom creatinine-based estimates for kidney function are acknowledged to be less accurate.

DISCUSSION

The characteristics of the patients to whom the diagnostic test is applied can influence the sensitivity of the test. Thus, there is nowadays controversy over the best method to assess kidney function in general population.

CONCLUSION

In the overwhelming majority of patients currently treated in primary care, the CKD-EPI creatinine equation is suitable for estimating renal function. The CKD-EPIcr-cys equation would provide further reliability in individuals with a CKD-EPI creatinine eGFR of 45-59 ml/min/1.73 m(2) , but the cost of serum cystatin C analysis limits its use in everyday general practice.

Protease Inhibitors and Renal Function in Patients with HIV Infection: a Systematic Review

INTRODUCTION

Despite antiretroviral (ARV) therapy reducing renal disease in human immunodeficiency virus overall, there is concern that certain ARVs, particularly tenofovir disoproxil fumarate (TDF) with or without a boosted protease inhibitor (PI), may reduce renal function over time. It is not known whether effects seen with PI-based regimens are independent, result from interactions with TDF coadministration, or are artefactual owing to inhibition of renal tubular creatinine transport by ritonavir or cobicistat pharmacoenhancement. The aim of this review was to conduct a systematic review of studies, weighted toward high-quality evidence, examining changes in renal function over time with PI-based regimens.

METHODS

PubMed, Embase, and Medline databases and conference abstracts were searched using pre-defined terms for English language articles, published up to and including August 12, 2013, describing changes in renal function over time with PI-based regimens. All available randomized controlled trials (RCTs) were selected; however, to reduce bias, only observational studies recruiting from more than one center and analyzing data from more than 1,000 patients were included. Evidence was qualitatively evaluated according to levels established by the Oxford Centre for Evidence-Based Medicine (OCEBM).

RESULTS

A total of 2,322 articles were retrieved by the initial search. Of these, 37 were selected for full review, comprising 24 RCTs (OCEBM Level 1 evidence: 4 reports of fully double-blinded or blinded with respect to the PI component). The remaining 20 RCTs and 13 observational studies qualified as OCEBM Level 2 evidence. Level 1 evidence showed initial but non-progressive increases in serum creatinine and corresponding decreases in estimated glomerular filtration rate (eGFR), suggesting an effect on renal tubular transport of creatinine. Level 2 evidence suggested that atazanavir and lopinavir especially in combination with TDF were associated with non-progressive reductions in eGFR over time, with a decreased risk for the development of chronic kidney disease (CKD) on cessation and without the development of advanced CKD or end-stage renal disease (ESRD); whether these reductions were independent or associated with interactions with coadministered TDF could not be established with certainty. Data on darunavir were insufficient to draw any conclusions. The principal limitation of the reviewed studies was the lack of standardization of creatinine measurements in virtually all studies and the lack of corroborative data on changes in proteinuria or other indices of renal function.

DISCUSSION

In this review, there was little evidence for progressive changes in eGFR, or the development of advanced CKD, or ESRD with lopinavir or atazanavir. Further long-term studies, employing a wide range of validated renal function assessments, are required to fully evaluate potential association of PIs with CKD.

A consensus statement on the renal monitoring of Australian patients receiving tenofovir based antiviral therapy for HIV/HBV infection

A number of antiviral agents used against Human Immunodeficiency Virus (HIV) infection and hepatitis B virus (HBV) mono or co-infection have been associated with real nephrotoxicity (including tenofovir disoproxil fumarate (TDF), atazanavir, indinavir and lopinavir) or apparent changes in renal function (e.g. cobicistat, ritonavir, rilpivirine and dolutegravir). Patients with HIV are at higher risk of acute and chronic renal dysfunction, so baseline assessment and ongoing monitoring of renal function is an important part of routine management of patients with HIV.

Given the paucity of evidence in this area, we sought to establish a consensus view on how routine monitoring could be performed in Australian patients on ART regimens, especially those involving TDF. A group of nephrologists and prescribers (an HIV physician and a hepatologist) were assembled by Gilead to discuss practical and reasonable renal management strategies for patients particularly those on TDF-based combination regimens (in the case of those with HIV-infection) or on TDF-monotherapy (in the case of HBV-mono infection). The group considered which investigations should be performed as part of routine practice, their frequency, and when specialist renal referral is warranted. The algorithm presented suggests testing for serum creatinine along with plasma phosphate and an assessment of urinary protein (rather than albumin) and glucose.

Here we advocate baseline tests of renal function at initiation of therapy. If creatinine excretion inhibitors (e.g. cobicistat or rilpivirine) are used as part of the ART regimen, we suggest creatinine is rechecked at 4 weeks and this value used as the new baseline. Repeat testing is suggested at 3-monthly intervals for a year and then at least yearly thereafter if no abnormalities are detected. In patients with abnormal baseline results, renal function assessment should be performed at least 6 monthly. In HBV mono-infected patients advocate that a similar testing protocol may be logical.

Cystatin C-based renal function changes after antiretroviral initiation: a substudy of a randomized trial

BACKGROUND

The effects of antiretrovirals on cystatin C-based renal function estimates are unknown.

METHODS

We analyzed changes in renal function using creatinine and cystatin C-based estimating equations in 269 patients in A5224s, a substudy of study A5202, in which treatment-naive patients were randomized to abacavir/lamivudine or tenofovir/emtricitabine with open-label atazanavir/ritonavir or efavirenz.

RESULTS

Changes in renal function significantly improved (or declined less) with abacavir/lamivudine treatment compared with tenofovir/emtricitabine using the Cockcroft-Gault formula (P = .016) and 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI; P = .030) and 2012 CKD-EPI cystatin C-creatinine (P = .025). Renal function changes significantly improved (or declined less) with efavirenz compared with atazanavir/ritonavir (P < .001 for all equations). Mean (95% confidence interval) renal function changes specifically for tenofovir/emtricitabine combined with atazanavir/ritonavir were -8.3 (-14.0, -2.6) mL/min with Cockcroft-Gault; -14.9 (-19.7, -10.1) mL/min per 1.73(2) with Modification of Diet in Renal Disease; -12.8 (-16.5, -9.0) mL/min per 1.73(2) with 2009 CKD-EPI; +8.9 (4.2, 13.7) mL/min per 1.73(2) with 2012 CKD-EPI cystatin C; and -1.2 (-5.1, 2.6) mL/min per 1.73(2) with 2012 CKD-EPI cystatin C-creatinine. Renal function changes for the other treatment arms were more favorable but similarly varied by estimating equation.

CONCLUSIONS

Antiretroviral-associated changes in renal function vary in magnitude and direction based on the estimating equation used.

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.

HIV viremia and T-cell activation differentially affect the performance of glomerular filtration rate equations based on creatinine and cystatin C

BACKGROUND

Serum creatinine and cystatin C are used as markers of glomerular filtration rate (GFR). The performance of these GFR markers relative to exogenously measured GFR (mGFR) in HIV-positive individuals is not well established.

METHODS

We assessed the performance of the chronic kidney disease epidemiology collaboration equations based on serum concentrations of creatinine (eGFRcr), cystatin C (eGFRcys) and both biomarkers combined (eGFRcr-cys) in 187 HIV-positive and 98 HIV-negative participants. Measured GFR was calculated by plasma iohexol clearance. Bias and accuracy were defined as the difference between eGFR and mGFR and the percentage of eGFR observations within 30% of mGFR, respectively. Activated CD4 and CD8 T-cells (CD38+ HLA-DR+) were measured by flow cytometry.

RESULTS

The median mGFR was >100 ml/min/1.73 m(2) in both groups. All equations tended to be less accurate in HIV-positive than in HIV-negative subjects, with eGFRcr-cys being the most accurate overall. In the HIV-positive group, eGFRcys was significantly less accurate and more biased than eGFRcr and eGFRcr_cys. Additionally eGFRcys bias and accuracy were strongly associated with use of antiretroviral therapy, HIV RNA suppression, and percentages of activated CD4 or CD8 T-cells. Hepatitis C seropositivity was associated with larger eGFRcys bias in both HIV-positive and HIV-negative groups. In contrast, eGFRcr accuracy and bias were not associated with HIV-related factors, T-cell activation, or hepatitis C.

CONCLUSIONS

The performance of eGFRcys relative to mGFR was strongly correlated with HIV treatment factors and markers of T-cell activation, which may limit its usefulness as a GFR marker in this population.

A review of cardiovascular and renal function monitoring: a consideration of older adults with HIV

The prevalence of human immunodeficiency virus (HIV) infection in older and elderly adults is significant worldwide. This population poses new challenges and opportunities in the management of HIV. In addition to the risks affecting HIV patients of all ages, including risk of opportunistic infection and medication resistance, age-related changes in physiology, higher comorbidity burdens, increased use of medications, and potential adverse drug reactions to HIV medications all factor into the care of older adults with HIV. The risk and progression of cardiovascular and renal comorbidities may be higher in the older adult HIV population and in patients taking specific HIV medications. Understanding these risks is essential when managing a new type of patient: the older adult with HIV.

Performance of creatinine and cystatin C-based glomerular filtration rate estimating equations in a European HIV-positive cohort

OBJECTIVE

To validate glomerular filtration rate (GFR) estimating equations in white HIV-infected patients based on serum creatinine and/or serum cystatin C.

DESIGN

Single-center, cross-sectional evaluation of the predictive performance of GFR estimators.

METHODS

GFR was measured by iohexol plasma clearance. Serum creatinine (Scr) and serum cystatin C (Scyst) were measured by traceable and standardized methods. We evaluated the performance of the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations. We also studied the performance of the cystatin C-based equation (CKD-EPI Scyst) and the combined cystatin and creatinine-based equation (CKD-EPI combined), as recently proposed by the CKD-EPI group.

RESULTS

Two hundred and three participants (18% of women) were included. Mean age was 49 ± 10 years. Mean measured GFR (mGFR) was 95 ± 24 ml/min per 1.73 m². CKD-EPI and CKD-EPI combined significantly outperformed the MDRD equation. The percentage of estimating results within 30% of mGFR was 75, 82 and 81% for the MDRD, CKD-EPI and CKD-EPI combined equation, respectively. Results favoring the CKD-EPI and CKD-EPI combined equation were especially observed for patients with mGFR over 90 ml/min per 1.73 m².

CONCLUSION

In our European HIV cohort, we confirmed that the creatinine-based CKD-EPI equation should replace the MDRD study equation. However, global performance of this equation remains worse than the performance observed in the general population. This lesser performance is particularly relevant in patients with measured GFR under and around 60 ml/min per 1.73 m². Moreover, the specific interest of Scyst-based equations is not confirmed in this population.

Prevalence of proteinuria and elevated serum cystatin C among HIV-Infected Adolescents in the Reaching for Excellence in Adolescent Care and Health (REACH) study

OBJECTIVE

In the United States, kidney dysfunction is prevalent in almost 30% of HIV-infected patients and is an independent predictor of mortality. Proteinuria and elevated serum cystatin C (eCysC) are used as markers of kidney disease in the general population; however, the prevalence of these markers in HIV-infected adolescents is largely unknown.

METHODS

This study includes 304 HIV-infected adolescents from the Reaching for Excellence in Adolescent Care and Health (REACH) cohort, an observational study of adolescents recruited from 13 US cities. Clinical and demographic characteristics of participants were evaluated as correlates of proteinuria, a urine protein to creatinine ratio of ≥200 mg/g. Select univariate predictors were assessed to determine the association with urinary protein excretion and serum cystatin C in multivariable linear regression models and proteinuria and eCysC (eCysC ≥ 75th percentile) in multivariable logistic regression models.

RESULTS

Overall, 19.1% of the participants had proteinuria, whereas 23.7% had an eCysC. Low CD4 T-lymphocyte counts (<200 cells/mm) were significantly associated with a greater urine protein to creatinine ratio in linear models and with proteinuria in logistic regression models. CD4 T-lymphocyte counts <500 cells/mm were significantly associated with a greater serum cystatin C concentration in linear models and with eCysC in logistic regression models.

CONCLUSIONS

Proteinuria among HIV-infected adolescents in the REACH cohort was approximately 2-fold greater than healthy US adolescents. Both proteinuria and eCysC are associated with CD4 T-lymphocyte counts. Further studies investigating early markers of kidney disease and the association with immune status and inflammation in HIV-infected adolescents are needed.

Renal dysfunction in the setting of HIV/AIDS

Antiretroviral therapy has been immensely successful in reducing the incidence of opportunistic infections and death after HIV infection. This has resulted in heightened interest in noninfectious comorbidities including kidney disease. Although HIV-associated nephropathy, the most ominous kidney disease related to the direct effects of HIV, may be prevented and treated with antiretrovirals, kidney disease remains an important issue in this population. In addition to the common risk factors for kidney disease of diabetes mellitus and hypertension, HIV-infected individuals have a high prevalence of other risk factors, including hepatitis C and exposure to antiretrovirals and other medications. Therefore, the differential diagnosis is vast. Early identification (through efficient screening) and prompt treatment of kidney disease in HIV-infected individuals are critical to lead to better outcomes. This review focuses on clinical and epidemiological issues, treatment strategies (including dialysis and kidney transplantation), and recent advances among kidney disease in the HIV population.