Comparisons of creatinine and cystatin C for detection of kidney disease and prediction of all-cause mortality in HIV-infected women

The predictive accuracy of machine learning for the risk of death in HIV patients: a systematic review and meta-analysis

BACKGROUND

Early prediction of mortality in individuals with HIV (PWH) has perpetually posed a formidable challenge. With the widespread integration of machine learning into clinical practice, some researchers endeavor to formulate models predicting the mortality risk for PWH. Nevertheless, the diverse timeframes of mortality among PWH and the potential multitude of modeling variables have cast doubt on the efficacy of the current predictive model for HIV-related deaths. To address this, we undertook a systematic review and meta-analysis, aiming to comprehensively assess the utilization of machine learning in the early prediction of HIV-related deaths and furnish evidence-based support for the advancement of artificial intelligence in this domain.

METHODS

We systematically combed through the PubMed, Cochrane, Embase, and Web of Science databases on November 25, 2023. To evaluate the bias risk in the original studies included, we employed the Predictive Model Bias Risk Assessment Tool (PROBAST). During the meta-analysis, we conducted subgroup analysis based on survival and non-survival models. Additionally, we utilized meta-regression to explore the influence of death time on the predictive value of the model for HIV-related deaths.

RESULTS

After our comprehensive review, we analyzed a total of 24 pieces of literature, encompassing data from 401,389 individuals diagnosed with HIV. Within this dataset, 23 articles specifically delved into deaths during long-term follow-ups outside hospital settings. The machine learning models applied for predicting these deaths comprised survival models (COX regression) and other non-survival models. The outcomes of the meta-analysis unveiled that within the training set, the c-index for predicting deaths among people with HIV (PWH) using predictive models stands at 0.83 (95% CI: 0.75-0.91). In the validation set, the c-index is slightly lower at 0.81 (95% CI: 0.78-0.85). Notably, the meta-regression analysis demonstrated that neither follow-up time nor the occurrence of death events significantly impacted the performance of the machine learning models.

CONCLUSIONS

The study suggests that machine learning is a viable approach for developing non-time-based predictions regarding HIV deaths. Nevertheless, the limited inclusion of original studies necessitates additional multicenter studies for thorough validation.

Soluble Insulin Receptor Levels in Plasma, Exosomes, and Urine and Its Association With HIV-Associated Neurocognitive Disorders

Background

HIV-associated neurocognitive disorders (HAND) are one of the HIV-associated comorbidities affecting 20-50% of the people with HIV (PWH) infection. We found that the soluble insulin receptor (sIR) levels in plasma and cerebrospinal fluid (CSF) were significantly higher in HIV-infected women. The mechanism of sIR release into the plasma remains unknown, but the detection of the sIR in exosomes may uncover novel mechanisms of sIR secretion from HIV-infected cells and its contribution to HIV disease progression and HAND development. Quantification of sIR in urine may represent a less invasive and more accessible diagnostic tool. Our objective was to quantify sIR levels in plasma, plasma-derived exosomes, and urine, and evaluate their association with HAND and renal function.

Methods

We measured full-length sIR in the plasma and urine of 38 controls and 76 HIV-infected women by ELISA, and sIR, HIV-1 Tat, and reactive oxygen species (ROS) in exosomes by flow cytometry.

Results

Plasma and exosomes with sIR were significantly higher in HIV-infected women when compared with controls and HAND. Exosomal sIR positively correlated with exosomal ROS and exosomal HIV-1 Tat in HIV-infected women. Exosomal ROS was significantly higher in HIV-infected women with more symptomatic cognitive impairment. Plasma-derived exosomes exhibited significantly higher levels of astrocyte (GFAP) and neuronal (L1CAM) markers in HIV-infected women, confirming the presence of circulating CNS-derived exosomes in the blood of HIV-infected women. Urine sIR positively correlated with eGFR in controls, but not in HIV-infected women, regardless there was no significant difference in renal function as determined by the estimated glomerular filtration rate (eGFR, p = 0.762). In HIV-infected women, higher plasma sIR correlated with lower urine sIR that could suggest sIR retention in blood or decreased renal filtration.

Discussion

Higher plasma sIR levels and their correlation with ROS in plasma-derived exosomes with HAND suggest a combined role of metabolic disturbances, oxidative stress, exosome release, and cognitive decline. Communication between CNS and periphery is compromised in PWH, thus plasma-derived exosomes may shed light on disrupted cellular mechanisms in the brain of PWH. High plasma and low urine sIR levels could suggest sIR retention in blood or decreased renal filtration.

Construction and validation of a prognostic nomogram for predicting the survival of HIV/AIDS adults who received antiretroviral therapy: a cohort between 2003 and 2019 in Nanjing

BACKGROUND

Great achievements have been achieved by free antiretroviral therapy (ART). A rapid and accurate prediction of survival in people living with HIV/AIDS (PLHIV) is needed for effective management. We aimed to establish an effective prognostic model to forecast the survival of PLHIV after ART.

METHODS

The participants were enrolled from a follow-up cohort over 2003-2019 in Nanjing AIDS Prevention and Control Information System. A nested case-control study was employed with HIV-related death, and a propensity-score matching (PSM) approach was applied in a ratio of 1:4 to allocate the patients. Univariable and multivariable Cox proportional hazards analyses were performed based on the training set to determine the risk factors. The discrimination was qualified using the area under the curve (AUC) and concordance index (C-Index). The nomogram was calibrated using the calibration curve. The clinical benefit of prognostic nomogram was assessed by decision curve analysis (DCA).

RESULTS

Predictive factors including CD4 cell count (CD4), body mass index (BMI) and hemoglobin (HB) were determined and incorporated into the nomogram. In the training set, AUC and C-index (95% CI) were 0.831 and 0.798 (0.758, 0.839), respectively. The validation set revealed a good discrimination with an AUC of 0.802 and a C-index (95% CI) of 0.786 (0.681, 0.892). The calibration curve also exhibited a high consistency in the predictive power (especially in the first 3 years after ART initiation) of the nomogram. Moreover, DCA demonstrated that the nomogram was clinically beneficial.

CONCLUSION

The nomogram is effective and accurate in forecasting the survival of PLHIV, and beneficial for medical workers in health administration.

Kidney tubule health scores and their associations with incident CKD in women living with HIV

OBJECTIVES

Individual kidney tubule biomarkers are associated with chronic kidney disease (CKD) risk in people living with HIV (PLWH). Whether a combination of kidney biomarkers can be integrated into informative summary scores for PLWH is unknown.

METHODS

We measured eight urine biomarkers of kidney tubule health at two visits over a 3-year period in 647 women living with HIV in the Women's Interagency Health Study. We integrated biomarkers into factor scores using exploratory factor analysis. We evaluated associations between CKD risk factors and factor scores, and used generalized estimating equations to determine associations between factor scores and risk of incident CKD.

RESULTS

Factor analysis identified two unique factor scores: a tubule reabsorption score comprising alpha-1-microglobulin, beta-2-microglobulin and trefoil factor-3; and a tubule injury score comprising interleukin-18 and kidney injury molecule-1. We modelled the two factor scores in combination with urine epidermal growth factor (EGF) and urine albumin. Predominantly HIV-related CKD risk factors were independently associated with worsening tubule reabsorption scores and tubule injury scores. During a median follow-up of 7 years, 9.7% (63/647) developed CKD. In multivariable time-updated models that adjusted for other factor scores and biomarkers simultaneously, higher tubule reabsorption scores [risk ratio (RR) = 1.27, 95% confidence interval (CI): 1.01-1.59 per 1 SD higher time-updated score], higher tubule injury scores (RR = 1.36, 95% CI: 1.05-1.76), lower urine EGF (RR = 0.75, 95% CI: 0.64-0.87), and higher urine albumin (RR = 1.20, 95% CI: 1.02-1.40) were jointly associated with risk of incident CKD.

CONCLUSIONS

We identified two novel and distinct dimensions of kidney tubule health that appear to quantify informative metrics of CKD risk in PLWH.

Estimation of renal function by three CKD-EPI equations in Chinese HIV/AIDS patients: A STROBE-compliant article

Assessing renal function accurately is important for human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) patients. Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recommended three equations to calculate estimated glomerular filtration rate (eGFR). There is evidence that eGFR based on the combination of serum creatinine and cystatin C is the most accurate of the three equations. But there is limited data on the comparison of three CKD-EPI equations in Chinese HIV/AIDS patients. The aim of our study was to compare the three CKD-EPI equations in Chinese HIV/AIDS population and assess renal function.Cross-sectional, single center, prospective study.One hundred seventy two Chinese adult HIV/AIDS patients were enrolled, including 145 (84.3%) males and 27 (15.7%) females. Mean age was 40(±12) years old. Overall mean eGFR based on serum creatinine, cystatin C and the combination of the 2 markers was 112.6(±19.0) mL/min/1.73 m2, 92.0(±24.2)mL/min/1.73 m2, and 101.7(±21.8)mL/min/1.73 m2, respectively (P = .000). The eGFR calculated by serum creatinine alone is higher than eGFR calculated by combination of serum creatinine and cystatin C, and eGFR calculated by cystatin C individual is lower than eGFR calculated by combination of the 2 markers.Of the 3 CKD-EPI equations, the CKD-EPIscr-cys equation may have the most accuracy in evaluating renal function in Chinese HIV/AIDS patients while the CKD-EPIscr equation may overestimate renal function and the CKD-EPIcys equation may underestimate renal function.

Urine Biomarkers of Kidney Tubule Health and Incident CKD Stage 3 in Women Living With HIV: A Repeated Measures Study

Rationale & Objective

Single measurements of urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in HIV infection, but the prognostic value of repeat measurements over time is unknown.

Study Design

Cohort study.

Setting & Participants

647 women living with HIV infection enrolled in the Women’s Interagency Health Study.

Exposures

14 urinary biomarkers of kidney tubule health measured at 2 visits over a 3-year period.

Outcome

Incident CKD, defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² at two 6-month visits and an average eGFR decline ≥ 3% per year.

Analytical Approach

We used multivariable generalized estimating equations adjusting for CKD risk factors to evaluate baseline, time-updated, and change-over-time biomarker associations with incident CKD. We compared CKD discrimination between models with and without a parsimoniously selected set of biomarkers.

Results

During a median 7 years of follow-up, 9.7% (63/647) developed CKD. In multivariable-adjusted analyses, 3 of 14 baseline biomarkers associated with incident CKD. In contrast, 10 of 14 time-updated biomarkers and 9 of 14 biomarkers modeled as change over time associated with incident CKD. Urinary epidermal growth factor (EGF), α₁-microglobulin (A1M), and albumin were selected using penalized regression methods. In the time-updated model, lower urinary EGF (risk ratio [RR] per 2-fold higher time-updated biomarker levels, 0.69; 95% CI, 0.58-0.81), higher urinary A1M (RR, 1.47; 95% CI, 1.25-1.73), and higher urinary albumin excretion (RR, 1.21; 95% CI, 1.03-1.42) were jointly associated with increased risk for CKD. Compared with a base model (C statistic, 0.75), CKD discrimination improved after adding urinary EGF, A1M, and albumin values across baseline (C = 0.81), time-updated (C = 0.83), and change-over-time (C = 0.83) models (P < 0.01 for all).

Limitations

Observational design, incident CKD definition limited to eGFR.

Conclusions

Repeat urinary biomarker measurements for kidney tubule health have stronger associations with incident CKD compared with baseline measurements and moderately improve CKD discrimination in women living with HIV infection.

Brief Report: Cystatin C-Based Estimation of Glomerular Filtration Rate and Association With Atherosclerosis Imaging Markers in People Living With HIV

INTRODUCTION

Reduced estimated glomerular filtration rate (eGFR) is associated with increased risk of cardiovascular disease among people living with HIV (PLWH). It is unclear whether eGFR equations incorporating cystatin C (CysC) measurements are more predictive of preclinical cardiovascular disease than those using only creatinine (Cr).

OBJECTIVES

The study aimed to determine which of the 3 Chronic Kidney Disease Epidemiology (CKD-EPI) eGFR equations is most associated with carotid intima media thickness (CIMT) and coronary artery calcium (CAC) score.

METHODS

This cross-sectional analysis of pooled data from 3 large cohorts compared the associations between the 3 CKD-EPI eGFR equations (Cr, CysC, and Cr-CysC) with CIMT and CAC score using multivariable regression analysis. eGFR and CIMT were analyzed as continuous variables. CAC scores were analyzed as a binary variable (detectable calcification versus nondetectable) and as a log10 Agatston score in those with detectable CAC.

RESULTS

Thousand four hundred eighty-seven participants were included, and of these 910 (562 HIV+ and 348 HIV-) had CIMT measurements and 366 (296 HIV+ and 70 HIV-) had CAC measurements available. In HIV- participants, GFR estimated by any CKD-EPI equation did not significantly correlate with CIMT or CAC scores. When PLWH were analyzed separately including HIV-specific factors, only GFR estimated using Cr-Cys C correlated with CIMT [β= -0.90, 95% CI: (-1.67 to -0.13) μm; P = 0.023]. Similarly, eGFR correlated with Agatston scores only when using cystatin C-based eGFR [β= -8.63, 95% CI: (-16.49 to -0.77) HU; P = 0.034]. Associations between other eGFR formulas and CAC did not reach statistical significance.

CONCLUSIONS

In PLWH, preclinical atherosclerosis may be more closely correlated with eGFR using formulae that incorporate CysC measurements than Cr alone.

Association of Statin Use With Kidney Damage and Function Among HIV-Infected Men

BACKGROUND

Chronic kidney disease (CKD) occurs commonly among HIV-infected persons. Statins may delay CKD onset and progression through their cholesterol-lowering and pleiotropic effects.

METHODS

Among 850 HIV-infected men from the Multicenter AIDS Cohort Study with stored urine samples (2009-2011), we evaluated cross-sectional associations of statin use with urine biomarkers of kidney damage [albumin-to-creatinine ratio (ACR), alpha-1-microglobulin, interleukin-18, kidney injury molecule-1, and procollagen type III N-terminal propeptide] using multivariable linear regression. We evaluated the longitudinal associations of statin use with annual change in estimated glomerular filtration rate by creatinine (eGFR) using linear mixed models, and with incident proteinuria and incident CKD (eGFR <60 mL/min/1.73 m) using Cox proportional hazards regression. We used inverse probability weighting to address potential confounding related to statin use.

RESULTS

Statin users comprised 30% of participants. In adjusted analyses, each year of cumulative statin use was associated with 4.0% higher baseline ACR levels (P = 0.05), but there was no association with baseline levels of other urine biomarkers. Statin use had no overall association with annual eGFR decline. Among participants with baseline proteinuria, statin use was modestly associated with slower annual eGFR decline compared to non-use (adjusted difference: 1.33 mL/min/1.73 m per year; 95% confidence interval: -0.07 to 2.70). Statin use was not associated with risk of incident proteinuria or incident CKD.

CONCLUSIONS

Statin use was associated with higher baseline ACR, but not with biomarkers of tubulointerstitial injury. Statin use was associated with modestly slower eGFR decline only among participants with baseline proteinuria. Although these findings may be susceptible to confounding by indication, they suggest a limited effect of statins on CKD risk among HIV-infected men.

Associations of Urine Biomarkers with Kidney Function Decline in HIV-Infected and Uninfected Men

BACKGROUND

HIV-infected (HIV+) persons are at increased risk of chronic kidney disease, but serum creatinine does not detect early losses in kidney function. We hypothesized that urine biomarkers of kidney damage would be associated with subsequent changes in kidney function in a contemporary cohort of HIV+ and HIV-uninfected (HIV-) men.

METHODS

In the Multicenter AIDS Cohort Study, we measured baseline urine concentrations of 5 biomarkers from 2009 to 2011 in 860 HIV+ and 337 HIV- men: albumin, alpha-1-microglobulin (α1m), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), and procollagen type III N-terminal propeptide (PIIINP). We evaluated associations of urine biomarker concentrations with annual changes in estimated glomerular filtration rate (eGFR) using multivariable linear mixed models adjusted for demographics, traditional kidney disease risk factors, HIV-related risk factors, and baseline eGFR.

RESULTS

Over a median follow-up of 4.8 years, the average annual eGFR decline was 1.42 mL/min/1.73 m2/year in HIV+ men and 1.22 mL/min/1.73 m2/year in HIV- men. Among HIV+ men, the highest vs. lowest tertiles of albumin (-1.78 mL/min/1.73 m2/year, 95% CI -3.47 to -0.09) and α1m (-2.43 mL/min/1.73 m2/year, 95% CI -4.14 to -0.73) were each associated with faster annual eGFR declines after multivariable adjustment. Among HIV- men, the highest vs. lowest tertile of α1m (-2.49 mL/min/1.73 m2/year, 95% CI -4.48 to -0.50) was independently associated with faster annual eGFR decline. Urine IL-18, KIM-1, and PIIINP showed no independent associations with eGFR decline, regardless of HIV serostatus.

CONCLUSIONS

Among HIV+ men, higher urine albumin and α1m are associated with subsequent declines in kidney function, independent of eGFR.

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.

Systolic blood pressure, routine kidney variables and renal ultrasonographic findings in cats naturally infected with feline immunodeficiency virus

Objectives Hypertension is a common cause of proteinuria in HIV-infected people. In cats, feline immunodeficiency virus (FIV) infection appears to be associated with proteinuria. Therefore, the results from systolic blood pressure (SBP) measurements in naturally infected FIV-positive cats were reviewed to assess whether hypertension contributes to the observed proteinuria in these cats. Ultrasonographic findings in FIV-positive cats were reviewed to complete renal assessment and to extend the scant knowledge on renal ultrasonography in cats. Methods Data from client-owned, naturally infected FIV-positive cats were retrospectively reviewed. To obtain a control group, records were reviewed from age-matched, privately owned, FIV-negative cats. Results Data from 91 FIV-infected and 113 control cats were compared. FIV-infected cats showed a significantly lower SBP ( P <0.0001) and significantly fewer FIV-infected cats were hypertensive (⩾160 mmHg) compared with control cats ( P = 0.025). The prevalence of renal azotaemia did not significantly differ between groups, although FIV-infected cats had significantly lower urine specific gravity (USG) ( P = 0.0273) and a higher incidence of USG below 1.035 ( P = 0.043). Urinary protein:creatinine ratio (UPC) was significantly higher in FIV-infected cats ( P = 0.0005) and proteinuria (UPC >0.4) occurred more frequently in FIV-infected cats ( P <0.001). Renal ultrasonography showed abnormalities in 60/91 FIV-infected cats, with hyperechogenic cortices in 39/91 and enlarged kidneys in 31/91. Conclusions and relevance Hypertension can be excluded as a common cause of renal damage leading to proteinuria in FIV-infected cats. Proteinuria and poorly concentrated urine are common in naturally infected FIV-positive cats, in contrast to azotaemia. Clinicians should cautiously interpret ultrasonographic abnormalities as these occur in over half of FIV-infected cats.

Cystatin C Falsely Underestimated GFR in a Critically Ill Patient with a New Diagnosis of AIDS

Cystatin C has been suggested to be a more accurate glomerular filtration rate (GFR) surrogate than creatinine in patients with acquired immunodeficiency syndrome (AIDS) because it is unaffected by skeletal muscle mass and dietary influences. However, little is known about the utility of this marker for monitoring medications in the critically ill. We describe the case of a 64-year-old female with opportunistic infections associated with a new diagnosis of AIDS. During her course, she experienced neurologic, cardiac, and respiratory failure; yet her renal function remained preserved as indicated by an eGFR ≥ 120 mL/min and a urine output > 1 mL/kg/hr without diuresis. The patient was treated with nephrotoxic agents; therefore cystatin C was assessed to determine if cachexia was resulting in a falsely low serum creatinine. Cystatin C measured 1.50 mg/L which corresponded to an eGFR of 36 mL/min. Given the >60 mL/min discrepancy, serial 8-hour urine samples were collected and a GFR > 120 mL/min was confirmed. It is unclear why cystatin C was falsely elevated, but we hypothesize that it relates to the proinflammatory state with AIDS, opportunistic infections, and corticosteroids. More research is needed before routine use of cystatin C in this setting can be recommended.

Racial Disparities in Creatinine-based Kidney Function Estimates Among HIV-infected Adults

OBJECTIVE

The aim of our study was to investigate whether current eGFR equations in clinical use might systematically over-estimate the kidney function, and thus misclassify CKD status, of Black Americans with HIV. Specifically, we evaluated the impact of removing the race coefficient from the MDRD and CKD-EPI equations on comparisons between Black and White HIV-infected veterans related to: 1) the prevalence of reduced eGFR; 2) the distribution of eGFR values; and 3) the relationship between eGFR and all-cause mortality.

DESIGN

Retrospective cohort study.

SETTING

The Department of Veterans Affairs (VA) HIV Clinical Case Registry (CCR), which actively monitors all HIV-infected persons receiving care in the VA nationally.

PATIENT/PARTICIPANTS

21,905 treatment-naïve HIV-infected veterans.

MAIN OUTCOME MEASURES

Estimated glomerular filtration rate (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) formula with and without (MDRD-RCR) the race coefficient and all-cause mortality.

RESULTS

Persons with eGFR <45 mL/min/1.73m(2) had a higher risk of death compared with those with eGFR >80 mL/min/1.73m(2) among both Blacks (HR=2.8, 95%CI: 2.4-3.3) and Whites (HR=1.9, 95%CI: 1.4-2.6), but the association appeared to be stronger in Blacks (P=.038, test for interaction). Blacks with eGFR 45-60 mL/min/1.73m(2) also had a higher risk of death (HR=1.7, 95%CI: 1.4-2.1) but Whites did not (HR=.86, 95%CI: .67-1.10; test for interaction: P<.0001). Racial differences were substantially attenuated when eGFR was re-calculated without the race coefficient.

CONCLUSIONS

Our findings suggest that clinicians may want to consider estimating glomerular filtration rate without the race coefficient in Blacks with HIV.

Correlation of cystatin C and creatinine based estimates of renal function in children with hydronephrosis

INTRODUCTION

The use of a simple and accurate glomerular filtration rate (GFR) estimating method aiming minute assessment of renal function can be of great clinical importance.

OBJECTIVES

This study aimed to determine the association of a GFR estimating by equation that includes only cystatin C (Gentian equation) to equation that include only creatinine (Schwartz equation) among children.

PATIENTS AND METHODS

A total of 31 children aged from 1 day to 5 years with the final diagnosis of unilateral or bilateral hydronephrosis referred to Besat hospital in Hamadan, between March 2010 and February 2011 were consecutively enrolled. Schwartz and Gentian equations were employed to determine GFR based on plasma creatinine and cystatin C levels, respectively.

RESULTS

The proportion of GFR based on Schwartz equation was 70.19± 24.86 ml/min/1.73 m(2), while the level of this parameter based on Gentian method and using cystatin C was 86.97 ± 21.57 ml/min/1.73 m(2). The Pearson correlation coefficient analysis showed a strong direct association between the two levels of GFR measured by Schwartz equation based on serum creatinine level and Gentian method and using cystatin C (r = 0.594, P < 0.001). The linear association between GFR values measured with the two methods included cystatin C based GFR = 50.8+ 0.515 × Schwartz GFR. The correlation between GFR values measured by using serum creatinine and serum cystatin C measurements remained meaningful even after adjustment for patients' gender and age (r = 0.724, P < 0.001).

CONCLUSION

The equation developed based on cystatin C level is comparable with another equation, based on serum creatinine (Schwartz formula) to estimate GFR in children.

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.

Monitoring of kidney function in HIV-positive patients

HIV-positive patients are at increased risk of developing chronic kidney disease. Although guidelines recommend regular monitoring of renal function in individuals living with HIV, the optimal frequency remains to be defined. In this review, we discuss the renal syndromes that may be identified at an earlier stage via routine assessment of kidney function, and provide guidance in terms of the frequency of monitoring, the most useful tests to perform, and their clinical significance. Specifically, we address whether annual monitoring of kidney function is appropriate for the majority of HIV-positive patients.

Cystatin C- and creatinine-based equations in the assessment of renal function in HIV-positive patients prior to commencing Highly Active Antiretroviral Therapy

BACKGROUND

We evaluated the accuracy and precision of creatinine- and cystatin C-based prediction equations for estimating glomerular filtration rate compared to measured glomerular filtration rate in an antiretroviral-naive human immunodeficiency virus population.

METHODS

The study population consisted of 100 treatment-naive HIV patients. Glomerular filtration rate was estimated using the Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, as well as cystatin C-based equations (CKD-EPIcystatin C, cystatin Cvan Deventer and CKD-EPIcombined)) compared to (51)Cr-EDTA plasma clearance-measured glomerular filtration rate. We calculated percentage bias, standard deviation of the differences, accuracy within 15 and 30% of measured glomerular filtration rate and sensitivity and specificity for predicting measured glomerular filtration rate <60 mL/min/1.73 m(2).

RESULTS

Bias for all estimating glomerular filtration rate equations ranged from -9.4% to 38.4%. The CKD-EPIcombined without ethnicity correction factor equation had the least bias, 2.9% (-2.9 to 8.8). Bias was higher for the Modification of Diet in Renal Disease and CKD-EPI equation with the African-American ethnicity factor (38.4 and 33.7%) than without (14.2 and 15.3%). Standard deviation of the differences ranged from 29.2% (CKD-EPIcombined without ethnicity factor) to 54.0% (Modification of Diet in Renal Disease with ethnicity factor). Accuracy within 30% of measured glomerular filtration rate ranged from 78% for CKD-EPIcombined without ethnicity factor to 56.7% for the Cockcroft-Gault equation. Sensitivity for creatinine-based equations was less than 50% and for the CKD-EPIcystatin C equation was 75%.

CONCLUSION

Sensitivity of creatinine-based equations for predicting glomerular filtration rate was poor in this group of patients. The CKD-EPIcombined equation performed better than creatinine-based equations.

Applicability of estimating glomerular filtration rate equations in pediatric patients: comparison with a measured glomerular filtration rate by iohexol clearance

Estimating glomerular filtration rate (eGFR) has become popular in clinical medicine as an alternative to measured GFR (mGFR), but there are few studies comparing them in clinical practice. We determined mGFR by iohexol clearance in 81 consecutive children in routine practice and calculated eGFR from 14 standard equations using serum creatinine, cystatin C, and urea nitrogen that were collected at the time of the mGFR procedure. Nonparametric Wilcoxon test, Spearman correlation, Bland-Altman analysis, bias (median difference), and accuracy (P15, P30) were used to compare mGFR with eGFR. For the entire study group, the mGFR was 77.9 ± 38.8 mL/min/1.73 m(2). Eight of the 14 estimating equations demonstrated values without a significant difference from the mGFR value and demonstrated a lower bias in Bland-Altman analysis. Three of these 8 equations based on a combination of creatinine and cystatin C (Schwartz et al. New equations to estimate GFR in children with CKD. J Am Soc Nephrol 2009;20:629-37; Schwartz et al. Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C. Kidney Int 2012;82:445-53; Chehade et al. New combined serum creatinine and cystatin C quadratic formula for GFR assessment in children. Clin J Am Soc Nephrol 2014;9:54-63) had the highest accuracy with approximately 60% of P15 and 80% of P30. In 10 patients with a single kidney, 7 with kidney transplant, and 11 additional children with short stature, values of the 3 equations had low bias and no significant difference when compared with mGFR. In conclusion, the 3 equations that used cystatin C, creatinine, and growth parameters performed in a superior manner over univariate equations based on either creatinine or cystatin C and also had good applicability in specific pediatric patients with single kidneys, those with a kidney transplant, and short stature. Thus, we suggest that eGFR calculations in pediatric clinical practice use only a multivariate equation.

Association of urine α1-microglobulin with kidney function decline and mortality in HIV-infected women

BACKGROUND AND OBJECTIVES

Despite advances in therapy, HIV-infected individuals remain at higher risk for kidney dysfunction than uninfected individuals. It was hypothesized that urine levels of α1-microglobulin, a biomarker of proximal tubular dysfunction, would predict kidney function decline and mortality risk in HIV-infected and uninfected women.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In the Women's Interagency HIV Study, urine α1-microglobulin and creatinine concentrations were measured in 903 HIV-infected and 287 uninfected women using stored urine from 1999 to 2000, when prevalence of tenofovir use was <1%. Participants were categorized into three categories by level of α1-microglobulin-to-creatinine ratio, and associations with kidney decline and all-cause mortality over 8 years were evaluated.

RESULTS

Urine α1-microglobulin was detectable in 60% of HIV-infected and 40% of uninfected women (P<0.001). Among HIV-infected women, there were 177 (22%), 61 (7%), and 128 (14%) patients with incident CKD, with 10% annual eGFR decline, and who died, respectively. Compared with HIV-infected women in the lowest α1-microglobulin category, HIV-infected women in the highest α1-microglobulin category had a 2.1-fold risk of incident CKD (95% confidence interval, 1.3 to 3.4), 2.7-fold risk of 10% annual eGFR decline (95% confidence interval, 1.2 to 5.9), and 1.6-fold mortality risk (95% confidence interval, 1.0 to 2.6) in models adjusting for kidney risk factors, baseline eGFR, and albuminuria. Among uninfected women, the highest α1-microglobulin category was associated with 3% (relative risk, 2.2; 95% confidence interval, 1.4 to 3.5) and 5% (relative risk, 2.2; 95% confidence interval, 1.1 to 4.3) annual eGFR decline relative to the lowest α1-microglobulin category.

CONCLUSIONS

Proximal tubular dysfunction, indicated by urine α1-microglobulin, was independently associated with kidney function decline in HIV-infected and uninfected women and mortality risk among HIV-infected women.

The association of adiposity with kidney function decline among HIV-infected adults: findings from the Fat Redistribution and Metabolic Changes in HIV Infection (FRAM) study

OBJECTIVES

The aim of the study was to investigate the association of adiposity with longitudinal kidney function change in 544 HIV-infected persons in the Study of Fat Redistribution and Metabolic Change in HIV infection (FRAM) cohort over 5 years of follow-up.

METHODS

The regional distribution of muscle and adipose tissue was quantified by whole-body magnetic resonance imaging (MRI), and total adiponectin and leptin levels were measured in serum. Kidney function was assessed using the estimated glomerular filtration rate from serum cystatin C (eGFRCys), obtained at baseline and follow-up. Rapid kidney function decline was defined as annual loss of eGFRCys ≥ 3 mL/min/1.73 m(2) , and incident chronic kidney disease (CKD) was defined as eGFRCys <60 mL/min/1.73 m(2) . Multivariate regression analysis was adjusted for age, race, gender, glucose, antihypertensive use, serum albumin, baseline and change in HIV viral load.

RESULTS

At baseline, mean age was 43 years, mean eGFRCys was 86 mL/min/1.73 m(2) , and 21% of patients had albuminuria. The mean (± standard deviation) eGFRCys decline was -0.11 ± 4.87 mL/min/1.73 m(2) per year; 23% of participants had rapid kidney function decline, and 10% developed incident CKD. The lowest tertile of visceral adipose tissue and the highest tertile of adiponectin were both marginally associated with annual kidney function decline of -0.5 mL/min/1.73 m(2) each, but these associations were not statistically significant after adjustment. We found no statistically significant associations of MRI-measured regional adiposity or serum adipokines with rapid kidney function decline or incident CKD (all P-values>0.1 in adjusted models).

CONCLUSIONS

Contrary to findings in the general population, adiposity did not have a substantial association with longitudinal change in kidney function among HIV-infected persons.

Serum albumin and kidney function decline in HIV-infected women

BACKGROUND

Serum albumin concentrations are a strong predictor of mortality and cardiovascular disease in human immunodeficiency virus (HIV)-infected individuals. We studied the longitudinal associations between serum albumin levels and kidney function decline in a population of HIV-infected women.

STUDY DESIGN

Retrospective cohort analysis.

SETTING & PARTICIPANTS

Study participants were recruited from the Women's Interagency HIV Study (WIHS), a large observational study designed to understand risk factors for the progression of HIV infection in women living in urban communities. 908 participants had baseline assessment of kidney function and 2 follow-up measurements over an average of 8 years.

PREDICTOR

The primary predictor was serum albumin concentration.

OUTCOMES

We examined annual change in kidney function. Secondary outcomes included rapid kidney function decline and incident reduced estimated glomerular filtration rate (eGFR).

MEASUREMENTS

Kidney function decline was determined by cystatin C-based (eGFR(cys)) and creatinine-based eGFR (eGFR(cr)) at baseline and follow-up. Each model was adjusted for kidney disease and HIV-related risk factors using linear and relative risk regression.

RESULTS

After multivariate adjustment, each 0.5-g/dL decrement in baseline serum albumin concentration was associated with a 0.56-mL/min faster annual decline in eGFR(cys) (P < 0.001), which was attenuated only slightly to 0.55 mL/min/1.73 m(2) after adjustment for albuminuria. Results were similar whether using eGFR(cys) or eGFR(cr). In adjusted analyses, each 0.5-g/dL lower baseline serum albumin level was associated with a 1.71-fold greater risk of rapid kidney function decline (P < 0.001) and a 1.72-fold greater risk of incident reduced eGFR (P < 0.001).

LIMITATIONS

The cohort is composed of only female participants from urban communities within the United States.

CONCLUSIONS

Lower serum albumin levels were associated strongly with kidney function decline and incident reduced eGFRs in HIV-infected women independent of HIV disease status, body mass index, and albuminuria.

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.

The changing epidemiology of HIV-related chronic kidney disease in the era of antiretroviral therapy

The epidemiology of kidney disease in HIV-infected individuals has changed significantly since the introduction of combination antiretroviral therapy (cART) in the mid 1990s. HIV-associated nephropathy (HIVAN), an aggressive form of collapsing focal segmental glomerulosclerosis (FSGS) caused by direct HIV infection of the kidney in a genetically susceptible host, emerged early in the HIV epidemic as a leading cause of end-stage renal disease. With the widespread use of cART, HIVAN is increasingly rare in populations with access to care, and the spectrum of HIV-related chronic kidney disease now reflects the growing burden of comorbid disease in the aging HIV population. Nonetheless, available data suggest that both HIV infection and cART nephrotoxicity continue to contribute to the increased risk of chronic kidney disease in HIV-infected individuals in the United States and Europe. Despite the genetic susceptibility to HIVAN in individuals of West African descent, limited data are available to define the prevalence and spectrum of HIV-related kidney disease in sub-Saharan Africa, which is home to two-thirds of the world's HIV population. In this mini-review, we characterize the changing epidemiology of HIV-related chronic kidney disease in Western nations and in sub-Saharan Africa.

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.

Urinary biomarkers of kidney injury are associated with all-cause mortality in the Women's Interagency HIV Study (WIHS)

OBJECTIVES

Chronic kidney disease (CKD) is common in HIV-infected individuals, and is associated with mortality in both the HIV-infected and general populations. Urinary markers of tubular injury have been associated with future kidney disease risk, but associations with mortality are unknown.

METHODS

We evaluated the associations of urinary interleukin-18 (IL-18), liver fatty acid binding protein (L-FABP), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and the albumin-to-creatinine ratio (ACR) with 10-year, all-cause death in 908 HIV-infected women. Serum cystatin C was used to estimate the glomerular filtration rate (eGFRcys).

RESULTS

There were 201 deaths during 9269 person-years of follow-up. After demographic adjustment, compared with the lowest tertile, the highest tertiles of IL-18 [hazard ratio (HR) 2.54; 95% confidence interval (CI) 1.75-3.68], KIM-1 (HR 2.04; 95% CI 1.44-2.89), NGAL (HR 1.50; 95% CI 1.05-2.14) and ACR (HR 1.63; 95% CI 1.13-2.36) were associated with higher mortality. After multivariable adjustment including adjustment for eGFRcys, only the highest tertiles of IL-18 (HR 1.88; 95% CI 1.29-2.74) and ACR (HR 1.46; 95% CI 1.01-2.12) remained independently associated with mortality. Findings for KIM-1 were borderline (HR 1.41; 95% CI 0.99-2.02). We found a J-shaped association between L-FABP and mortality. Compared with persons in the lowest tertile, the HR for the middle tertile of L-FABP was 0.67 (95% CI 0.46-0.98) after adjustment. Associations were stronger when IL-18, ACR and L-FABP were simultaneously included in models.

CONCLUSIONS

Among HIV-infected women, some urinary markers of tubular injury are associated with mortality risk, independently of eGFRcys and ACR. These markers represent potential tools with which to identify early kidney injury in persons with HIV infection.

Does HIV infection promote early kidney injury in women?

BACKGROUND

In HIV-infected women, urine concentrations of novel tubulointerstitial injury markers, interleukin-18 (IL-18) and kidney injury marker-1 (KIM-1), are associated with kidney function decline and all-cause mortality. We hypothesized that HIV-infected individuals with preserved kidney filtration function would have more extensive kidney injury, as determined by urine injury markers, compared to the uninfected controls, and that risk factors for tubulointerstitial injury would differ from risk factors for albuminuria.

METHODS

In this cross-sectional study, we compared urine concentrations of IL-18, KIM-1 and albumin-to-creatinine ratio (ACR) in 908 HIV-infected and 289 HIV-uninfected women enrolled in the Women's Interagency HIV Study, utilizing stored urine specimens from visits between 1999 and 2000.

RESULTS

After multivariate-adjusted linear regression analysis, mean urine concentrations were higher in HIV-infected individuals by 38% for IL-18 (P<0.0001), 12% for KIM-1 (P=0.081) and 47% for ACR (P<0.0001). Higher HIV RNA level (15% per 10-fold increase; P<0.0001), lower CD4(+) lymphocyte count (8% per doubling; P=0.0025), HCV infection (30%; P=0.00018) and lower high-density lipoprotein (5% per 10 mg/dl; P=0.0024) were each associated with higher IL-18 concentrations. In contrast, hypertension (81%; P<0.0001) and diabetes (47%; P=0.018) were among the strongest predictors of higher ACR, though HIV RNA level (15% per 10-fold increase; P=0.0004) was also associated with higher ACR.

CONCLUSIONS

HIV-infected women had more extensive tubulointerstitial and glomerular injury than uninfected women, but the associated factors differed among the urine biomarkers. Combinations of urinary biomarkers should be investigated to further characterize early kidney injury in HIV-infected women.