Association of blood pressure with decline in renal function and time until the start of renal replacement therapy in pre-dialysis patients: a cohort study

Validation of histopathological chronicity scores in native kidney biopsies using light microscopy and digital morphometry for predicting renal outcome

Quantitative assessment of chronicity changes in native kidney biopsies offer valuable insights in to disease prognosis, despite the strength of qualitative information. Yet, standardization and reproducibility remain challenging. The present study aims to assess and compare the prognostic utility and reproducibility of two chronicity scoring systems based on light microscopy and whole slide imaging with morphometry and also to evaluate the prognostic utility of structural measurements: cortical non-sclerotic glomerular (NSG) density and NSG area/volume. We designed a retrospective longitudinal study involving 101 adult and paediatric patients who underwent native kidney biopsies. Chronicity scoring was performed using two semi-quantitative methods: Method 1 (method proposed in PMID: 28314581) and Method 2 (method proposed in PMID: 32516862), under light microscopy as well as on whole-slide scanned images, and assessed for prognostic utility. Kidney-Failure-Risk-Equation (KFRE) was employed in combination with chronicity-scoring-methods and assessed for predictive capability. Interobserver reproducibility for the two chronicity methods was studied among three renal pathologists. Structural measurements were performed on whole-slide- scanned-images. Both the chronicity scoring methods significantly predicted decline in estimated glomerular filtration rate (eGFR) and persistent need for renal replacement therapy in follow-up. Method 1 combined with KFRE, outperformed Method 2 in predicting renal survival. Method 2 however showed higher interobserver reproducibility. Combined KFRE plus histopathological scoring methods showed better predictive accuracy. The study validates the precision of chronicity scoring using whole slide scanned images. The morphometric structural measurements showed significant correlations with follow-up eGFR, thereby providing supplementary prognostic information.

ACE Inhibitor Benefit to Kidney and Cardiovascular Outcomes for Patients with Non-Dialysis Chronic Kidney Disease Stages 3-5: A Network Meta-Analysis of Randomised Clinical Trials

Background

The advantages of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) in reducing risk of cardiovascular events (CVEs) and delaying end-stage kidney disease (ESKD) in patients with chronic kidney disease (CKD) is well-known. However, the efficacy and safety of these agents in non-dialysis CKD stages 3–5 patients are still a controversial issue.

Methods

Two investigators (Yaru Zhang and Dandan He) independently searched and identified relevant studies from MEDLINE (from 1950 to October 2018), EMBASE (from 1970 to October 2018), and the Cochrane Library database. Randomised clinical trials in non-dialysis CKD3–5 patients treated with renin-angiotensin system (RAS) inhibitors were included. We used standard criteria (Cochrane risk of bias tool) to assess the inherent risk of bias of trials. We calculated the odds ratio (OR) and 95% confidence interval (CI) for each outcome by random-effects model. A 2-sided p value < 0.05 was considered statistically significant, and all statistical analyses were performed using STATA, version 15.0. This network meta-analysis was undertaken by the frequency model.

Results

Forty-four randomised clinical trials with 42,319 patients were included in our network meta-analysis. ACEIs monotherapy significantly decreased the odds of kidney events (OR 0.54, 95% CI 0.41–0.73), cardiovascular events (OR 0.73, 95% CI 0.64–0.84), cardiovascular death (OR 0.73, 95% CI 0.63–0.86) and all-cause death (OR 0.77, 95% CI 0.66–0.91) when compared to placebo. According to the cumulative ranking area (SUCRA), ACEI monotherapy had the highest probabilities of their protective effects on outcomes of kidney events (SUCRA 93.3%), cardiovascular events (SUCRA 77.2%), cardiovascular death (SUCRA 86%), and all-cause death (SUCRA 94.1%), even if there were no significant differences between ACEIs and other antihypertensive drugs, including calcium channel blockers (CCBs), β-blockers and diuretics on above outcomes except for kidney events. ARB monotherapy and combination therapy of an ACEI plus an ARB showed no more advantage than CCBs, β-blockers and diuretics in all primary outcomes. In the subgroup of non-dialysis diabetic kidney disease patients, no drugs, including ACEIs or ARBs, significantly lowered the odds of cardiovascular events and all-cause death. However, ACEIs were still better than other antihypertensive drugs including ARBs in all-cause death but not ARBs in cardiovascular events according to the SUCRA. Only ARBs had significant differences in preventing the occurrence of kidney events compared with placebo (OR 0.82, 95% CI 0.72–0.95). Both ACEI/ARB monotherapy and combination therapy had higher odds of hyperkalaemia. ACEIs had 3.81 times higher odds than CCBs (95% CI 1.58–9.20), ARBs had 2.08–5.10 times higher odds than placebo and CCBs and combination therapy of an ACEI and an ARB had 4.80–24.5 times higher odds than all other treatments. Compared with placebo, CCBs and β blockers, ACEI therapy significantly increased the odds of cough (OR 2.90, 95% CI 1.76–4.77; OR 8.21, 95% CI 3.13–21.54 and OR 1.80, 95% CI 1.08–3.00). There were no statistical differences in hypotension among all comparisons except ACEIs versus placebo.

Conclusions

Although ACEIs increased the odds of hyperkalaemia, cough and hypotension, they were still superior to ARBs and other antihypertensive drugs and had the highest benefits for the prevention of kidney events, cardiovascular outcomes, cardiovascular death and all-cause mortality in non-dialysis CKD3–5 patients. In patients with advanced diabetic kidney disease, ACEIs were superior to ARBs in lowering risk of all-cause death but not in kidney events and cardiovascular events.

Electronic supplementary material

The online version of this article (10.1007/s40265-020-01290-3) contains supplementary material, which is available to authorized users.

Pitfalls of linear regression for estimating slopes over time and how to avoid them by using linear mixed-effects models

Clinical epidemiological studies often focus on investigating the underlying causes of disease. For instance, a nephrologist may be interested in the association between blood pressure and the development of chronic kidney disease (CKD). However, instead of focusing on the mere occurrence of CKD, the decline of kidney function over time might be the outcome of interest. For examining this kidney function trajectory, patients are typically followed over time with their kidney function estimated at several time points. During follow-up, some patients may drop out earlier than others and for different reasons. Furthermore, some patients may have greater kidney function at study entry or faster kidney function decline than others. Also, a substantial heterogeneity may exist in the number of kidney function estimates available for each patient. This heterogeneity with respect to kidney function, dropout and number of kidney function estimates is important to take into account when estimating kidney function trajectories. In general, two methods are used in the literature to estimate kidney function trajectories over time: linear regression to estimate individual slopes and the linear mixed-effects model (LMM), i.e. repeated measures analysis. Importantly, the linear regression method does not properly take into account the above-mentioned heterogeneity, whereas the LMM is able to retain all information and variability in the data. However, the underlying concepts, use and interpretation of LMMs are not always straightforward. Therefore we illustrate this using a clinical example and offer a framework of how to model and interpret the LMM.

Decline of kidney function during the pre-dialysis period in chronic kidney disease patients: a systematic review and meta-analysis

Purpose

Substantial heterogeneity exists in reported kidney function decline in pre-dialysis chronic kidney disease (CKD). By design, kidney function decline can be studied in CKD 3–5 cohorts or dialysis-based studies. In the latter, patients are selected based on the fact that they initiated dialysis, possibly leading to an overestimation of the true underlying kidney function decline in the pre-dialysis period. We performed a systematic review and meta-analysis to compare the kidney function decline during pre-dialysis in CKD stage 3–5 patients, in these two different study types.

Patients and methods

We searched PubMed, EMBASE, Web of Science and Cochrane to identify eligible studies reporting an estimated glomerular filtration rate (eGFR) decline (mL/min/1.73 m²) in adult pre-dialysis CKD patients. Random-effects meta-analysis was performed to obtain weighted mean annual eGFR decline.

Results

We included 60 studies (43 CKD 3–5 cohorts and 17 dialysis-based studies). The meta-analysis yielded a weighted annual mean (95% CI) eGFR decline during pre-dialysis of 2.4 (95% CI: 2.2, 2.6) mL/min/1.73 m² in CKD 3–5 cohorts compared to 8.5 (95% CI: 6.8, 10.1) in dialysis-based studies (difference 6.0 [95% CI: 4.8, 7.2]).

Conclusion

To conclude, dialysis-based studies report faster mean annual eGFR decline during pre-dialysis than CKD 3–5 cohorts. Thus, eGFR decline data from CKD 3–5 cohorts should be used to guide clinical decision making in CKD patients and for power calculations in randomized controlled trials with CKD progression during pre-dialysis as the outcome.

Longitudinal Blood Pressure in Late-Stage Chronic Kidney Disease and the Risk of End-Stage Kidney Disease or Mortality (Best Blood Pressure in Chronic Kidney Disease Study)

Whether different methods of quantitating blood pressure (BP) in late chronic kidney disease better mimic pathophysiological processes and clinical outcomes remains unclear. In a retrospective study, we determined the association of BP with end-stage kidney disease (ESKD) and all-cause mortality with BP modeled at baseline versus longitudinally with time-varying Cox models as (1) current (most recent) clinic visit, (2) lag (visit immediately preceding the current), (3) cumulative (average of previous measurements), and (4) change from baseline to the most recent. Among 1203 (6913 visits) study patients, the mean age and baseline estimated glomerular filtration rate were 66 and 18 mL·min −1 ·1.73 m −2 ), and 40% were female. Patients had a mean of 6.7 BP measurements, 540 (44.8%) reached ESKD, and 141 (11.7%) died. For systolic BP >160, current (hazard ratio [HR], 1.67), cumulative (HR, 1.58), and a rise to >160 from baseline 120 to 160 (HR, 1.60) were associated with ESKD. Similarly, diastolic BP >85 was associated with ESKD when modeled as current (HR, 1.47), lag (HR, 1.63), cumulative (HR, 2.15), or change from baseline (rise to >85 from a baseline of 60–85; HR, 1.62). Both low SBP (<120), when modeled as current (HR, 1.59), cumulative exposure (HR, 1.76), persistently <120 (HR, 2.28), and high SBP (>140), when modeled as cumulative exposure, were associated with all-cause mortality. For diastolic BP, only cumulative >85 was significantly associated with mortality (HR, 2.75). Thus, in late-stage chronic kidney disease, persistently high or rises in systolic BP or diastolic BP are associated with risk of ESKD, whereas baseline BP measures did not convey information on risk.

Time-Varying Association of Individual BP Components with eGFR in Late-Stage CKD

BACKGROUND AND OBJECTIVES

The association of individual BP components with changes in eGFR in patients with late-stage CKD is unknown. The objectives of our study were to examine the associations of systolic BP, diastolic BP, and pulse pressure with continuous temporal changes in eGFR and an eGFR decline ≥30% in late-stage CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a retrospective cohort study (2010-2015) of patients with CKD in a multidisciplinary CKD clinic with an eGFR≤30. The associations of repeat measures of BP (systolic BP, diastolic BP, and pulse pressure) with eGFR were examined using general linear mixed models. The associations of BP components and eGFR decline ≥30% were examined with time-varying Cox models.

RESULTS

In total, 1203 patients were followed for a median of 548 days (interquartile range, 292-913), with an average of 6.7 visits and BP measures per patient. Mean baseline systolic BP, diastolic BP, pulse pressure, and eGFR were 139.2 mmHg, 73.2 mmHg, 64.9 mmHg, and 16.8 ml/min, respectively. Systolic BP and diastolic BP measures over time were statistically significantly associated with changes in eGFR (P<0.001), whereas pulse pressure was not. Patients with extremes of systolic BP (<105 or >170) and high diastolic BP (>90) measures were at a higher risk of GFR decline ≥30% (systolic BP <105: hazard ratio, 1.51; 95% confidence interval, 0.98 to 2.34; systolic BP >170: hazard ratio, 1.62; 95% confidence interval, 1.05 to 2.49; referent systolic BP =121-130; diastolic BP =81-90: hazard ratio, 1.40; 95% confidence interval, 0.99 to 1.86; diastolic BP >90: hazard ratio, 1.83; 95% confidence interval, 1.21 to 2.77; referent diastolic BP =61-70). The findings were consistent after multiple sensitivity analyses. Pulse pressure was not significantly associated with risk of eGFR decline.

CONCLUSIONS

In patients referred to a multidisciplinary care clinic with late-stage CKD, only extremes of systolic BP and elevations of diastolic BP were associated with eGFR decline.

Effect of glomerular filtration rate at dialysis initiation on survival in patients with advanced chronic kidney disease: what is the effect of lead-time bias?

PURPOSE

Current clinical guidelines recommend to initiate dialysis in the presence of symptoms or signs attributable to kidney failure, often with a glomerular filtration rate (GFR) of 5-10 mL/min/1.73 m2. Little evidence exists about the optimal kidney function to start dialysis. Thus far, most observational studies have been limited by lead-time bias. Only a few studies have accounted for lead-time bias, and showed contradictory results. We examined the effect of GFR at dialysis initiation on survival in chronic kidney disease patients, and the role of lead-time bias therein. We used both kidney function based on 24-hour urine collection (measured GFR [mGFR]) and estimated GFR (eGFR).

MATERIALS AND METHODS

A total of 1,143 patients with eGFR data at dialysis initiation and 852 patients with mGFR data were included from the NECOSAD cohort. Cox regression was used to adjust for potential confounders. To examine the effect of lead-time bias, survival was counted from the time of dialysis initiation or from a common starting point (GFR 20 mL/min/1.73 m2), using linear interpolation models.

RESULTS

Without lead-time correction, no difference between early and late starters was present based on eGFR (hazard ratio [HR] 1.03, 95% confidence interval [CI] 0.81-1.3). However, after lead-time correction, early initiation showed a survival disadvantage (HR between 1.1 [95% CI 0.82-1.48] and 1.33 [95% CI 1.05-1.68]). Based on mGFR, the potential survival benefit for early starters without lead-time correction (HR 0.8, 95% CI 0.62-1.03) completely disappeared after lead-time correction (HR between 0.94 [95% CI 0.65-1.34] and 1.21 [95% CI 0.95-1.56]). Dialysis start time differed about a year between early and late initiation.

CONCLUSION

Lead-time bias is not only a methodological problem but also has clinical impact when assessing the optimal kidney function to start dialysis. Therefore, lead-time bias is extremely important to correct for. Taking account of lead-time bias, this controlled study showed that early dialysis initiation (eGFR >7.9, mGFR >6.6 mL/min/1.73 m2) was not associated with an improvement in survival. Based on kidney function, this study suggests that in some patients, dialysis could be started even later than an eGFR <5.7 and mGFR <4.3 mL/min/1.73 m2.

Long-Term Visit-to-Visit Blood Pressure Variability and Renal Function Decline in Patients With Hypertension Over 15 Years

BACKGROUND

Visit-to-visit variability of systolic blood pressure (SBP) has been shown to contribute to cardiovascular events and all-cause mortality. However, little is known about its long-term effect on renal function. We aim to examine the relationship between visit-to-visit blood pressure variability (BPV) and decline in renal function in patients with hypertension and to determine the level of systolic BPV that is associated with significant renal function decline.

METHODS AND RESULTS

This is a 15-year retrospective cohort study of 825 hypertensive patients. Blood pressure readings every 3 months were retrieved from the 15 years of clinic visits. We used SD and coefficient of variation as a measure of systolic BPV. Serum creatinine was captured and estimated glomerular filtration rate was calculated at baseline, 5, 10, and 15 years. The mean SD of SBP was 14.2±3.1 mm Hg and coefficient of variation of SBP was 10.2±2%. Mean for estimated glomerular filtration rate slope was -1.0±1.5 mL/min per 1.73 m2 per year. There was a significant relationship between BPV and slope of estimated glomerular filtration rate (SD: r=-0.16, P<0.001; coefficient of variation: r=-0.14, P<0.001, Pearson's correlation). BPV of SBP for each individual was significantly associated with slope of estimated glomerular filtration rate after adjustment for mean SBP and other confounders. The cutoff values estimated by the receiver operating characteristic curve for the onset of chronic kidney disease for SD of SBP was 13.5 mm Hg and coefficient of variation of SBP was 9.74%.

CONCLUSIONS

Long-term visit-to-visit variability of SBP is an independent determinant of renal deterioration in patients with hypertension. Hence, every effort should be made to reduce BPV in order to slow down the decline of renal function.

Visit-to-visit variability of blood pressure and renal function decline in patients with diabetic chronic kidney disease

The authors previously reported that the visit-to-visit variability of blood pressure is correlated with renal function decline in nondiabetic chronic kidney disease. Little is known about the association between visit-to-visit variability and renal function decline in patients with diabetic chronic kidney disease. The authors retrospectively studied 69 patients with diabetic chronic kidney disease stage 3a, 3b, or 4. The standard deviation and coefficient of variation of blood pressure in 12 consecutive visits were defined as visit-to-visit variability of blood pressure. The median observation period was 32 months. In univariate correlation, the standard deviation and coefficient of variation of blood pressure were not significantly associated with the slope of estimated glomerular filtration rate. There was no significant association between the visit-to-visit variability of blood pressure and renal function decline in patients with diabetic chronic kidney disease, in contrast with our previous study of nondiabetic patients with chronic kidney disease.

Effect of erythropoiesis-stimulating agents on blood pressure in pre-dialysis patients

Introduction

Erythropoiesis-Stimulating Agents (ESA) are hypothesized to increase cardiovascular mortality in patients with chronic kidney disease. One of the proposed mechanisms is the elevation of blood pressure (BP) by ESA. Therefore, we aimed to determine whether the use of ESA was associated with antihypertensive treatment and higher BP.

Materials and Methods

In this cohort 502 incident pre-dialysis patients were included who started specialized pre-dialysis care in 25 clinics in the Netherlands. Data on medication including ESA use and dose, co-morbidities and BP were routinely collected every 6 months. Antihypertensive treatment and BP were compared for patients with and without ESA at baseline. Differences in antihypertensive medication and BP during pre-dialysis care were estimated with linear mixed models adjusted for age, sex, body mass index, cardiovascular disease, diabetes mellitus and estimated glomerular filtration rate.

Results

At baseline, 95.6% of patients with ESA were treated with antihypertensive medication and 73.1% of patients without ESA. No relevant difference in BP was found. During pre-dialysis care patients with ESA used 0.77 (95% CI 0.63;0.91) more classes of antihypertensive drugs. The adjusted difference in systolic blood pressure (SBP) was −0.3 (95% CI −2.7;2.0) mmHg and in diastolic blood pressure (DBP) was −1.0 (95% CI −2.1;0.3) mmHg for patients with ESA compared to patients without ESA. Adjusted SBP was 3.7 (95% CI −1.6;9.0) mmHg higher in patients with a high ESA dose compared to patients with a low ESA dose.

Conclusions

Our study confirms the hypertensive effect of ESA, since ESA treated patients received more antihypertensive agents. However, no relevant difference in BP was found between patients with and without ESA, thus the increase in BP seems to be controlled for by antihypertensive medication.

Association of blood pressure with the start of renal replacement therapy in elderly compared with young patients receiving predialysis care

BACKGROUND

In the growing elderly predialysis population, little is known about the effect of identified risk factors on the progression to end-stage renal disease. Therefore, we investigated the association of systolic (SBP) and diastolic blood pressure (DBP) with the start of renal replacement therapy (RRT), in elderly (≥65 years) compared with young (<65 years) predialysis patients.

METHODS

In the PREPARE-1 cohort, 547 incident predialysis patients, referred as part of the usual care to eight Dutch predialysis care outpatient clinics, were included (1999-2001) and followed until the start of dialysis, transplantation, death, or until 1 January 2008. The outcome was the start of RRT. All analyses were stratified for age; <65 years (young) and ≥65 years (elderly).

RESULTS

In young predialysis patients (n = 268) higher SBP (every 20 mm Hg increase) and high DBP (DBP ≥100 mm Hg compared with 80-89 mm Hg) were associated with a higher rate of starting RRT (adjusted hazard ratio (HR) (95% confidence interval) 1.21 (1.09;1.34) and 1.74 (1.16;2.62), respectively). However, in elderly predialysis patients (n = 240) only patients with SBP ≥180 mm Hg had an increased rate compared with patients with 140-159 mm Hg (adjusted HR 2.33 (1.41;3.87)). Furthermore, patients with DBP <70 or ≥100 mm Hg had an increased rate of starting RRT, independent of SBP, compared with patients with 80-89 mm Hg (fully adjusted HR 1.72 (1.01;2.94) and 2.05 (1.13;3.73), respectively).

CONCLUSIONS

The association of SBP and DBP with the start of RRT is different between elderly and young predialysis patients.

Impact of visit-to-visit variability of blood pressure on deterioration of renal function in patients with non-diabetic chronic kidney disease

An association between visit-to-visit variability (VVV) of blood pressure (BP) and renal damage was recently reported in a cross-sectional study. We aimed to clarify the longitudinal effect of VVV of BP on deterioration of renal function in patients with non-diabetic chronic kidney disease (CKD). We retrospectively studied 56 patients with non-diabetic CKD (stage 3 or 4) who visited our nephrology clinic between September 1994 and May 2011. VVV of BP was defined as the standard deviation and coefficient of variation (CV) of office BP measured at 12 consecutive visits. Main outcomes were the annual decline in the estimated glomerular filtration rate (eGFR) and the composite renal end point defined as a doubling of serum creatinine or the need for dialysis. The median observation period was 83 months. Standard deviation and CV of office systolic BP (SBP) were significantly associated with the slope of the eGFR after adjustments for confounders. The adjusted risk for composite renal end points more than doubled for each increment of 1-standard deviation of the standard deviation of office SBP (hazard ratio (HR) 2.20, P=0.001), and for each increment of 1-standard deviation of the CV of office SBP (HR 2.12, P=0.002). The present study demonstrated that the visit-to-visit variability of BP is an independent determinant of deterioration of renal function in patients with non-diabetic CKD.