Optimising the accuracy of blood pressure monitoring in chronic kidney disease: the utility of BpTRU

The Prognostic Role of Automated Office Blood Pressure Measurement in Hypertensive Patients with Chronic Kidney Disease

BACKGROUND

The aim of this study was to evaluate the prognostic value of automated office blood pressure (AOBP) measurement in patients with hypertension and chronic kidney disease (CKD) stage 3-5 not on dialysis.

METHODS

At baseline, 140 patients were recruited, and blood pressure (BP) measurements with 3 different methods, namely, office blood pressure (OBP), AOBP, and ambulatory blood pressure measurement (ABPM), were recorded. All patients were prospectively followed for a median period of 3.4 years. The primary outcome of this study was a composite outcome of cardiovascular (CV) events (both fatal and nonfatal) or a doubling of serum creatine or progression to end-stage kidney disease (ESKD), whichever occurred first.

RESULTS

At baseline, the median age of patients was 65.2 years; 36.4% had diabetes; 21.4% had a history of CV disease; the mean of estimated glomerular filtration rate (eGFR) was 33 mL/min/1.73 m²; and the means of OBP, AOBP, and daytime ABPM were 151/84 mm Hg, 134/77 mm Hg, and 132/77 mm Hg, respectively. During the follow-up, 18 patients had a CV event, and 37 patients had a renal event. In the univariate cox regression analysis, systolic AOBP was found to be predictive of the primary outcome (HR per 1 mm Hg increase in BP, 1.019, 95% CI 1.003-1.035), and after adjustment for eGFR, smoking status, diabetes, and a history of CV disease and systolic and diastolic AOBP were also found to be predictive of the primary outcome (HR per 1 mm Hg increase in BP, 1.017, 95% CI 1.002-1.032 and 1.033, 95% CI 1.009-1.058, respectively).

CONCLUSIONS

In patients with CKD, AOBP appears to be prognostic of CV risk or risk for kidney disease progression and could, therefore, be considered a reliable means for recording BP in the office setting.

Hypertension in Chronic Kidney Disease: An Update on Diagnosis and Management

Hypertension (HTN) and chronic kidney disease (CKD) are pathophysiologic states that are intimately related, such that long-term HTN can lead to poor kidney function, and renal function decline can lead to worsening blood pressure (BP) control. HTN in CKD is caused by an interplay of factors, including salt and water retention, with extracellular volume expansion, sympathetic nervous system overactivity, renin-angiotensin-aldosterone system activation, and endothelial dysfunction. BP variability in the CKD population is significant, however, and thus requires close monitoring for appropriate management. With accumulating evidence, the diagnosis as well as management of HTN in CKD has been evolving in the last decade. In this comprehensive review based on current evidence and recommendations, we summarize the basics of pathophysiology, BP variability, diagnosis, and management of HTN in CKD with an emphasis on special populations with CKD.

Acute Hemodynamic Responses to Three Types of Hamstrings Stretching in Senior Athletes

Although stretching is recommended for fitness and health, there is little research on the effects of different stretching routines on hemodynamic responses of senior adults. It is not clear whether stretching can be considered an aerobic exercise stimulus or may be contraindicated for the elderly. The purpose of this study was to compare the effect of three stretching techniques; contract/relax proprioceptive neuromuscular facilitation (PNF), passive straight-leg raise (SLR), and static sit-and-reach (SR) on heart rate (HR) and blood pressure (BP) in senior athletes (119 participants: 65.6 ± 7.6 yrs.). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and HR measurements were taken at baseline (after 5-minutes in a supine position), 45 and 90-seconds, during the stretch, and 2-minutes after stretching. Within each stretching group, (SLR, PNF, and SR) DBP, MAP and HR at pre-test and 2-min post-stretch were lower than at 45-s and 90-s during the stretch. SLR induced smaller increases in DBP and MAP than PNF and SR, whereas PNF elicited lower HR responses than SR. In conclusion, trained senior adult athletes experienced small to moderate magnitude increases of hemodynamic responses with SLR, SR and PNF stretching, which recovered to baseline values within 2-min after stretching. Furthermore, the passive SLR induced smaller increases in BP than PNF and SR, while PNF elicited lower HR responses than SR. These increases in hemodynamic responses (HR and BP) were not of a magnitude to be clinically significant, provide an aerobic exercise stimulus or warrant concerns for most senior athletes.

Unattended automated office blood pressure in living donor kidney transplant recipients

PURPOSE

Hypertension is common in kidney transplant recipients (KTRs). For the evaluation of blood pressure (BP), 24-h ambulatory BP measurements (ABPM) are considered superior to usual office measurements but are also resource demanding and troublesome to many patients. We therefore evaluated the use of unattended automated office BP (AOBP) during the first year following living donor kidney transplantation and compared AOBP with ABPM as obtained 12 months after transplantation.

MATERIALS AND METHODS

Data were retrieved from a cohort of 57 KTRs (mean age 45 ± 14 years, 75% males) who all received kidneys from living donors and had a good graft function (estimated glomerular filtration rate (eGFR) 52 ± 16 ml/min/1.73 m² at 12 months). Unattended AOBP was measured at each visit to the outpatient clinic using the BpTru® device, while ABPM was obtained by Spacelabs® equipment before and 12 months after transplantation.

RESULTS

AOBP remained stable from month 2 (130.2 ± 10.8/82.2 ± 7.8 mmHg) to month 12 (129.0 ± 12.8/83.1 ± 9.6 mmHg) post-transplantation. At 12 months follow-up, ambulatory daytime systolic BP was slightly higher than AOBP (132.7 ± 10.7 vs. 129.4 ± 12.2 mmHg, p = 0.04), while diastolic BP was similar (82.7 ± 7.7 vs. 82.0 ± 10.2 mmHg). Using Bland-Altman plots, 95% limits of agreements were -17.9 to 24.5 mmHg for systolic and -16.5 to 15.1 mmHg for diastolic BP. When considering a target BP of ≤130/<80 mmHg, 62% had sustained hypertension, 9% white coat hypertension and 11% masked hypertension. Using multiple linear regression analysis, only urine albumin-creatinine ratio tended to predict a higher systolic AOBP (p = 0.07).

CONCLUSION

In a cohort of stable living donor KTRs, mean values of unattended AOBP using BpTru® are comparable to daytime ABPM with a misclassification rate of approximately 20%.

Oxidative stress links periodontal inflammation and renal function

Aims

Patients with chronic kidney disease (CKD) are also susceptible to periodontitis. The causal link between periodontitis and CKD may be mediated via systemic inflammation/oxidative stress. Using structural equation modelling (SEM), this cross‐sectional study aimed to explore the causal relationship between periodontal inflammation (PI) and renal function.

Materials and methods

Baseline data on 770 patients with stage 3–5 (pre‐dialysis) CKD from an ongoing cohort study were used. Detailed, bioclinical data on PI and renal function, as well as potential confounders and mediators of the relationship between the two, were collected. SEMs of increasing complexity were created to test the causal assumption that PI affects renal function and vice versa.

Results

Structural equation modelling confirmed the assumption that PI and renal function are causally linked, mediated by systemic oxidative stress. The magnitude of this effect was such that a 10% increase in PI resulted in a 3.0% decrease in renal function and a 10% decrease in renal function resulted in a 25% increase in PI.

Conclusions

Periodontal inflammation represents an occult source of oxidative stress in patients with CKD. Further clinical studies are needed to confirm whether periodontal therapy, as a non‐pharmacological approach to reducing systemic inflammatory/oxidative stress burden, can improve outcomes in CKD.

Comparison of self- and nurse-measured office blood pressure in patients with chronic kidney disease

OBJECTIVE

As blood pressure (BP) control is very important in chronic kidney disease (CKD), we investigated how office BP is influenced by the measurement circumstances and compared nonautomated self- and nurse-measured BP values.

MATERIALS AND METHODS

Two hundred stage 1-5 CKD patients with scheduled visits to an outpatient clinic were randomized to either self-measured office BP (SMOBP) followed by nurse-measured office BP (NMOBP) or NMOBP followed by SMOBP. The participants had been educated to perform the self-measurement in at least one previous visit. The SMOBP and NMOBP measurement series both consisted of three recordings, and the means of the last two recordings during SMOBP and NMOBP were compared for the 174 (mean age 52.5 years) with complete BP data.

RESULTS

SMOBP and NMOBP showed similar systolic (135.3 ± 16.6 vs 136.4 ± 17.4 mmHg, Δ = 1.1 mmHg, P = 0.13) and diastolic (81.5 ± 10.2 vs 82.2 ± 10.4 mmHg, Δ = 0.6 mmHg, P = 0.09) values. The change in BP from the first to the third recording was not different for SMOBP and NMOBP. In 17 patients, systolic SMOBP was ≥10 mmHg higher than NMOBP and in 28 patients systolic NMOBP exceeded SMOBP by ≥10 mmHg. The difference between systolic SMOBP and NMOBP was independent of CKD stage and the number of medications, but significantly more pronounced in patients above 60 years.

CONCLUSION

In a population of CKD patients, there is no clinically relevant difference in SMOBP and NMOBP when recorded at the same visit. However, in 25% of the patients, systolic BP differs ≥10 mmHg between the two measurement modalities.

Association between urinary free light chains and progression to end stage renal disease in chronic kidney disease

Background

Patients with chronic kidney disease (CKD) are at an increased risk of developing end-stage renal disease (ESRD). We assessed for the first time whether urinary free light chains (FLC) are independently associated with risk of ESRD in patients with CKD, and whether they offer incremental value in risk stratification.

Materials and methods

We measured urinary FLCs in 556 patients with CKD from a prospective cohort study. The association between urinary kappa/creatinine (KCR) and lambda/creatinine (LCR) ratios and development of ESRD was assessed by competing-risks regression (to account for the competing risk of death). The change in C-statistic and integrated discrimination improvement were used to assess the incremental value of adding KCR or LCR to the Kidney Failure Risk Equation (KFRE).

Results

136 participants developed ESRD during a median follow-up time of 51 months. Significant associations between KCR and LCR and risk of ESRD became non-significant after adjustment for estimated glomerular filtration rate (eGFR) and albumin/creatinine ratio (ACR), although having a KCR or LCR >75^th centile remained independently associated with risk of ESRD. Neither KCR nor LCR as continuous or categorical variables provided incremental value when added to the KFRE for estimating risk of ESRD at two years.

Conclusions

Urinary FLCs have an association with progression to ESRD in patients with CKD which appears to be explained to a degree by their correlation with eGFR and ACR. Levels above the 75^th centile do have an independent association with ESRD, but do not improve upon a current model for risk stratification.

Clinical Implications of Different Blood Pressure Measurement Techniques

PURPOSE OF REVIEW

The appropriate treatment targets for individuals with elevated blood pressure (BP) have received increased attention in light of recent clinical trial results. However, it is well known that the method used to measure BP can have a significant impact on the observed BP. In this review, we summarize the existing literature on the impact of BP measurement technique on observed BP readings.

RECENT FINDINGS

Manual BPs obtained in-clinic routinely differ from those obtained using automated devices. Further, clinic-based readings (either manual or automated) typically correlate poorly with readings from ambulatory BP monitoring or home-based devices. However, few studies utilize randomization or sound experimental design to explore differences in BP readings by method or technique. While numerous studies report differences in BP by method, most lack statistical rigor and therefore provide limited insight into the true effect of technique on BP measurements.

Urinary endotrophin predicts disease progression in patients with chronic kidney disease

Renal fibrosis is the central pathogenic process in progression of chronic kidney disease (CKD). Collagen type VI (COL VI) is upregulated in renal fibrosis. Endotrophin is released from COL VI and promotes pleiotropic pro-fibrotic effects. Kidney disease severity varies considerably and accurate information regarding CKD progression may improve clinical decisions. We tested the hypothesis that urinary endotrophin derived during COL VI deposition in fibrotic human kidneys is a marker for progression of CKD in the Renal Impairment in Secondary Care (RIISC) cohort, a prospective observational study of 499 CKD patients. Endotrophin localised to areas of increased COL VI deposition in fibrotic kidneys but was not present in histologically normal kidneys. The third and fourth quartiles of urinary endotrophin:creatinine ratio (ECR) were independently associated with one-year disease progression after adjustment for traditional risk factors (OR (95%CI) 3.68 (1.06–12.83) and 8.65 (2.46–30.49), respectively). Addition of ECR quartiles to the model for disease progression increased prediction as seen by an increase in category-free net reclassification improvement (0.45, 95% CI 0.16–0.74, p = 0.002) and integrated discrimination improvement (0.04, 95% CI 0.02–0.06, p < 0.001). ECR was associated with development of end-stage renal disease (ESRD). It is concluded that ECR predicts disease progression of CKD patients.

Quality improvement project for managing elevated blood pressure in a primary care setting

Elevated blood pressure (BP) and prehypertension increase the risk of cardiovascular diseases, a national health concern. This article presents a quality improvement project implemented within a primary care setting that aimed at lowering cardiovascular risk by improving the identification, treatment, and follow-up of patients with elevated BP. This project was designed and implemented to address the identified deficiencies contributing to poor identification and follow-up of patients with elevated BP. The intervention was multi-pronged and comprised a staff educational program, introduction of a new method for measuring BP using the BpTRU™ device, and patient educational intervention. A significant improvement in staff BP knowledge scores was achieved following the intervention (p<0.05). Patient participants also exhibited a significant improvement in post-intervention BP measurements (p<0.05). This project showed that the implementation of a quality improvement project in a primary care setting can lead to significant improvements in staff BP knowledge and patient BP readings. However, future research in this area is required to determine whether particular lifestyle changes are directly associated with the reduction in BP.

Serum endotrophin, a type VI collagen cleavage product, is associated with increased mortality in chronic kidney disease

Background

Patients with chronic kidney disease (CKD) are at increased risk of end-stage renal disease (ESRD) and early mortality. The underlying pathophysiological processes are not entirely understood but may include dysregulation of extracellular matrix formation with accelerated systemic and renal fibrosis. We assessed the relationship between endotrophin (ETP), a marker of collagen type VI formation, and adverse outcomes in a cohort of patients with CKD.

Methods

We measured serum ETP levels in 500 patients from the Renal Impairment in Secondary Care (RIISC) study, a prospective observational study of patients with high-risk CKD. Patients were followed up until death or progression to ESRD. Cox regression analysis was used to assess the relationship between ETP and risk of adverse outcomes.

Results

During a median follow-up time of 37 months, 104 participants progressed to ESRD and 66 died. ETP level was significantly associated with progression to ESRD (HR 1.79 [95% CI 1.59–2.02] per 10 ng/mL increase; HR 11.05 [4.98–24.52] for highest vs lowest quartile; both P<0.0001). ETP level was also significantly associated with mortality (HR 1.60 [1.35–1.89] per 10 ng/mL increase; HR 12.14 [4.26–34.54] for highest vs lowest quartile; both P<0.0001). After adjustment for confounding variables, ETP was no longer significantly associated with progression to ESRD but remained independently associated with mortality (HR 1.51 [1.07–2.12] per 10 ng/mL increase, P = 0.019).

Conclusions

Serum ETP level is independently associated with mortality in CKD. This study provides the basis for further exploratory work to establish whether collagen type VI formation is mechanistically involved in the increased mortality risk associated with CKD.

Are Automated Blood Pressure Monitors Comparable to Ambulatory Blood Pressure Monitors? A Systematic Review and Meta-analysis

Ambulatory blood pressure (BP) monitoring (ABPM) provides an accurate assessment of BP and cardiovascular risk. BpTRU (BpTRU Medical Devices Ltd, Coquitlam, British Columbia, Canada) and other automated oscillometric BP monitors (AOBPs) have been proposed to replace ABPM. A systematic review was carried out to determine the accuracy of AOBP measurement, compared with ABPM. A literature search was performed using MedLine, EMBASE and CINAHL databases until Oct 28, 2016. We selected all studies that included intraindividual comparisons between AOBP monitoring and ABPM. Study selection, demographic characteristics, and BP values including details of BP measurement techniques were abstracted in duplicate. Quantitative synthesis was performed to report the weighted mean difference between systolic and diastolic BP measured using the 2 methods. From the 859 nonduplicate citations from the search, 19 full-text articles were selected for the systematic review. The median sample size was 226 (range, 17-654). In the pooled analysis, the weighted mean difference between the 2 methods for systolic BP was -1.52 mm Hg (95% confidence interval [CI], -3.29 to 0.25 mm Hg; P = 0.09) and for diastolic BP was 0.33 mm Hg (95% CI, -0.97 to 1.64; P = 0.62). The study-level difference in means for systolic BP ranged from -9.7 to 9 mm Hg with significant heterogeneity (Cochran Q = 270; I² = 93.3; P < 0.001) and for diastolic BP ranged from -4 to 6 mm Hg with significant heterogeneity (Cochran Q = 382; I² = 95.3; P < 0.001). Because of the significant heterogeneity we believe that use of the AOBP should not replace awake ambulatory BP (ABPM) as the reference standard.

Health-Related Quality of Life Impacts Mortality but Not Progression to End-Stage Renal Disease in Pre-Dialysis Chronic Kidney Disease: A Prospective Observational Study

Background

Chronic kidney disease (CKD) is associated with reduced health-related quality of life (HRQL). However, the relationship between pre-dialysis CKD, HRQL and clinical outcomes, including mortality and progression to end-stage renal disease (ESRD) is unclear.

Methods

All 745 participants recruited into the Renal Impairment In Secondary Care study to end March 2014 were included. Demographic, clinical and laboratory data were collected at baseline including an assessment of HRQL using the Euroqol EQ-5D-3L. Health states were converted into an EQ-5D_index score using a set of weighted preferences specific to the UK population. Multivariable Cox proportional hazards regression and competing risk analyses were undertaken to evaluate the association of HRQL with progression to ESRD or all-cause mortality. Regression analyses were then performed to identify variables associated with the significant HRQL components.

Results

Median eGFR was 25.8 ml/min/1.73 m² (IQR 19.6–33.7ml/min) and median ACR was 33 mg/mmol (IQR 6.6–130.3 mg/mmol). Five hundred and fifty five participants (75.7%) reported problems with one or more EQ-5D domains. When adjusted for age, gender, comorbidity, eGFR and ACR, both reported problems with self-care [hazard ratio 2.542, 95% confidence interval 1.222–5.286, p = 0.013] and reduced EQ-5D_index score [hazard ratio 0.283, 95% confidence interval 0.099–0.810, p = 0.019] were significantly associated with an increase in all-cause mortality. Similar findings were observed for competing risk analyses. Reduced HRQL was not a risk factor for progression to ESRD in multivariable analyses.

Conclusions

Impaired HRQL is common in the pre-dialysis CKD population. Reduced HRQL, as demonstrated by problems with self-care or a lower EQ-5D_index score, is associated with a higher risk for death but not ESRD. Multiple factors influence these aspects of HRQL but renal function, as measured by eGFR and ACR, are not among them.

Serum tryptase concentration and progression to end-stage renal disease

BACKGROUND

Mast cell activation can lead to nonclassical activation of the Renin-Angiotensin-Aldosterone System. However, the relevance of this to human chronic kidney disease is unknown. We assessed the association between serum tryptase, a product of mast cell activation, and progression to end-stage renal disease or mortality in patients with advanced chronic kidney disease. We stratified patients by use of angiotensin-converting enzyme inhibitors/angiotensin receptor II blockers (ACEi/ARB).

MATERIALS AND METHODS

This was a prospective cohort study of 446 participants recruited into the Renal Impairment in Secondary Care study. Serum tryptase was measured at recruitment by sandwich immunoassay. Cox regression analysis was undertaken to determine variables associated with progression to end-stage renal disease or death.

RESULTS

Serum tryptase concentration was independently associated with progression to end-stage renal disease but not with death. In patients treated with ACEi or ARB, there was a strong independent association between higher tryptase concentrations and progression to end-stage renal disease; when compared to the lowest tertile, tryptase concentrations in the middle and highest tertiles had hazard ratios [HR] of 5·78 (95% confidence interval [CI] 1·19-28·03, P = 0·029) and 6·19 (95% CI 1·49-25·69, P = 0·012), respectively. The other independent risk factors for progression to end-stage renal disease were lower age, male gender, lower estimated glomerular filtration rate and higher urinary albumin creatinine ratio.

CONCLUSION

Elevated serum tryptase concentration is an independent prognostic factor for progression to end-stage renal disease in patients with chronic kidney disease who are receiving treatment with an ACEi or ARB.

Prevalence of pseudoresistant hypertension due to inaccurate blood pressure measurement

The prevalence of pseudoresistant hypertension (HTN) due to inaccurate BP measurement remains unknown. Triage BP measurements and measurements obtained at the same clinic visit by trained physicians were compared in consecutive adult patients referred for uncontrolled resistant HTN (RHTN). Triage BP measurements were taken by the clinic staff during normal intake procedures. BP measurements were obtained by trained physicians using the BpTRU (VSM Med Tech Ltd. Coquitlam, Canada) device. The prevalence of uncontrolled RHTN and differences in BP measurements were compared. Of 130 patients with uncontrolled RHTN, 33.1% (n = 43) were falsely identified as having uncontrolled RHTN based on triage BP measurements. The median (inter-quartile range) of differences in systolic BP between pseudoresistant and true resistant groups were 23 (17-33) mm Hg and 13 (6-21) mm Hg, respectively (P = .0001). The median (inter-quartile range) of differences in diastolic BP between the two groups were 12 (7-18) mm Hg and 8 (4-11) mm Hg, respectively (P = .001). Triage BP technique overestimated the prevalence of uncontrolled RHTN in approximately 33% of the patients emphasizing the importance of obtaining accurate BP measurements.

The natural history of, and risk factors for, progressive chronic kidney disease (CKD): the Renal Impairment in Secondary care (RIISC) study; rationale and protocol

BACKGROUND

Chronic kidney disease (CKD) affects up to 16% of the adult population and is associated with significant morbidity and mortality. People at highest risk from progressive CKD are defined by a sustained decline in estimated glomerular filtration rate (eGFR) and/or the presence of significant albuminuria/proteinuria and/or more advanced CKD. Accurate mapping of the bio-clinical determinants of this group will enable improved risk stratification and direct the development of better targeted management for people with CKD.

METHODS/DESIGN

The Renal Impairment In Secondary Care study is a prospective, observational cohort study, patients with CKD 4 and 5 or CKD 3 and either accelerated progression and/or proteinuria who are managed in secondary care are eligible to participate. Participants undergo a detailed bio-clinical assessment that includes measures of vascular health, periodontal health, quality of life and socio-economic status, clinical assessment and collection of samples for biomarker analysis. The assessments take place at baseline, and at six, 18, 36, 60 and 120 months; the outcomes of interest include cardiovascular events, progression to end stage kidney disease and death.

DISCUSSION

The determinants of progression of chronic kidney disease are not fully understood though there are a number of proposed risk factors for progression (both traditional and novel). This study will provide a detailed bio-clinical phenotype of patients with high-risk chronic kidney disease (high risk of both progression and cardiovascular events) and will repeatedly assess them over a prolonged follow up period. Recruitment commenced in Autumn 2010 and will provide many outputs that will add to the evidence base for progressive chronic kidney disease.