Simon D.S. Fraser

Prevalence and associations of limited health literacy in chronic kidney disease: a systematic review

BACKGROUND Health literacy (HL) is important in chronic disease. This review aimed to evaluate the literature evidence on prevalence and associations of limited HL in chronic kidney disease (CKD). METHODS Seven databases were searched using terms for CKD and HL. Studies were included that ascertained the prevalence of limited HL using a validated tool in adults with CKD of any stage. The primary outcome was an objectively measured prevalence of limited HL in a population with CKD. The secondary outcome was associations of limited HL. Two reviewers assessed study inclusion and quality. Prevalence values were combined using a random-effect model to give overall prevalence. RESULTS Eighty-two studies were identified from searching, of which six met the inclusion criteria. The total number of people in all studies was 1405. Five studies were in dialysis or transplant populations, and all were from the USA. There was a significant heterogeneity in the prevalence of limited HL [9-32% (median 25%, inter-quartile range 16%)]. The pooled prevalence of limited HL in all studies was 22.7% (95% confidence interval 20.6-24.8%), but study heterogeneity limited the generalizability of this combined prevalence. The review identified associations between limited HL and socio-economic factors (lower education attainment, lower income), and certain process and outcome measures (lower likelihood of referral for transplant, higher mortality). CONCLUSIONS Limited HL is common among people with CKD and independently associated with socio-economic factors and health outcomes. It may represent an important determinant of inequality in CKD.

Suboptimal blood pressure control in chronic kidney disease stage 3: baseline data from a cohort study in primary care

BackgroundPoorly controlled hypertension is independently associated with mortality, cardiovascular risk and disease progression in chronic kidney disease (CKD). In the UK, CKD stage 3 is principally managed in primary care, including blood pressure (BP) management. Controlling BP is key to improving outcomes in CKD. This study aimed to investigate associations of BP control in people with CKD stage 3.Methods1,741 patients with CKD 3 recruited from 32 general practices for the Renal Risk in Derby Study underwent medical history, clinical assessment and biochemistry testing. BP control was assessed by three standards: National Institute for Health and Clinical Excellence (NICE), National Kidney Foundation Kidney Disease Outcome Quality Initiative (KDOQI) and Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. Descriptive statistics were used to compare characteristics of people achieving and not achieving BP control. Univariate and multivariate logistic regression was used to identify factors associated with BP control.ResultsThe prevalence of hypertension was 88%. Among people with hypertension, 829/1426 (58.1%) achieved NICE BP targets, 512/1426 (35.9%) KDOQI targets and 859/1426 (60.2%) KDIGO targets. Smaller proportions of people with diabetes and/or albuminuria achieved hypertension targets. 615/1426 (43.1%) were only taking one antihypertensive agent. On multivariable analysis, BP control (NICE and KDIGO) was negatively associated with age (NICE odds ratio (OR) 0.27; 95% confidence interval (95% CI) 0.17-0.43) 70–79 compared to <60), diabetes (OR 0.32; 95% CI 0.25-0.43)), and albuminuria (OR 0.56; 95% CI 0.42-0.74)). For the KDOQI target, there was also association with males (OR 0.76; 95% CI 0.60-0.96)) but not diabetes (target not diabetes specific). Older people were less likely to achieve systolic targets (NICE target OR 0.17 (95% CI 0.09,0.32) p < 0.001) and more likely to achieve diastolic targets (OR 2.35 (95% CI 1.11,4.96) p < 0.001) for people >80 compared to < 60).ConclusionsSuboptimal BP control was common in CKD patients with hypertension in this study, particularly those at highest risk of adverse outcomes due to diabetes and or albuminuria. This study suggests there is scope for improving BP control in people with CKD by using more antihypertensive agents in combination while considering issues of adherence and potential side effects.

Change in prevalence of chronic kidney disease in England over time: comparison of nationally representative cross-sectional surveys from 2003 to 2010

Objectives To determine whether the prevalence of chronic kidney disease (CKD) in England has changed over time. Design Cross-sectional analysis of nationally representative Health Survey for England (HSE) random samples. Setting England 2003 and 2009/2010. Survey participants 13 896 adults aged 16+ participating in HSE, adjusted for sampling and non-response, 2009/2010 surveys combined. Main outcome measure Change in prevalence of estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 (as proxy for stage 3–5 CKD), from 2003 to 2009/2010 based on a single serum creatinine measure using an isotope dilution mass spectrometry traceable enzymatic assay in a single laboratory; eGFR derived using Modified Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKDEPI) eGFR formulae. Analysis Multivariate logistic regression modelling to adjust time changes for sociodemographic and clinical factors (body mass index, hypertension, diabetes, lipids). A correction factor was applied to the 2003 HSE serum creatinine to account for a storage effect. Results National prevalence of low eGFR (<60) decreased within each age and gender group for both formulae except in men aged 65–74. Prevalence of obesity and diabetes increased in this period, while there was a decrease in hypertension. Adjustment for demographic and clinical factors led to a significant decrease in CKD between the surveyed periods. The fully adjusted OR for eGFR <60 mL/min/1.73 m2 was 0.75 (0.61 to 0.92) comparing 2009/2010 with 2003 using the MDRD equation, and was similar using the CKDEPI equation 0.73 (0.57 to 0.93). Conclusions The prevalence of a low eGFR indicative of CKD in England appeared to decrease over this 7-year period, despite the rising prevalence of obesity and diabetes, two key causes of CKD. Hypertension prevalence declined and blood pressure control improved but this did not appear to explain the fall. Periodic assessment of eGFR and albuminuria in future HSEs is needed to evaluate trends in CKD.

Chronic kidney disease, albuminuria and socioeconomic status in the Health Surveys for England 2009 and 2010

BACKGROUND Renal replacement therapy rates are inversely related to socioeconomic status (SES) in developed countries. The relationship between chronic kidney disease (CKD) and SES is less clear. This study examined the relationships between SES and CKD and albuminuria in England. METHODS Data from the Health Survey for England 2009 and 2010 were combined. The prevalence of CKD 3-5 and albuminuria was calculated, and logistic regression used to determine their association with five individual-level measures and one area-level measure of SES. RESULTS The prevalence of CKD 3-5 was 5.2% and albuminuria 8.0%. Age-sex-adjusted CKD 3-5 was associated with lack of qualifications [odds ratio (OR) 2.27 (95% confidence interval 1.40-3.69)], low income [OR 1.50 (1.02-2.21)] and renting tenure [OR 1.36 (1.01-1.84)]. Only tenure remained significant in fully adjusted models suggesting that co-variables were on the causal pathway. Albuminuria remained associated with several SES measures on full adjustment: low income [OR 1.55 (1.14-2.11)], no vehicle [OR 1.38 (1.05-1.81)], renting [OR 1.31 [1.03-1.67)] and most deprived area-level quintile [OR 1.55 (1.07-2.25)]. CONCLUSIONS CKD 3-5 and albuminuria were associated with low SES using several measures. For albuminuria this was not explained by known measured causal factors.

Nasal self-swabbing for estimating the prevalence of Staphylococcus aureus in the community

Staphylococcus aureus remains a significant cause of morbidity and mortality and, therefore, a burden on healthcare systems. Our aim was to estimate the current rate of nasal S. aureus carriage in the general population and to determine the feasibility of nasal self-swabbing as a means of detection. Two thousand people (1200 adults and 800 children) from a single NHS general practice in Southampton, UK, were randomly selected from a general practice age sex register, stratified by age and sex, and invited to undertake nasal self-swabbing in their own home. Overall, 362 (32.5%) swabs from adults and 168 (22%) from children were returned. Responses were greater for adults and those of increased age, female gender and decreasing socio-economic deprivation. The overall estimated practice carriage rate of S. aureus directly standardized for age sex was 28% [95% confidence interval (CI) 26.1-30.2%]. Carriage of meticillin-susceptible S. aureus was 27% (95% CI 26.1-30.2%), whilst that of meticillin-resistant S. aureus was 1.9% (95% CI 0.7-3.1%). Although nasal self-swabbing rates were relatively low, they are comparable to other studies and may allow large population-based carriage studies to be undertaken at relatively low cost. Importantly, this study updates prevalence data for S. aureus carriage in the community.

KDIGO-based acute kidney injury criteria operate differently in hospitals and the community—findings from a large population cohort

Background Early recognition of acute kidney injury (AKI) is important. It frequently develops first in the community. KDIGO-based AKI e-alert criteria may help clinicians recognize AKI in hospitals, but their suitability for application in the community is unknown. Methods In a large renal cohort (n = 50 835) in one UK health authority, we applied the NHS England AKI ‘e-alert’ criteria to identify and follow three AKI groups: hospital-acquired AKI (HA-AKI), community-acquired AKI admitted to hospital within 7 days (CAA-AKI) and community-acquired AKI not admitted within 7 days (CANA-AKI). We assessed how AKI criteria operated in each group, based on prior blood tests (number and time lag). We compared 30-day, 1- and 5-year mortality, 90-day renal recovery and chronic renal replacement therapy (RRT). Results In total, 4550 patients met AKI e-alert criteria, 61.1% (2779/4550) with HA-AKI, 22.9% (1042/4550) with CAA-AKI and 16.0% (729/4550) with CANA-AKI. The median number of days since last blood test differed between groups (1, 52 and 69 days, respectively). Thirty-day mortality was similar for HA-AKI and CAA-AKI, but significantly lower for CANA-AKI (24.2, 20.2 and 2.6%, respectively). Five-year mortality was high in all groups, but followed a similar pattern (67.1, 64.7 and 46.2%). Differences in 5-year mortality among those not admitted could be explained by adjusting for comorbidities and restricting to 30-day survivors (hazard ratio 0.91, 95% confidence interval 0.80–1.04, versus hospital AKI). Those with CANA-AKI (versus CAA-AKI) had greater non-recovery at 90 days (11.8 versus 3.5%, P < 0.001) and chronic RRT at 5 years (3.7 versus 1.2%, P < 0.001). Conclusions KDIGO-based AKI criteria operate differently in hospitals and in the community. Some patients may not require immediate admission but are at substantial risk of a poor long-term outcome.

Exploration of Chronic Kidney Disease Prevalence Estimates Using New Measures of Kidney Function in the Health Survey for England

Background Chronic kidney disease (CKD) diagnosis relies on glomerular filtration rate (eGFR) estimation, traditionally using the creatinine-based Modification of Diet in Renal Disease (MDRD) equation. The Chronic Kidney Disease Epidemiology Collaboration (CKDEPI) equation performs better in estimating eGFR and predicting mortality and CKD progression risk. Cystatin C is an alternative glomerular filtration marker less influenced by muscle mass. CKD risk stratification is improved by combining creatinine eGFR with cystatin C and urinary albumin to creatinine ratio (uACR). We aimed to identify the impact of introducing CKDEPI and cystatin C on the estimated prevalence and risk stratification of CKD in England and to describe prevalence and associations of cystatin C. Methods and Findings Cross sectional study of 5799 people in the nationally representative 2009 and 2010 Health Surveys for England. Primary outcome measures: prevalence of MDRD, CKDEPI and cystatin C-defined eGFR<60ml/min/1.73m2; prevalence of CKD biomarker combinations (creatinine, cystatin C, uACR). Using CKDEPI instead of MDRD reduced the prevalence of eGFR<60ml/min/1.73m2 from 6.0% (95% CI 5.4–6.6%) to 5.2% (4.7–5.8%) equivalent to around 340,000 fewer individuals in England. Those reclassified as not having CKD evidenced a lower risk profile. Prevalence of cystatin C eGFR<60ml/min/1.73m2 was 7.7% and independently associated with age, lack of qualifications, being an ex-smoker, BMI, hypertension, and albuminuria. Measuring cystatin C in the 3.9% people with CKDEPI-defined eGFR<60ml/min/1.73m2 without albuminuria (CKD Category G3a A1) reclassified about a third into a lower risk group with one of three biomarkers and two thirds into a group with two of three. Measuring cystatin C in the 6.7% people with CKDEPI eGFR >60ml/min/1.73m2 with albuminuria (CKD Category G1-2) reclassified almost a tenth into a higher risk group. Limitations Cross sectional study, single eGFR measure, no measured (‘true’) GFR. Conclusions Introducing the CKDEPI equation and targeted cystatin C measurement reduces estimated CKD prevalence and improves risk stratification.

Skin Autofluorescence and All-Cause Mortality in Stage 3 CKD

BACKGROUND AND OBJECTIVES Novel markers may help to improve risk prediction in CKD. One potential candidate is tissue advanced glycation end product accumulation, a marker of cumulative metabolic stress, which can be assessed by a simple noninvasive measurement of skin autofluorescence. Skin autofluorescence correlates with higher risk of cardiovascular events and mortality in people with diabetes or people requiring RRT, but its role in earlier CKD has not been studied. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A prospective cohort of 1741 people with CKD stage 3 was recruited from primary care between August 2008 and March 2010. Participants underwent medical history, clinical assessment, blood and urine sampling for biochemistry, and measurement of skin autofluorescence. Kaplan-Meier plots and multivariate Cox proportional hazards models were used to investigate associations between skin autofluorescence (categorical in quartiles) and all-cause mortality. RESULTS In total, 1707 participants had skin autofluorescence measured; 170 (10%) participants died after a median of 3.6 years of follow-up. The most common cause of death was cardiovascular disease (41%). Higher skin autofluorescence was associated significantly with poorer survival (all-cause mortality, P<0.001) on Kaplan-Meier analysis. Univariate and age/sex-adjusted Cox proportional hazards models showed that the highest quartile of skin autofluorescence was associated with all-cause mortality (hazard ratio, 2.64; 95% confidence interval, 1.71 to 4.08; P<0.001 and hazard ratio, 1.84; 95% confidence interval, 1.18 to 2.86; P=0.003, respectively, compared with the lowest quartile). This association was not maintained after additional adjustment to include cardiovascular disease, diabetes, smoking, body mass index, eGFR, albuminuria, and hemoglobin. CONCLUSIONS Skin autofluorescence was not independently associated with all-cause mortality in this study. Additional research is needed to clarify whether it has a role in risk prediction in CKD.

A Systematic Review of the Prevalence and Associations of Limited Health Literacy in CKD

BACKGROUND AND OBJECTIVES The self-management and decision-making skills required to manage CKD successfully may be diminished in those with low health literacy. A 2012 review identified five papers reporting the prevalence of limited health literacy in CKD, largely from United States dialysis populations. The literature has expanded considerably since. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We used systematic review, pooled prevalence analysis, metaregression, and exploration of heterogeneity in studies of patients with CKD (all stages). RESULTS From 433 studies, 15 new studies met the inclusion criteria and were analyzed together with five studies from the 2012 review. These included 13 cross-sectional surveys, five cohort studies (using baseline data), and two using baseline clinical trial data. Most (19 of 20) were from the United States. In total, 12,324 patients were studied (3529 nondialysis CKD, 5289 dialysis, 2560 transplant, and 946 with unspecified CKD; median =198.5; IQR, 128.5-260 per study). Median prevalence of limited health literacy within studies was 23% (IQR, 16%-33%), and pooled prevalence was 25% (95% confidence interval, 20% to 30%) with significant between-study heterogeneity (I2=97%). Pooled prevalence of limited health literacy was 25% (95% confidence interval, 16% to 33%; I2=97%) among patients with CKD not on dialysis, 27% (95% confidence interval, 19% to 35%; I2=96%) among patients on dialysis, and 14% (95% confidence interval, 7% to 21%; I2=97%) among patients with transplants. A higher proportion of nonwhite participants was associated with increased limited health literacy prevalence (P=0.04), but participant age was not (P=0.40). Within studies, nonwhite ethnicity and low socioeconomic status were consistently and independently associated with limited health literacy. Studies were of low or moderate quality. Within-study participant selection criteria had potential to introduce bias. CONCLUSIONS Limited health literacy is common in CKD, especially among individuals with low socioeconomic status and nonwhite ethnicity. This has implications for the design of self-management and decision-making initiatives to promote equity of care and improve quality. Lower prevalence among patients with transplants may reflect selection of patients with higher health literacy for transplantation either because of less comorbidity in this group or as a direct effect of health literacy on access to transplantation.

Validity of estimated prevalence of decreased kidney function and renal replacement therapy from primary care electronic health records compared with national survey and registry data in the United Kingdom

Background Anonymous primary care records are an important resource for observational studies. However, their external validity is unknown in identifying the prevalence of decreased kidney function and renal replacement therapy (RRT). We thus compared the prevalence of decreased kidney function and RRT in the Clinical Practice Research Datalink (CPRD) with a nationally representative survey and national registry. Methods Among all people ≥25 years of age registered in the CPRD for ≥1 year on 31 March 2014, we identified patients with an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2, according to their most recent serum creatinine in the past 5 years using the Chronic Kidney Disease Epidemiology Collaboration equation and patients with recorded diagnoses of RRT. Denominators were the entire population in each age‐sex band irrespective of creatinine measurement. The prevalence of eGFR <60 mL/min/1.73 m2 was compared with that in the Health Survey for England (HSE) 2009/2010 and the prevalence of RRT was compared with that in the UK Renal Registry (UKRR) 2014. Results We analysed 2 761 755 people in CPRD [mean age 53 (SD 17) years, men 49%], of whom 189 581 (6.86%) had an eGFR <60 mL/min/1.73 m2 and 3293 (0.12%) were on RRT. The prevalence of eGFR <60 mL/min/1.73 m2 in CPRD was similar to that in the HSE and the prevalence of RRT was close to that in the UKRR across all age groups in men and women, although the small number of younger patients with an eGFR <60 mL/min/1.73 m2 in the HSE might have hampered precise comparison. Conclusions UK primary care data have good external validity for the prevalence of decreased kidney function and RRT.