A Comparison of Sodium-Glucose Co-Transporter 2 Inhibitor Kidney Outcome Trial Participants with a Real-World Chronic Kidney Disease Primary Care Population

BACKGROUND/HYPOTHESIS

Observational studies suggest sodium-glucose co-transporter-2 (SGLT2) inhibitor kidney outcome trials are not representative of the broader population of people with chronic kidney disease (CKD). However, there are limited data on the generalisability to those without co-existing type 2 diabetes (T2D), and the representativeness of the EMPA-KIDNEY trial has not been adequately explored. We hypothesised that SGLT2 inhibitor kidney outcome trials are more representative of people with co-existing T2D than those without, and that EMPA-KIDNEY is more representative than previous trials.

METHODS

A cross-sectional analysis of adults with CKD in English primary care was conducted using the Oxford-Royal College of General Practitioners Clinical Information Digital Hub. The proportions that met the eligibility criteria of SGLT2 inhibitor kidney outcome trials were determined, and their characteristics described. Logistic regression analyses were performed to identify factors associated with trial eligibility.

RESULTS

Of 6,670,829 adults, 516,491 (7.7%) with CKD were identified. In the real-world CKD population, 0.9%, 2.2%, and 8.0% met the CREDENCE, DAPA-CKD, and EMPA-KIDNEY eligibility criteria, respectively. All trials were more representative of people with co-existing T2D than those without T2D. Trial participants were 9-14 years younger than the real-world CKD population, and had more advanced CKD, including higher levels of albuminuria. A higher proportion of the CREDENCE (100%), DAPA-CKD (67.6%) and EMPA-KIDNEY (44.5%) trial participants had T2D compared to the real-world CKD population (32.8%). Renin-angiotensin system inhibitors were prescribed in almost all trial participants, compared to less than half of the real-world CKD population. Females were under-represented and less likely to be eligible for the trials.

CONCLUSION

SGLT2 inhibitor kidney outcome trials represent a sub-group of people with CKD at high risk of adverse kidney events. Out study highlights the importance of complementing trials with real-world studies, exploring the effectiveness of SGLT2 inhibitors in the broader population of people with CKD.

Implementation of chronic kidney disease guidelines for sodium-glucose co-transporter-2 inhibitor use in primary care in the UK: a cross-sectional study

Background

The cardiovascular and kidney benefits of sodium-glucose co-transporter-2 (SGLT2) inhibitors in people with chronic kidney disease (CKD) are well established. The implementation of updated SGLT2 inhibitor guidelines and prescribing in the real-world CKD population remains largely unknown.

Methods

A cross-sectional study of adults with CKD registered with UK primary care practices in the Oxford-Royal College of General Practitioners Research and Surveillance Centre network on the 31st December 2022 was undertaken. Pseudonymised data from electronic health records held securely within the Oxford-Royal College of General Practitioners Clinical Informatics Digital Hub (ORCHID) were extracted. An update to a previously described ontological approach was used to identify the study population, using a combination of Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) indicating a diagnosis of CKD and laboratory confirmed CKD based on Kidney Disease: Improving Global Outcomes (KDIGO) diagnostic criteria. We examined the extent to which SGLT2 inhibitor guidelines apply to and are then implemented in adults with CKD. A logistic regression model was used to identify factors associated with SGLT2 inhibitor prescribing, reported as odds ratios (ORs) with 95% confidence intervals (CI). The four guidelines under investigation were the United Kingdom Kidney Association (UKKA) Clinical Practice Guideline SGLT2 Inhibition in Adults with Kidney Disease (October 2021), American Diabetes Association (ADA) and KDIGO Consensus Report on Diabetes Management in CKD (October 2022), National Institute for Health and Care Excellence (NICE) Guideline Type 2 Diabetes in Adults: Management (June 2022), and NICE Technology Appraisal Dapagliflozin for Treating CKD (March 2022).

Findings

Of 6,670,829 adults, we identified 516,491 (7.7%) with CKD, including 32.8% (n = 169,443) who had co-existing type 2 diabetes (T2D). 26.8% (n = 138,183) of the overall CKD population had a guideline directed indication for SGLT2 inhibitor treatment. A higher proportion of people with CKD and co-existing T2D were indicated for treatment, compared to those without T2D (62.8% [n = 106,468] vs. 9.1% [n = 31,715]). SGLT2 inhibitors were prescribed to 17.0% (n = 23,466) of those with an indication for treatment, and prescriptions were predominantly in those with co-existing T2D; 22.0% (n = 23,464) in those with T2D, and <0.1% (n = 2) in those without T2D. In adjusted multivariable analysis of people with CKD and T2D, females (OR 0.69, 95% CI 0.67-0.72, p <0.0001), individuals of Black ethnicity (OR 0.84, 95% CI 0.77-0.91, p <0.0001) and those of lower socio-economic status (OR 0.72, 95% CI 0.68-0.76, p <0.0001) were less likely to be prescribed an SGLT2 inhibitor. Those with an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 had a lower likelihood of receiving an SGLT2 inhibitor, compared to those with an eGFR ≥60 mL/min/1.73 m2 (eGFR 45-60 mL/min/1.73 m2 OR 0.65, 95% CI 0.62-0.68, p <0.0001, eGFR 30-45 mL/min/1.73 m2 OR 0.73, 95% CI 0.69-0.78, p <0.0001, eGFR 15-30 mL/min/1.73 m2 OR 0.52, 95% CI 0.46-0.60, p <0.0001, eGFR <15 mL/min/1.73 m2 OR 0.03, 95% CI 0.00-0.23, p = 0.0037, respectively). Those with albuminuria (urine albumin-to-creatinine ratio 3-30 mg/mmol) were less likely to be prescribed an SGLT2 inhibitor, compared to those without albuminuria (OR 0.78, 95% CI 0.75-0.82, p <0.0001).

Interpretation

SGLT2 inhibitor guidelines in CKD have not yet been successfully implemented into clinical practice, most notably in those without co-existing T2D. Individuals at higher risk of adverse outcomes are paradoxically less likely to receive SGLT2 inhibitor treatment. The timeframe between the publication of guidelines and data extraction may have been too short to observe changes in clinical practice. Enhanced efforts to embed SGLT2 inhibitors equitably into routine care for people with CKD are urgently needed, particularly in those at highest risk of adverse outcomes and in the absence of T2D.

Funding

None.

Sodium-glucose cotransporter-2 inhibitors and kidney outcomes in real-world type 2 diabetes populations: A systematic review and meta-analysis of observational studies

AIM

To conduct a systematic review of observational studies to explore the real-world kidney benefits of sodium-glucose cotransporter-2 (SGLT2) inhibitors in a large and diverse population of adults with type 2 diabetes (T2D).

MATERIALS AND METHODS

We searched MEDLINE, EMBASE and Web of Science for observational studies that investigated kidney disease progression in adults with T2D treated with SGLT2 inhibitors compared to other glucose-lowering therapies. Studies published from database inception to July 2022 were independently reviewed by two authors and evaluated using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool. A random-effects meta-analysis was performed on studies with comparable outcome data, reported as hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS

We identified 34 studies performed across 15 countries with a total population of 1 494 373 for inclusion. In the meta-analysis of 20 studies, SGLT2 inhibitors were associated with a 46% lower risk of kidney failure events compared with other glucose-lowering drugs (HR 0.54, 95% CI 0.47-0.63). This finding was consistent across multiple sensitivity analyses and was independent of baseline estimated glomerular filtration rate (eGFR) or albuminuria status. SGLT2 inhibitors were associated with a lower risk of kidney failure when compared with dipeptidyl peptidase-4 inhibitors and a combination of other glucose-lowering drug classes (HR 0.50, 95% CI 0.38-0.67 and HR 0.51, 95% CI 0.44-0.59, respectively). However, when compared to glucagon-like peptide 1 receptor agonists there was no statistically significant difference in the risk of kidney failure (HR 0.93, 95% CI 0.80-1.09).

CONCLUSIONS

The reno-protective benefits of SGLT2 inhibitors apply to a broad population of adults with T2D treated in routine clinical practice, including those at lower risk of kidney events with normal eGFR and without albuminuria. These findings support the early use of SGLT2 inhibitors in T2D for preservation of kidney health.

Serum sodium concentration and the progression of established chronic kidney disease

Background

Higher serum sodium concentration has been reported to be a risk factor for the development of incident chronic kidney disease (CKD), but its relationship with the progression of established CKD has not been investigated. We hypothesised that increased serum sodium concentration is a risk factor for estimated glomerular filtration rate (eGFR) decline in CKD.

Methods

This was a retrospective cohort study using data collected over a 6-year period, with baseline data obtained during the first 2 years. We included patients known to our renal service who had had a minimum of three blood tests every 2 years and an eGFR of < 60 mL/min/1.73 m² at baseline. Exclusion criteria were renal replacement therapy, diabetes mellitus, heart failure and decompensated liver disease. A multiple linear regression model investigated the relationship between baseline serum sodium and eGFR decline after adjustment for confounding factors.

Results

7418 blood results from 326 patients were included. There was no relationship between serum sodium concentration and estimated glomerular filtration rate at baseline. After multivariable adjustment, a 1 mmol/L increase in baseline serum sodium was associated with a 1.5 mL/min/1.73 m² decline in eGFR during the study period (95% CI 0.9, 2.0). A reduction in eGFR was not associated with significant changes in serum sodium concentration over 6 years.

Conclusion

Higher serum sodium concentration is associated with the progression of CKD, independently of other established risk factors. Conversely, significant alterations in serum sodium concentration do not occur with declining kidney function.

An ontological approach to identifying cases of chronic kidney disease from routine primary care data: a cross-sectional study

Background

Accurately identifying cases of chronic kidney disease (CKD) from primary care data facilitates the management of patients, and is vital for surveillance and research purposes. Ontologies provide a systematic and transparent basis for clinical case definition and can be used to identify clinical codes relevant to all aspects of CKD care and its diagnosis.

Methods

We used routinely collected primary care data from the Royal College of General Practitioners Research and Surveillance Centre. A domain ontology was created and presented in Ontology Web Language (OWL). The identification and staging of CKD was then carried out using two parallel approaches: (1) clinical coding consistent with a diagnosis of CKD; (2) laboratory-confirmed CKD, based on estimated glomerular filtration rate (eGFR) or the presence of proteinuria.

Results

The study cohort comprised of 1.2 million individuals aged 18 years and over. 78,153 (6.4%) of the population had CKD on the basis of an eGFR of < 60 mL/min/1.73m², and a further 7366 (0.6%) individuals were identified as having CKD due to proteinuria. 19,504 (1.6%) individuals without laboratory-confirmed CKD had a clinical code consistent with the diagnosis. In addition, a subset of codes allowed for 1348 (0.1%) individuals receiving renal replacement therapy to be identified.

Conclusions

Finding cases of CKD from primary care data using an ontological approach may have greater sensitivity than less comprehensive methods, particularly for identifying those receiving renal replacement therapy or with CKD stages 1 or 2. However, the possibility of inaccurate coding may limit the specificity of this method.

Diabetic nephropathy: where are we on the journey from pathophysiology to treatment?

Diabetic nephropathy affects 30-40% of people with diabetes, and is the leading cause of end-stage kidney disease. The current treatment paradigm relies on early detection, glycaemic control and tight blood pressure management with preferential use of renin-angiotensin system blockade. This strategy has transformed outcomes in diabetic kidney disease over the last 20 years. Over the last two decades we have also witnessed significant advances in the understanding of the pathophysiology of diabetic nephropathy; however, despite this new knowledge, we have yet to develop new treatments of proven efficacy. Whilst a continued emphasis on preclinical and clinical research is clearly needed, clinicians treating people with diabetes should not forget that, in the short term, the greatest gains are likely to be realised by more consistent deployment of existing therapies.

The health impacts of dietary sodium and a low-salt diet

High salt intake is now endemic worldwide. It contributes to the generation and maintenance of high blood pressure, which is now the biggest risk factor for global disease. There is now compelling evidence to support salt reduction in hypertensives and a substantial body of evidence to support salt reduction in the general population to reduce risk of death from cardiovascular disease. In specific diseases such as heart failure and chronic kidney disease, guidelines support the World Health Organization target for reduced salt intake at 5 g daily. Achieving a diet that is lower in salt has challenges, but is more likely to be achieved through salt reduction strategies particularly focused on processed food and through educational programs. To be effective, these interventions require collaboration between industry, health agencies and governments.

Altering plasma sodium concentration rapidly changes blood pressure during haemodialysis

BACKGROUND

Plasma sodium is increased following each meal containing salt. There is an increasing interest in the effects of plasma sodium concentration, and it has been suggested that it may have direct effects on blood pressure (BP) and possibly influences endothelial function. Experimental increases of plasma sodium concentration rapidly raise BP even when extracellular volume falls.

METHODS

Ten patients with end-stage renal failure established on haemodialysis were studied during the first 2 h of dialysis without fluid removal during this period. They were randomized to receive haemodialysis with (i) dialysate sodium concentration prescribed to 135 mmol/L and (ii) 145 mmol/L in random order in a prospective, single-blinded crossover study. BP measurements and blood samples were taken every 30 min.

RESULTS

Pre-dialysis sitting BP was 137/76 ± 7/3 mmHg. Lower dialysate sodium concentration (135 mmol/L) reduced plasma sodium concentration [139.49 ± 0.67 to 135.94 ± 0.52 mmol/L (P < 0.001)], whereas plasma sodium concentration was not altered by higher dialysate sodium (145 mmol/L) (140.17 ± 0.66 mmol/L at baseline to 140.72 ± 0.43 mmol/L at 120 min). Systolic BP was lower with dialysate sodium concentration 135 mmol/L [area under the curve (AUC) 15823.50 ± 777.15 (mmHg)min] compared with 145 mmol/L [AUC 17018.20 ± 1102.17 (mmHg)min], mean difference 1194.70 ± 488.41 (mmHg)min, P < 0.05. There was a significant positive relationship between change in plasma sodium concentration and change in systolic BP. This direct relationship suggests that a fall of 1 mmol/L in plasma sodium concentration would be associated with a 1.7 mmHg reduction in systolic BP (P < 0.05).

CONCLUSIONS

The potential mechanism for the increase in BP seen with salt intake may be through small but significant changes in plasma sodium concentration.

Altered dietary salt intake for preventing and treating diabetic kidney disease

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor for increased blood pressure (BP) and a modest reduction in salt intake lowers BP whether BP levels are normal or raised. Tight control of BP in diabetics lowers the risk of strokes, heart attacks and heart failure and slows the progression of diabetic kidney disease (DKD). Currently there is no consensus in restricting salt intake in diabetic patients.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and DKD.

SEARCH STRATEGY

In January 2010, we searched the Cochrane Renal Group's Specialised Register, CENTRAL (in The Cochrane Library), MEDLINE (from 1966) and EMBASE (from 1980) to identify appropriate articles.

SELECTION CRITERIA

We included all randomised controlled trials of salt reduction in individuals with type 1 and type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion with a third independent author. We calculated mean effect sizes using both the fixed-effect and random-effects models.

MAIN RESULTS

Thirteen studies (254 individuals) met our inclusion criteria. These included 75 individuals with type 1 diabetes and 158 individuals with type 2 diabetes. The median reduction in urinary sodium was 203 mmol/24 h (11.9 g/day) in type 1 diabetes and 125 mmol/24 h (7.3 g/day) in type 2 diabetes. The median duration of salt restriction was one week in both type 1 and type 2 diabetes. BP was reduced in both type 1 and type 2 diabetes. In type 1 diabetes (56 individuals), salt restriction reduced BP by -7.11/-3.13 mm Hg (systolic/diastolic); 95% CI: systolic BP (SBP) -9.13 to -5.10; diastolic BP (DBP) -4.28 to -1.98). In type 2 diabetes (56 individuals), salt restriction reduced BP by -6.90/-2.87 mm Hg (95% CI: SBP -9.84 to -3.95; DBP -4.39 to -1.35). There was a greater reduction in BP in normotensive patients, possibly due to a larger decrease in salt intake in this group.

AUTHORS' CONCLUSIONS

Although the studies are not extensive, this meta-analysis shows a large fall in BP with salt restriction, similar to that of single drug therapy. All diabetics should consider reducing salt intake at least to less than 5-6 g/day in keeping with current recommendations for the general population and may consider lowering salt intake to lower levels, although further studies are needed.

Transcutaneous bilirubinometry as a screening tool for neonatal jaundice

Between 25 and 50% of all term newborns develop clinical jaundice, and a serum bilirubin level above 260 microml/l (15 mg/dl) is found in 3% of normal term infants. In the United Kingdom many newborn infants with clinical jaundice have blood samples sent to biochemistry laboratories for assessment of the plasma bilirubin concentration. We planned to assess the cost in terms of finance, medical staff time, numbers of blood samples, and family delay in leaving hospital. We demonstrated that reflectance bilirubinometry is a reliable screening method for identifying which caucasian infants require to have plasma bilirubin concentrations measured in the laboratory. The Minolta Airshields transcutaneous bilirubinometer provided reproducible data, saved time and costs, and often spared infants a capillary or venous blood sample. The transcutaneous bilirubinometer provides a digital assessment of skin pigmentation by xenon reflectance. It has previously been shown to be possible to derive an estimate of plasma bilirubin from the number displayed by the meter and it is suggested as a method for identifying which infants need plasma bilirubin estimations.