Late referral for assessment of renal failure

Socio-economic status influences chronic kidney disease prevalence in primary care: a community-based cross-sectional analysis

BACKGROUND

Primary care chronic kidney disease (CKD) registers report widely varying prevalence within the UK. We examined the effects of laboratory ascertainment and adjusting for practice-level variables on the variation in CKD prevalence. We carried out an Ayrshire-wide laboratory database analysis of primary care practices (PCPs).

METHODS

We analysed 54 PCPs with 313 639 registered patients aged ≥ 18. All patients with a low estimated glomerular filtration rate (<60 mL/min/1.73 m(2)) had their serum creatinine values extracted from 1st January 2009 to 31st March 2012. Individuals with CKD stage 3-5 were identified with an algorithm that confirmed chronicity. These data were linked to PCP attributes from Information Services Division, Scotland. Using laboratory-ascertained CKD prevalence, we examined whether adjusting for practice-level factors [socio-economic status (SES), rurality and patients to general practitioner ratio (PGR)] and patient-level factors (age, gender) explained some of the observed variation among PCPs. Individual and combined hierarchical multilinear regression models were used.

RESULTS

Eighteen thousand two hundred and eighty-five (5.8%) had CKD stage 3-5 on 31 March 2011. SES, rurality and PGR predicted 39% (F(3,50) = 12.37, P < 0.001) of the variation in prevalence with SES exerting the most influence (25%). With the stepwise addition of explanatory variables, variation between practices fell from 3.9-fold using PCP register prevalence to laboratory ascertained (3.1-fold variation), with age and gender adjustment (further fall to 2.1-fold), and lastly to 1.8-fold variation with adjustment for SES. Funnel plots using these adjustments reduced the number of outliers outside of 3 SD from 15 to 7 to 6, and outliers between 2 and 3 SD by 16 to 13 to 5.

CONCLUSIONS

Laboratory ascertainment is practicable, reduces variation and facilitates benchmarking. PCP attributes other than age and gender impact on prevalence. Over a third of variation in CKD prevalence among PCPs can be explained by rurality, PGR and especially SES even after age and gender stratification.

Lithium usage and renal function testing in a large UK community population; a case-control study

OBJECTIVE

This study investigates the prevalence of lithium use, monitoring practice and associated effects on renal function in a large UK community sample.

METHOD

A large population-based renal function database was cross-referenced with a general practitioner database of 404,673 patients. The renal function of patients prescribed lithium during the 2-year period was compared with that of matched controls. The renal monitoring patterns of these cases were investigated in a naturalistic observational study. Data underwent parametric testing - continuous variables by analysis of variance, with appropriate adjustment, and categorical outcomes by χ(2) testing. Block analysis of variance was undertaken on case-control data.

RESULTS

A total of 422 patients in the database were prescribed lithium. Renal function monitoring in accordance with published guidelines occurred in 69% of patients. Patients taking lithium had a significantly higher serum creatinine (5.8 μmol/L, P<.001) and lower glomerular filtration rate (5.9 ml/min, P<.001) when compared to matched controls.

CONCLUSIONS

This is the first study carried out in a large community sample. Lithium remains widely prescribed in the community setting. The study confirms that lithium has a statistically and clinically significant negative effect on renal function. Despite published guidelines and recognition of the importance of serial measurements, monitoring of renal function is inconsistent.

Identifying additional patients with diabetic nephropathy using the UK primary care initiative

AIMS

The aim of this study was to use general practice data to estimate the prevalence of diabetic nephropathy within the registered diabetes patients and examine variation in practice prevalence and management performance since introduction of this initiative.

METHODS

Reported quality indicators from the Northern Ireland General Practice Quality and Outcomes Framework were analysed for diabetes and diabetic nephropathy prevalence and management in the period 2004-2008. Variation in prevalence at practice level was assessed using multiple linear regression adjusting for age, practice size, deprivation and glycaemic control.

RESULTS

In 2006-2007, 57,454 (4.1%) adult diabetic patients were registered in the denominator population of 1.4 million compared with 51,923 (3.8%) in 2004-2005 (mean practice range 0.5-7.7%). Diabetic nephropathy prevalence was 15.1 and 11.5%, respectively (8688 and 5955 patients). Documented diabetic nephropathy prevalence showed marked variation across practices (range 0-100%) and was significantly negatively correlated with diabetes list size, albumin creatinine ratio testing rates and renin-angiotensin-aldosterone system blockade use and positively correlated with exception reporting rates. Specifically, for every increase in 100 diabetic patients to a register, documented diabetic nephropathy prevalence reduced by 40% (P=0.003). On the positive side, median albumin-creatinine ratio testing rates doubled to 82% compared with figures in the pre-Framework era.

CONCLUSIONS

Implementation of the Northern Ireland General Practice Quality and Outcomes Framework has positively benefitted testing for diabetic nephropathy and increased numbers of detected patients in a short space of time. Large variation in diabetic nephropathy prevalence remains and is associated with diabetes registry size, screening and treatment practices, suggesting that understanding this variation may help detect and better manage diabetic nephropathy.

The finding of reduced estimated glomerular filtration rate is associated with increased mortality in a large UK population

BACKGROUND

CKD as defined by KDIGO/KDOQI has been shown to affect ~ 8.5% of the UK population. The prevalence of CKD in the UK is similar to that in the USA, yet incident dialysis rates are dramatically different. This retrospective cohort study investigates the association between reduced kidney function and mortality in a large UK population.

METHODS

All serum creatinine results covering Northern Ireland's 1.7 million population were collected between 1 January 2001 and 31 December 2002. Estimated glomerular filtration rates (eGFR) were calculated for all serum creatinine measurements using four-variable MDRD equation (IDMS aligned). Patients were followed up for both all-cause and cardiovascular mortality data until the end of December 2006. Patients on renal replacement therapy were excluded. Subgroup analysis in the 75,345 subjects enrolled within a parallel primary care study permitted additional survival analysis with adjustment for traditional cardiovascular risk factors.

RESULTS

A total of 1,967,827 serum creatinine results from 533,798 patients were collected. During the period of follow-up, 59,980 deaths occurred. In multivariate survival analysis, using eGFR as a time-varying covariate, a graded association between CKD (defined by eGFR) and all-cause mortality was identified. Compared with participants with an eGFR of > 60 mL/min/1.73 m(2), the adjusted hazard ratios (and 95% confidence intervals) for participants with an eGFR of 45-59 mL/min/1.73 m(2) was 1.02 (0.99-1.04), an eGFR of 30-44 mL/min/1.73 m(2) was 1.44 (1.40-1.47), an eGFR of 15-29 mL/min/1.73 m(2) was 2.12 (2.05-2.20) and an eGFR of < 15 mL/min/1.73 m(2) was 3.46 (3.24-3.70). Significantly, increased all-cause mortality was associated with an eGFR < 45 mL/min/1.73 m(2) following adjustment for age and gender. The association between cardiovascular mortality and reduced renal function continued to be significant for participants with an eGFR of 45-65 mL/min/1.73 m(2). Subgroup analysis in 75,345 individuals with more detailed clinical information available confirmed this association following adjustment for traditional cardiovascular risk factors in addition to age and gender.

CONCLUSIONS

This study demonstrates a graded association between reduced renal function as represented by eGFR and mortality in a UK population. The all-cause and cardiovascular mortality risk increases sharply when estimated GFR falls < 45 mL/min/1.73 m(2). The association between an eGFR measured between 45 and 65 mL/min/1.73 m(2) and cardiovascular mortality persists in this cohort and highlights the ongoing uncertainty in accurately categorizing renal dysfunction.

Screening for chronic kidney disease: where does Europe go?

This review discusses various screening approaches for chronic kidney disease that are used in Europe. The criterion for defining chronic kidney disease in the various programs differs but is frequently limited to estimated glomerular filtration rate, thus offering only data on chronic kidney disease stages 3 and higher; however, screening should not be limited to measuring only estimated glomerular filtration rate but should also include a measure of microalbuminuria, because this will offer identification of chronic kidney disease stages 1 and 2. Defining these earlier stages is of importance because the risk for developing end-stage renal disease that is associated with stages 1 and 2 is nearly equal to the risk that is associated with stage 3. Moreover, the risk for cardiovascular events in stages 1 and 2 is equal to that in stage 3. Various reports argue that costs of screening programs in general practitioner or outpatient offices are high and that they are cost-effective only for preventing end-stage renal disease when they are limited to target groups, such as patients with diabetes or hypertension and elderly. The benefits of screening programs, however, should not be evaluated only with respect to the prevention of renal events but should also include the benefits of preventing cardiovascular events. The use of preselection based on either an impaired estimated glomerular filtration rate or on protein-dipstick positivity or elevated albuminuria in a morning urine void has been found effective in various European countries as an alternative for targeted screening.

Relationship between Glomerular Filtration Rate and the Prevalence of Metabolic Abnormalities: Results from the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND AND AIMS

National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines recommend that all people with a glomerular filtration rate (GFR) <60 ml/min/1.73 m(2) undergo evaluation for anaemia and metabolic bone disease. We aim to report the prevalence of metabolic complications in adults with low GFR.

METHODS

Analysis of 15,802 non-institutionalised adult participants in the Third National Health and Nutrition Survey (NHANES III), a cross-sectional population-based survey conducted in the United States between 1986 and 1994. Renal function was estimated according the modification of diet in renal disease equation 7 (MDRD GFR), the Cockcroft-Gault formula and by the serum creatinine cut-off points described by Couchoud and colleagues. Haemoglobin <110 g/l occurred in 42.2% [95% confidence interval (CI) 28.3-56.0] of patients with MDRD GFR <30 ml/min/1.73 m(2) [stage 3 chronic kidney disease (CKD)] and 3.5% (95% CI 2.4-4.7) of patients with MDRD GFR between 30 and 60 ml/min/1.73 m(2) (stage 4-5 CKD). Corresponding prevalences for calcium <2.15 mmol/l were 8.2 (95% CI 1.6-14.8) and 3.4 (95% CI 1.7-5.2); for phosphate >1.6 mmol/l, 15.1 (95% CI 5.0-25.3) and 0.3 (95% CI 0-0.6); and for bicarbonate <23 mmol/l, 32.7 (95% CI 19.6-45.9) and 5.7 (95% CI 3.3-8.2), respectively. Similar results were obtained when patients were categorised by the Cockcroft-Gault formula or Couchoud's cut-off points.

CONCLUSIONS

The prevalence of complications in stage 3 CKD is low. These data do not support the recommendation for routine screening for metabolic complications of renal insufficiency in adults seen in primary care settings whose GFR exceeds 30 ml/min/1.73 m(2).