Evaluation of GFR Estimating Equations in the General Community: Implications for Screening

Prevalence and Risk Factors of Chronic Kidney Disease in the General Population in Abidjan, Côte d'Ivoire: A Cross-sectional Study

Chronic kidney disease (CKD) is a major cause of morbidity and mortality worldwide, but few studies are available on CKD in Cote d'Ivoire. We aimed to assess the prevalence of CKD and identify its associated factors in the general population in Abidjan in 2016 in a cross-sectional study that included 1418 subjects. We did not receive laboratory data for 38 subjects, including serum creatinine data. Of the 1380 remaining subjects, 138 cases of CKD were included in the study (10% prevalence). We observed a female predominance (sex ratio = 0.81), and the mean age was 43.7 ± 14.5 years. Histories of hypertension (HTN) (29.7%) and diabetes (10.1%) were reported. The main clinical signs were high blood pressure (51.4%), obesity (21%), proteinuria (37.9%), and hematuria (37.4%). The glomerular filtration rate (GFR) was <60 mL/min in 8.2% of cases according to the Modification of Diet in Renal Disease equation, in 8.6% according to the CKD Epidemiology Collaboration equation, and in 12.6% according to the Cockroft-Gault (CG) equation. The other laboratory signs were hyperglycemia (51.4%), hypercholesterolemia (34.1%), and hyperlipidemia (21%). In the multivariate analysis, factors such as female sex (P = 0.013), age >55 years (P = 0.02), a history of HTN (P = 0.001), hypercholesterolemia (P = 0.010), and hyperlipidemia (P = 0.009) were associated with the risk of CKD. The prevalence of CKD was high in our study. The CG equation should not be used to estimate the GFR in the general population. Prevention involves managing modifiable risk factors.

Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation

A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.

[Epidemiology of chronic kidney disease in the Democratic Republic of Congo: review of cross-sectional studies from Kinshasa, the capital]

Chronic kidney disease (CKD) is a worldwide public health problem. Little is known about its burden in Africa. This paper reviews the knowledge of CKD in Kinshasa, summarizing four studies undertaken in the general population and traditional health system of Kinshasa. CKD was defined by either kidney damage (proteinuria> or =300 mg/day) or reduced kidney function (eGFR<60 ml/min/1.73 m(2)). In the general population, the prevalence of CKD all stage is 12.4 %. Our work shows also the high prevalence of proteinuria among subjects who do not have diabetes or hypertension, the lack of early detection and management of CKD risk factors in the traditional health care system leading to late referral or premature deaths, and the limits of renal replacement treatment. CKD affects young people in the DRC, in contrast to the United States, where CKD is more prevalent in older people. Major determinants of CKD in our studies were hypertension, diabetes, overweight, age, lower socioeconomic status, and Human immunodeficiency virus (HIV) infection. Glomerular nephropathy (mainly focal segmental glomerulosclerosis) remains the leading cause of end stage renal disease. An annual screening of the population for proteinuria and CKD risk factors is feasible and will, it is hoped, provide the basis for building a nationwide prevention strategy.

A comparison of three methods to estimate baseline creatinine for RIFLE classification

BACKGROUND

A pre-morbid 'baseline' creatinine is required in order to diagnose and stage acute kidney injury (AKI) using the RIFLE classification. Estimation of baseline creatinine by solving the Modification of Diet in Renal Disease (MDRD) equation assuming a glomerular filtration rate of 75 ml/min/1.73 m(2) has been widely used but never validated.

METHODS

We analysed four cohorts of intensive care unit (ICU) patients from three centres (two from Pittsburgh and one from Mayo and Austin). Three cohorts consisted of preselected patients without AKI (Pittsburgh 1 n = 1048, Mayo n = 737, Austin n = 333), and measured creatinine values in these cohorts were taken to represent baseline creatinine values. The last cohort (Pittsburgh 2 n = 468) consisted of unselected ICU patients with baseline creatinine values recorded within 1 year before ICU admission. Using the Pittsburgh 1 cohort, we derived an equation using the same anthropometric variables as the MDRD equation: baseline creatinine = 0.74 - 0.2 (if female) + 0.08 (if black) + 0.003 × age (in years). We then compared measured creatinine in the Mayo and Austin cohorts and recorded creatinine in the Pittsburgh 2 cohort to the estimated creatinine from: (i) the MDRD equation; (ii) our new equation; (iii) a gender-fixed creatinine of 0.8 mg/dl for females and 1.0 mg/dl for males.

RESULTS

Using any of the three methods, the median absolute error of the estimates was of the order of 0.1-0.2 mg/dl, and overall accuracy was similar. When the definition of AKI was limited to the severity grades of Injury and Failure, all three methods were able to generate 78-90% reliable results for preselected normal range cohorts, and 63-70% for the unselected cohort of ICU patients.

CONCLUSIONS

Estimates of incidence of AKI in the critically ill using RIFLE classification can be affected by the bias and limited accuracy of methods to estimate baseline creatinine. Whenever possible, recorded creatinine values should be used as a reference of baseline. The use of the MDRD equation to estimate baseline creatinine when it is unknown may over- or underestimate some mild (Risk) AKI cases but is unlikely to misclassify patients in Injury and Failure.

When laboratories report estimated glomerular filtration rates in addition to serum creatinines, nephrology consults increase

Serum creatinine alone can be difficult to interpret as a measure of kidney function such that chronic kidney disease might be under-recognized in the general population. In the province of Ontario, Canada, all outpatient laboratories now report estimated glomerular filtration rate (eGFR) in addition to serum creatinine. To determine the impact of this reporting on clinical practice, we linked health administrative data for more than 8 million adults of age 25 years or older over an almost 10-year period and conducted a population-based intervention analysis with seasonal time-series modeling to determine overall trends in the number and type of patients seen by nephrologists. Compared to the period when only serum creatinines were reported, the number of patients seen in consultation by nephrologists increased after eGFR reporting by an average of 24% (an absolute increase of 2.9 consults per 100,000 adults), an increase of about 23 consults per nephrologist per year. The greatest increases were seen in women (39% increase) and those 80 years of age and older (58% increase). Our study found that eGFR reporting was associated with a sudden increase in the number of nephrology consults. However, it remains to be seen whether the routine reporting of eGFR results in improved treatment and outcomes for those with chronic kidney disease.

Excessive fluid intake as a novel cause of proteinuria

As part of a community screening study to assess the long-term health outcomes among residents of Walkerton, Ontario, after contamination of its municipal water supply by Escherichia coli O157:H7 and Campylobacter in 2000, we identified 100 adults who had proteinuria and polyuria but no medical history or medication use to explain their condition. Fifty-six of the 100 participants underwent both initial and confirmatory urine concentration tests, which showed that their urine osmolality could reach normal levels. We then instructed them to reduce their fluid intake to less than 2 L/d for 1 week. The proteinuria and polyuria were largely reversed by this manoeuvre. We do not know at this time whether the proteinuria associated with excessive fluid intake in these otherwise healthy people will affect their kidney function in the long term.

Understanding estimated glomerular filtration rate: implications for identifying chronic kidney disease

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) can be estimated using serum markers such as serum creatinine (SCr) or cystatin C. This review presents new insights into estimated GFR based on theory, validation studies, SCr assay standardization, cystatin C, and longitudinal comparison with measured GFR.

RECENT FINDINGS

The estimation of GFR by SCr differs in health and in chronic kidney disease (CKD) due to differences in GFR range and in creatinine production between these two populations. Among populations with normal baseline GFR, there is a more rapid decline in measured GFR than in SCr-based estimated GFR. While elevated SCr is specific for CKD, other disease processes may lead to elevated cystatin C. Validation is improved by refitting equation coefficients to compare populations, recognizing the asymmetry between estimated GFR and measured GFR, and using residual plots instead of Bland-Altman plots to assess bias.

SUMMARY

As a screening test, SCr should be interpreted as a marker of CKD probability in the context of the patient's clinical presentation. Measured GFR or creatinine clearance may be helpful in high-risk patients with normal SCr levels. GFR estimating equations should be reserved for patients with identified CKD. Standardized SCr and cystatin C assays are needed.