Comparison of Various Equations for Estimating GFR in Malawi: How to Determine Renal Function in Resource Limited Settings?

Prospective cohort study to identify prevalence, risk factors and outcomes of infection associated kidney disease in a regional hospital in Malawi

OBJECTIVES

Acute kidney injury (AKI) is a common and severe complication of community acquired infection, but data on impact in sub-Saharan Africa (SSA) are lacking. We determined prevalence, risk factors and outcomes of infection associated kidney disease in adults in Malawi.

DESIGN

A prospective cohort study of adults admitted to hospital with infection, from February 2021 to June 2021, collecting demographic, clinical, laboratory and ultrasonography data.

SETTING

Adults admitted to a regional hospital in Southern Region, Malawi.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcomes were prevalence of kidney disease and mortality by Cox proportional hazard model. AKI was defined according to Kidney Disease Improving Global Outcomes (KDIGO) guidelines. Secondary outcomes were risk factors for AKI identified by logistic regression and prevalence of chronic kidney disease at 3 months.

RESULTS

We recruited 101 patients presenting to hospital with infection. Median age was 38 years (IQR: 29-48 years), 88 had known HIV status of which 53 (60%) were living with HIV, and of these 42 (79%) were receiving antiretroviral therapy. AKI was present in 33/101 at baseline, of which 18/33 (55%) cases were severe (KDIGO stage 3). At 3 months, 28/94 (30%) participants had died, while 7/61 (11%) of survivors had chronic kidney disease. AKI was associated with older age (age: 60 years vs 40 years, OR: 3.88, 95% CI 1.82 to 16.64), and HIV positivity (OR: 4.08, 95% CI 1.28 to 15.67). Living with HIV was independently associated with death (HR: 3.97, 95% CI 1.07 to 14.69).

CONCLUSIONS

Kidney disease is common among hospitalised adults with infection in Malawi, with significant kidney impairment identified at 3 months. Our study highlights the difficulty in diagnosing acute and chronic kidney disease, and the need for more accurate methods than creatinine based estimated glomerular filtration rate (eGFR) equations for populations in Africa. Patients with kidney impairment identified in hospital should be prioritised for follow-up.

Kidney disease burden in an Asian Indian population: Effect of the new 2021 serum creatinine CKD-EPI equation

AIMS

CKD-EPI (chronic kidney disease-epidemiological) serum creatinine equation is widely accepted for calculating estimated glomerular filtration rate (eGFR). The effect of transitioning from the older 2009 to the newer race-independent 2021 CKD-EPI equation on the estimated kidney disease burden (eKDB) was studied in an Asian-Indian population.

METHODS

The study included 1156 adults, the two equations were compared for agreement (Bland-Altman and Cohen's kappa) and concordance (Lin's correlation and test for proportions).

RESULTS

The 2021 CKD-EPI increased the eGFR (positive-bias), independent of age-group, gender or presence of type 2 diabetes mellitus (T2DM) and hypertension (HTN). Thus, the eKDB was significantly decreased by 2021 CKD-EPI equation. The agreement was highest for the age-group 31-40 years (95.8 % versus 87.5 % for > 50 years). Besides, the eGFR category was shifted from G3 to G1 in 8.2 % (95 % CI: 6.8-9.9) individuals by 2021 CKD-EPI. The effect of transition on eKDB was greater in individuals > 50 years (7.4 %) or with HTN (6.3 %).

CONCLUSION

In comparison to the old equation, the 2021 CKD-EPI equation increased the eGFR, lowering the eKDB in this Asian-Indian cohort. The degree of lowering was affected by age-group, and presence of T2DM /HTN, but independent of gender.

Using race in the estimation of glomerular filtration rates: time for a reversal?

PURPOSE OF REVIEW

Bedside estimates of renal function are essential for clinical practice in the modern era and have largely relied on serum creatinine concentrations despite the known drawbacks associated with this choice of biomarker, including the fact that creatinine clearance overestimates the glomerular filtration rate.

RECENT FINDINGS

Initial estimates relied primarily on equations that incorporated factors known to influence creatinine concentrations such as age, sex and anthropometric measures. More recent estimates of glomerular filtration rate have replaced the anthropometric measures with the social construct of race, suggesting that glomerular filtration rates for black individuals are higher at the same concentration of creatinine. This approach has led to large variations in the estimated differences in glomerular filtration rate between black and nonblack individuals in the United States that have not been reproducible, resulting in a plethora of population-specific formulae across the country.

SUMMARY

The introduction of race in estimated glomerular filtration rate equations may have potential unintended negative consequences for the very population with the greatest burden of kidney disease. These potential disadvantages underscore the need to perhaps return to the replacement of race with more objective anthropometric measures without the loss of precision.

Methods and reporting of kidney function: a systematic review of studies from sub-Saharan Africa

Globally, chronic kidney disease (CKD) is an emerging public health challenge but accurate data on its true prevalence are scarce, particularly in poorly resourced regions such as sub-Saharan Africa (SSA). Limited funding for population-based studies, poor laboratory infrastructure and the absence of a validated estimating equation for kidney function in Africans are contributing factors. Consequently, most available studies used to estimate population prevalence are hospital-based, with small samples of participants who are at high risk for kidney disease. While serum creatinine is most commonly used to estimate glomerular filtration, there is considerable potential bias in the measurement of creatinine that might lead to inaccurate estimates of kidney disease at individual and population level. To address this, the Laboratory Working Group of the National Kidney Disease Education Program published recommendations in 2006 to standardize the laboratory measurement of creatinine. The primary objective of this review was to appraise implementation of these recommendations in studies conducted in SSA after 2006. Secondary objectives were to assess bias relating to choice of estimating equations for assessing glomerular function in Africans and to evaluate use of recommended diagnostic criteria for CKD. This study was registered with Prospero (CRD42017068151), and using PubMed, African Journals Online and Web of Science, 5845 abstracts were reviewed and 252 full-text articles included for narrative analysis. Overall, two-thirds of studies did not report laboratory methods for creatinine measurement and just over 80% did not report whether their creatinine measurement was isotope dilution mass spectroscopy (IDMS) traceable. For those reporting a method, Jaffe was the most common (93%). The four-variable Modification of Diet in Renal Disease (4-v MDRD) equation was most frequently used (42%), followed by the CKD Epidemiology Collaboration (CKD-EPI) equation for creatinine (26%). For the 4-v MDRD equation and CKD-EPI equations, respectively, one-third to one half of studies clarified use of the coefficient for African-American (AA) ethnicity. When reporting CKD prevalence, <15% of studies fulfilled Kidney Disease: Improving Global Outcomes criteria and even fewer used a population-based sample. Six studies compared performance of estimating equations to measured glomerular filtration rate (GFR) demonstrating that coefficients for AA ethnicity used in the 4-v MDRD and the CKD-EPI equations overestimated GFR in Africans. To improve on reporting in future studies, we propose an ‘easy to use’ checklist that will standardize reporting of kidney function and improve the quality of studies in the region. This research contributes some understanding of the factors requiring attention to ensure accurate assessment of the burden of kidney disease in SSA. Many of these factors are difficult to address and extend beyond individual researchers to health systems and governmental policy, but understanding the burden of kidney disease is a critical first step to informing an integrated public health response that would provide appropriate screening, prevention and management of kidney disease in countries from SSA. This is particularly relevant as CKD is a common pathway in both infectious and non-communicable diseases, and multimorbidity is now commonplace, and even more so when those living with severe kidney disease have limited or no access to renal replacement therapy.

Screening for chronic kidney disease in rural Malawi: results from a diabetic clinic

Objective

Patients with diabetes are at high risk of developing renal insufficiency and chronic kidney disease (CKD). As a result, screening for CKD is essential in diabetic patients as part of their care. This study investigated the prevalence of renal insufficiency, CKD, and correlates of CKD in diabetic patients attending Integrated Chronic Care Clinics in Neno District, Malawi.

Results

Of 203 diabetic patients, 148 (73%) were screened for CKD by measurement of serum creatinine and urinary protein between April 2016 and January 2019. 39.2% (n = 58) of the patients had abnormal estimated glomerular filtration rate (eGFR), as estimated by CKD Epidemiology Collaboration formula and/or ≥ 2+ urine protein. 13.5% (95% CI 8.4–20.0%, 20/148) of the patients had renal insufficiency based on eGFR of less than 60 ml/min/1.73 m². 8.8% (95% CI 4.8–14.6%, 13/148) had CKD based on eGFR of less than 60 ml/min/1.73 m² measured twice at least 3 months apart. In bivariate analysis, CKD was associated with older age, high systolic blood pressure and lower fasting blood sugar. Despite the low sample size, the study showed a moderately high prevalence of renal insufficiency and CKD in a rural cohort of diabetic patients in Malawi.

Prevalence of impaired renal function among rural and urban populations: findings of a cross-sectional study in Malawi

Background: Sub-Saharan Africa faces region-specific risk factors for chronic kidney disease (CKD), such as nephrotoxic herbal medicines, antiretroviral therapy and infections, in addition to hypertension and diabetes. However, large epidemiological studies from this area are scarce. Methods: In a cross-sectional survey of non-communicable diseases, we conducted a prevalence sub-study of CKD in two Malawian populations. Study participants (N=5264) of 18 years of age and above were recruited and data on demographics and CKD risk factors were collected. Glomerular filtration rate was estimated (eGFR) using the CKD-EPI equation. Results: The prevalence of eGFR<60ml/min/1.73m 2 was 1.4% (95% CI 1.1 - 1.7%) and eGFR<90ml/min/1.73m 2 was 20.6% (95% CI 19.5 - 21.7%). The rural area had higher age-standardized prevalence of both eGFR<60ml/min/1.73m 2, at 1.8% (95% CI 1.4 - 2.3) and eGFR <90 ml/min/1.73m², at 21.1% (95% CI 19.9 - 22.3), than urban location, which had a prevalence of 1.5%, (95% CI 1.0 - 2.2) and 19.4% (95% CI 18.0 - 20.8), respectively, with overlapping confidence intervals. The prevalence of CKD was lower in females than in males in both rural and urban areas. Older age (p < 0.001), a higher level of education (p = 0.03) and hypertension (p < 0.001) were associated with a higher adjusted odds ratio (aOR) of low eGFR. Diabetes was associated with a reduced aOR of eGFR<90ml/min/1.73m 2 of 0.69 (95% CI 0.49-0.96; p=0.03). Of participants with eGFR<60ml/min/1.73m 2, 14 (19.4%) had no history of hypertension, diabetes or HIV, while 36 (50%) had a single risk factor of being hypertensive. Conclusion s: Impaired renal function is prevalent, but lower than expected, in rural and urban Malawi. Further research is needed to increase understanding of CKD incidence, survival and validation of eGFR calculations in this population.

Chronic kidney disease in the global adult HIV-infected population: A systematic review and meta-analysis

INTRODUCTION

The widespread use of antiretroviral therapies (ART) has increased life expectancy in HIV patients, predisposing them to chronic non-communicable diseases including Chronic Kidney Disease (CKD). We performed a systematic review and meta-analysis (PROSPERO registration number CRD42016036246) to determine the global and regional prevalence of CKD in HIV patients.

METHODS

We searched PubMed, Web of Science, EBSCO and AJOL for articles published between January 1982 and May 2016. CKD was defined as estimated glomerular filtration rate (eGFR) <60ml/min using the MDRD, Cockcroft-Gault or CKD-EPI equations. Random effects model was used to combine prevalence estimates from across studies after variance stabilization via Freeman-Tukey transformation.

RESULT

Sixty-one eligible articles (n = 209,078 HIV patients) in 60 countries were selected. The overall CKD prevalence was 6.4% (95%CI 5.2-7.7%) with MDRD, 4.8% (95%CI 2.9-7.1%) with CKD-EPI and 12.3% (95%CI 8.4-16.7%) with Cockcroft-Gault; p = 0.003 for difference across estimators. Sub-group analysis identified differences in prevalence by WHO region with Africa having the highest MDRD-based prevalence at 7.9% (95%CI 5.2-11.1%). Within Africa, the pooled MDRD-based prevalence was highest in West Africa [14.6% (95%CI 9.9-20.0%)] and lowest in Southern Africa (3.2%, 95%CI 3.0-3.4%). The heterogeneity observed could be explained by WHO region, comorbid hypertension and diabetes mellitus, but not by gender, hepatitis B or C coinfection, CD4 count or antiretroviral status.

CONCLUSION

CKD is common in HIV-infected people, particularly in Africa. HIV treatment programs need to intensify screening for CKD with added need to introduce global guidelines for CKD identification and treatment in HIV positive patients.

Prevalence and burden of chronic kidney disease among the general population and high-risk groups in Africa: a systematic review

OBJECTIVES

While increasing attention is paid to the rising prevalence of chronic diseases in Africa, there is little focus on chronic kidney disease (CKD). This systematic review assesses CKD burden among the general population and high-risk groups on the entire African continent.

DESIGN, SETTING AND PARTICIPANTS

We searched Medline and PubMed databases for articles published between 1 January 1995 and 7 April 2017 by sensitive search strategies focusing on CKD surveys at the community level and high-risk groups. In total, 7918 references were evaluated, of which 7766 articles were excluded because they did not meet the inclusion criteria. Thus, 152 studies were included in the final analysis.

OUTCOME MEASUREMENT

The prevalence of CKD in each study group was expressed as a range and pooled prevalence rate of CKD was calculated as a point estimate and 95% CI. No meta-analysis was done. Data were presented for different populations.

RESULTS

In the community-level studies, based on available medium-quality and high-quality studies, the prevalence of CKD ranged from 2% to 41% (pooled prevalence: 10.1%; 95% CI 9.8% to 10.5%). The prevalence of CKD in the high-risk groups ranged from 1% to 46% (pooled prevalence: 5.6%; 95% CI 5.4% to 5.8%) in patients with HIV (based on available medium-quality and high-quality studies), 11%-90% (pooled prevalence: 24.7%; 95% CI 23.6% to 25.7%) in patients with diabetes (based on all available studies which are of low quality except four of medium quality) and 13%-51% (pooled prevalence: 34.5%; 95 % CI 34.04% to 36%) in patients with hypertension (based on all available studies which are of low quality except two of medium quality).

CONCLUSION

In Africa, CKD is a public health problem, mainly attributed to high-risk conditions as hypertension and diabetes. The poor data quality restricts the validity of the findings and draws the attention to the importance of designing future robust studies.

Impact of the estimation equation for GFR on population-based prevalence estimates of kidney dysfunction

Background

Estimating equations are recommended by clinical guidelines as the preferred method for assessment of glomerular filtration rate (GFR). The aim of the study was to compare population-based prevalence estimates of decreased kidney function in Germany defined by an estimated GFR (eGFR) <60 ml/min/1.73m² using different equations.

Methods

The study included 7001 participants of the German Health Interview and Examination Survey for Adults 2008–2011 (DEGS1) for whom GFR was estimated using the Modification of Diet in Renal Disease study equation (MDRD), the revised Lund-Malmö equation (LM), the Full Age Spectrum creatinine equation (FAScre), the Chronic Kidney Disease Epidemiology Collaboration equations with creatinine and cystatin C (CKD-EPIcrecys), with creatinine (CKD-EPIcre) and with cystatin C (CKD-EPIcys). Bland-Altman plots were used to evaluate the agreement between the equations.

Results

Prevalence estimates of decreased kidney function were: 2.1% (CKD-EPIcys), 2.3% (CKD-EPIcrecys), 3.8% (CKD-EPIcre), 5.0% (MDRD), 6.0% (LM) and 6.9% (FAScre). The systematic differences between the equations were smaller by comparing either equations that include serum cystatin C or equations that include serum creatinine alone and increased considerably by increasing eGFR.

Conclusions

Prevalence estimates of decreased kidney function vary considerably according to the equation used for estimating GFR. Equations that include serum cystatin C provide lower prevalence estimates if compared with equations based on serum creatinine alone. However, the analysis of the agreement between the equations according to eGFR provides evidence that the equations may be used interchangeably among persons with pronounced decreased kidney function. The study illustrates the implications of the choice of the estimating equation in an epidemiological setting.

Electronic supplementary material

The online version of this article (10.1186/s12882-017-0749-5) contains supplementary material, which is available to authorized users.

Assessment of renal function in routine care of people living with HIV on ART in a resource-limited setting in urban Zambia

Introduction

Data on renal impairment in sub-Saharan Africa (SSA) remains scarce, determination of renal function is not part of routine assessments. We evaluated renal function and blood pressure in a cohort of people living with HIV (PLWH) on antiretroviral treatment (ART) in the Renal Care Zambia project (ReCaZa).

Methods

Using routine data from an HIV outpatient clinic from 2011–2013, we retrospectively estimated the glomerular filtration rate (eGFR, CKD-Epi formula) of PLWH on ART in Lusaka, Zambia. Data were included if adults had had at least one serum creatinine recorded and had been on ART for a minimum of three months. We investigated the differences in eGFR between ART subgroups with and without tenofovir disproxil fumarate (TDF), and applied multivariable linear models to associate ART and eGFR, adjusted for eGFR before ART initiation.

Results and discussion

Among 1118 PLWH (63,3% female, mean age 41.8 years, 83% ever on TDF; median duration 1461 [range 98 to 4342] days) on ART, 28.3% had an eGFR <90 ml/min, and 5.5% <60 ml/min at their last measurement. Information on other conditions associated with renal impairment was not systematically documented. Fourteen per cent of the PLWH who later switched to TDF-free ART had an initial eGFR lower 60ml/min. Nineteen percent had first-time hypertensive readings at their last visit. The multivariable models suggest that physicians acted according to guidelines and replaced TDF-containing ART if patients developed moderate/severe renal impairment.

Conclusions

Assessment of renal function in SSA remains a challenge. The vast majority of PLWH benefit from long-term ART, including improved renal function. However, approximately 5% of PLWH on ART may have clinically relevant decreased eGFR, and 27% hypertension. While a routine renal assessment might not be feasible, strategies to identify patients at risk are warranted. Targeted monitoring prior and during ART is recommended, however, should not delay ART access.

The global burden of chronic kidney disease: estimates, variability and pitfalls

Chronic kidney disease (CKD) is currently defined by abnormalities of kidney structure or function assessed using a matrix of variables - including glomerular filtration rate (GFR), thresholds of albuminuria and duration of injury - and is considered by many to be a common disorder globally. However, estimates of CKD prevalence vary widely, both within and between countries. The reasons for these variations are manifold, and include true regional differences in CKD prevalence, vagaries of using estimated GFR (eGFR) for identifying CKD, issues relating to the use of set GFR thresholds to define CKD in elderly populations, and concerns regarding the use of one-off testing for assessment of eGFR or albuminuria to define the prevalence of CKD in large-scale epidemiological studies. Although CKD is common, the suggestion that its prevalence is increasing in many countries might not be correct. Here, we discuss the possible origins of differences in estimates of CKD prevalence, and present possible solutions for tackling the factors responsible for the reported variations in GFR measurements. The strategies we discuss include approaches to improve testing methodologies for more accurate assessment of GFR, to improve awareness of factors that can alter GFR readouts, and to more accurately stage CKD in certain populations, including the elderly.

The prevalence of renal impairment in individuals seeking HIV testing in Urban Malawi

BACKGROUND

Chronic kidney disease (CKD) poses a major health threat to people living in low- and middle-income countries, especially when it is combined with HIV, antiretroviral treatment (ART) or communicable and non-communicable diseases. Data about the prevalence of CKD and its association with other diseases is scarce, particularly in HIV-negative individuals. This study estimated the prevalence of CKD in individuals who were either HIV-positive (and ART-naïve) or HIV-negative in an urban Malawian population.

METHODS

This cross-sectional study was conducted at a HIV Testing and Counselling Centre in Lilongwe, Malawi. Consecutive clients who were ≥18 years and consented to participate were enrolled over a 3-month period. Clients were screened for potential renal disease and other conditions. Their blood pressure was measured, urine examined via dipstick and albumin/creatinine ratio and blood drawn for creatinine, cystatin C and sero-markers for schistosomiasis. Estimated glomerular filtration (eGFR) rate was calculated using a cystatin C-based formula and classified according to the matching CKD stages by K/DOQI (The National Kidney Foundation Kidney Disease Outcome Quality Initiative). We performed a descriptive analysis and compared differences between HIV-positive (and ART naïve) and -negative participants.

RESULTS

Out of 381 consecutive clients who were approached between January and March 2012, 366 consented and 363 (48% female; 32% HIV-positive) were included in the analysis. Reasons for exclusion were missing samples or previous use of ART. HIV-positive and negative clients did not differ significantly with regard to age, sex or medical history, but they did differ for BMI-21.3 (±3.4) vs. 24 (±5.1), respectively (p < 0.001). Participants also differed with regard to serum cystatin C levels, but not creatinine. Reduced kidney function (according to CKD stages 2-5) was significantly more frequent 15.5 vs. 3.6%, respectively (p < 0.001) among HIV-positive clients compared to the HIV-negative group. Differences in renal function were most pronounced in the eGFR range 60-89 ml/min/1.73 m2 accompanied by proteinuria with results as 11.2% vs. 1.2%, respectively for clients who were HIV-positive vs. HIV-negative (p = 0.001).

CONCLUSIONS

Reduced glomerular filtration and/or proteinuria occurred in 15.5% of HIV-positive, and 3.6% of HIV-negative patients in this urban Malawian cohort. Since generalized renal monitoring is not feasible in Malawi or other resource-limited countries, strategies to identify patients at risk for higher stages of CKD and appropriate preventive measures are needed for both HIV-positive and HIV-negative patients.