BIS1 Equations Research Articles

Estimación del filtrado glomerular en personas mayores de 85 años: comparación de las ecuaciones CKD-EPI, MDRD-IDMS y BIS1

BackgroundThe evidence of glomerular filtration rate (GFR) estimating with serum creatinine based formulae in the elderly population is scarce. The purpose of this study is to compare CKD-EPI, MRD4-IDMS and BIS1 equations to analyse correlation and concordance in a population older than 85 years old. Patients and methodsWe designed a retrospective cross-sectional study, which included data from 600 patients older than 85 years. GFR was estimated by the following equations: CKD-EPI, MDR4-IDMS and BIS1, using as variables sex, age and serum creatinine concentration. Statistics analysis included Wilcoxon test, Bland-Altman plot, non-parametric Passing-Bablok method and kappa statistic (simple and weighted). ResultsThe patients’ median (range) age was 87 (interval 85-98). The median GFR (range) was 42.4 (5.2-127.4) mL/min/1.73 m2, when it was estimated with MDRD-IDMS, 40.0 (4.5-93.1) for CKD-EPI and 36.9 (7.6-83.7) for BIS1. The comparison of BIS1 and CKD-EPI and MDRD-IDMS using the Wilcoxon test was significant (P<.001). The regression analysis yielded the following equations: MDRD-IDMS= 1,025×CKD-EPI+1.360; BIS1= 0.688×CKD-EPI+9.074 and BIS1= 0.666×MDRD-IDMS+8.401. The weighted coefficient was 0.958 for the concordance between MDRD-IDMS and CKD-EPI, 0.812 for the concordance between MDRD-IDMS and BIS1 and 0.846 for CKD-EPI and BIS1. ConclusionsThe GFR estimations obtained with BS1 equation are not interchangeable with MDRD-IDMS or CKD-EPI equations. BIS1 estimates lower GFR values than MDRD-IDMS and CKD-EPI and tends to classify the patients in a more advanced chronic kidney disease stage, especially for estimated GFR higher than 29mL/min/1.73 m2.

Kidney Function Decline and Apparent Treatment-Resistant Hypertension in the Elderly.

BackgroundCross-sectional studies show a strong association between chronic kidney disease and apparent treatment-resistant hypertension, but the longitudinal association of the rate of kidney function decline with the risk of resistant hypertension is unknown.MethodsThe population-based Three-City included 8,695 participants older than 65 years, 4265 of them treated for hypertension. We estimated the odds ratios (OR) of new-onset apparent treatment-resistant hypertension, defined as blood pressure ≥ 140/90 mmHg despite use of 3 antihypertensive drug classes or ≥ 4 classes regardless of blood pressure, associated with the mean estimated glomerular filtration rate (eGFR) level and its rate of decline over 4 years, compared with both controlled hypertension and uncontrolled nonresistant hypertension with ≤ 2 drugs. GFR was estimated with three different equations.ResultsBaseline prevalence of apparent treatment-resistant hypertension and of controlled and uncontrolled nonresistant hypertension, were 6.5%, 62.3% and 31.2%, respectively. During follow-up, 162 participants developed apparent treatment-resistant hypertension. Mean eGFR decline with the MDRD equation was 1.5±2.9 mL/min/1.73 m² per year: 27.7% of the participants had an eGFR ≥3 and 10.1% ≥ 5 mL/min/1.73 m² per year. After adjusting for age, sex, obesity, diabetes, and cardiovascular history, the ORs for new-onset apparent treatment-resistant hypertension associated with a mean eGFR level, per 15 mL/min/1.73m² drop, were 1.23 [95% confidence interval 0.91–1.64] compared to controlled hypertension and 1.10 [0.83–1.45] compared to uncontrolled nonresistant hypertension; ORs associated with a decline rate ≥ 3 mL/min/1.73m² per year were 1.89 [1.09–3.29] and 1.99 [1.19–3.35], respectively. Similar results were obtained when we estimated GFR with the CKDEPI and the BIS1 equations. ORs tended to be higher for an eGFR decline rate ≥ 5 mL/min/1.73m² per year.ConclusionThe speed of kidney function decline is associated more strongly than kidney function itself with the risk of apparent treatment-resistant hypertension in the elderly.

An efficient approach for glomerular filtration rate assessment in older adults

Assessment of glomerular filtration rate (GFR) is crucial because the GFR value defines the stage of chronic kidney disease and determines the adjustment of drug dosage. The aim was to investigate a new method for the accurate determination of GFR in older adults based on the combination of an exogenous filtration marker, iohexol, and an endogenous marker, serum creatinine or cystatin C. We combined variables for the estimation of GFR with a reduced set of measurements of the marker iohexol. In a population-based sample of 570 subjects (≥70 years old) from the Berlin Initiative Study (BIS), we investigated the following: (i) the BIS1 and BIS2 equations based on age, gender and serum creatinine with or without serum cystatin C; (ii) equations based on one or two iohexol measurements; and (iii) equations based on the combination of variables from BIS1 or BIS2 with iohexol measurements. The reference standard was based on eight iohexol measurements. The cut-off value of 60 ml min(-1) (1.73 m)(-2) was chosen to assess accuracy. Equations were constructed using a learning sample (n = 285) and an independent validation sample (n = 285). Misclassification rates were 17.2% (BIS1), 11.6% (BIS2), 14.7% [iohexol measurement at 240 min (iohexol240 )], 7.0% (iohexol240 combined with variables included in BIS1) and 6.7% (iohexol240 combined with variables included in BIS2). Misclassification rates did not decrease significantly after inclusion of two or three iohexol measurements. Combined strategies for the determination of GFR lead to a relevant increase of diagnostic validity.

Assessment of glomerular filtration rate in elderly patients with chronic kidney disease

We sought to evaluate various glomerular filtration rate (GFR) estimating equations in elderly patients with chronic kidney disease (CKD). A total of 332 Chinese elderly patients with CKD who had undergone technetium-99m diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) renal dynamic imaging were enrolled. The MDRD equation, the re-expressed MDRD equation, the Chinese equation, the Ruijin equation, the previously Japanese equation, the new Japanese equation, the CKD-EPI equation, and the BIS1 equation were compared. The median of difference between estimated GFR and standard GFR ranged from -9.78 to 1.79 ml/min/1.73 m(2). The interquartile range of difference ranged from 12.38 to 20.87 ml/min/1.73 m(2). Accuracy with a deviation <30 % ranged from 44.9 to 66.3 %. However, none of the equations had accuracy up to the 70 % level. Bland-Altman analysis demonstrated that the precision ranged from 50.5-87.6 ml/min/1.73 m(2). The slopes of regression line ranged from -0.26 to 0.55 and the intercepts ranged from -18.71 to 11.07. In both the overall performance and the performances in different stage of CKD, GFR estimated by the BIS1 equation performed better results. None of the GFR estimating equations are suitable for the specific Chinese population tested. At present, the BIS1 equation may be the optimal one for elderly Chinese CKD patients.

Performance of creatinine-based equations compared in older patients

The current equations for estimating glomerular filtration rate (GFR) have limited precision in older people. The Berlin Initiative Study (BIS-1) equation has recently been developed to improve the precision and accuracy of GFR estimation in older people, over the previous simplified Modification of Diet in Renal Disease (MDRD) Study and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. The study included 224 white patients aged >70 years who had simultaneous measurements of plasma creatinine and renal clearance of inulin. Creatinine assays used an enzymatic method with calibrators defined by isotope dilution mass spectrometry. The performance of BIS-1, MDRD and CKD-EPI equations in estimating GFR were compared. BIS-1 was the most accurate: the percentage of GFR estimates that fell within the range of measured GFR ± 30% (P30) was 75.56% vs. 70.67% with MDRD and 72% with CKD-EPI. BIS-1 had the lowest median bias: (interquartile range) (4.1 (11.4) vs 5.8 (12.7) and 5.4 (12.8) respectively) the highest precision (the SD of the estimated GFR minus measured GFR differences was 9.21 vs 12.78 and 10.83 mL/min/1.73 m² respectively) and the highest concordance correlation coefficient (CCC) (0.82 vs. 0.74 and 0.79 respectively, p<0.05). However, in chronic kidney disease (CKD) stages 4 and 5, the CKD-EPI equation had the highest P30, the lowest median bias and the highest CCC: it was more accurate than the BIS-1 equation. Among the 3 creatinine-based equations compared, BIS-1 was the most reliable for assessing renal function in older white patients, especially in those with CKD stages 1 to 3.

Two Novel Equations to Estimate Kidney Function in Persons Aged 70 Years or Older

In older adults, current equations to estimate glomerular filtration rate (GFR) are not validated and may misclassify elderly persons in terms of their stage of chronic kidney disease. To derive the Berlin Initiative Study (BIS) equation, a novel estimator of GFR in elderly participants. Cross-sectional. Data were split for analysis into 2 sets for equation development and internal validation. Random community-based population of a large insurance company. 610 participants aged 70 years or older (mean age, 78.5 years). Iohexol plasma clearance measurement as gold standard. GFR, measured as the plasma clearance of the endogenous marker iohexol, to compare performance of existing equations of estimated GFR with measured GFR of the gold standard; estimation of measured GFR from standardized creatinine and cystatin C levels, sex, and age in the learning sample; and comparison of the BIS equations (BIS1: creatinine-based; BIS2: creatinine- and cystatin C-based) with other estimating equations and determination of bias, precision, and accuracy in the validation sample. The new BIS2 equation yielded the smallest bias followed by the creatinine-based BIS1 and Cockcroft-Gault equations. All other equations considerably overestimated GFR. The BIS equations confirmed a high prevalence of persons older than 70 years with a GFR less than 60 mL/min per 1.73 m2 (BIS1, 50.4%; BIS2, 47.4%; measured GFR, 47.9%). The total misclassification rate for this criterion was smallest for the BIS2 equation (11.6%), followed by the cystatin C equation 2 (15.1%) proposed by the Chronic Kidney Disease Epidemiology Collaboration. Among the creatinine-based equations, BIS1 had the smallest misclassification rate (17.2%), followed by the Chronic Kidney Disease Epidemiology Collaboration equation (20.4%). There was no validation by an external data set. The BIS2 equation should be used to estimate GFR in persons aged 70 years or older with normal or mild to moderately reduced kidney function. If cystatin C is not available, the BIS1 equation is an acceptable alternative. Kuratorium für Dialyse und Nierentransplatation (KfH) Foundation of Preventive Medicine.