Bakhtawar K. Mahmoodi

Comparison of risk prediction using the CKD-EPI equation and the MDRD Study equation for estimated glomerular filtration rate

CONTEXT The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation more accurately estimates glomerular filtration rate (GFR) than the Modification of Diet in Renal Disease (MDRD) Study equation using the same variables, especially at higher GFR, but definitive evidence of its risk implications in diverse settings is lacking. OBJECTIVE To evaluate risk implications of estimated GFR using the CKD-EPI equation compared with the MDRD Study equation in populations with a broad range of demographic and clinical characteristics. DESIGN, SETTING, AND PARTICIPANTS A meta-analysis of data from 1.1 million adults (aged ≥ 18 years) from 25 general population cohorts, 7 high-risk cohorts (of vascular disease), and 13 CKD cohorts. Data transfer and analyses were conducted between March 2011 and March 2012. MAIN OUTCOME MEASURES All-cause mortality (84,482 deaths from 40 cohorts), cardiovascular mortality (22,176 events from 28 cohorts), and end-stage renal disease (ESRD) (7644 events from 21 cohorts) during 9.4 million person-years of follow-up; the median of mean follow-up time across cohorts was 7.4 years (interquartile range, 4.2-10.5 years). RESULTS Estimated GFR was classified into 6 categories (≥90, 60-89, 45-59, 30-44, 15-29, and <15 mL/min/1.73 m(2)) by both equations. Compared with the MDRD Study equation, 24.4% and 0.6% of participants from general population cohorts were reclassified to a higher and lower estimated GFR category, respectively, by the CKD-EPI equation, and the prevalence of CKD stages 3 to 5 (estimated GFR <60 mL/min/1.73 m(2)) was reduced from 8.7% to 6.3%. In estimated GFR of 45 to 59 mL/min/1.73 m(2) by the MDRD Study equation, 34.7% of participants were reclassified to estimated GFR of 60 to 89 mL/min/1.73 m(2) by the CKD-EPI equation and had lower incidence rates (per 1000 person-years) for the outcomes of interest (9.9 vs 34.5 for all-cause mortality, 2.7 vs 13.0 for cardiovascular mortality, and 0.5 vs 0.8 for ESRD) compared with those not reclassified. The corresponding adjusted hazard ratios were 0.80 (95% CI, 0.74-0.86) for all-cause mortality, 0.73 (95% CI, 0.65-0.82) for cardiovascular mortality, and 0.49 (95% CI, 0.27-0.88) for ESRD. Similar findings were observed in other estimated GFR categories by the MDRD Study equation. Net reclassification improvement based on estimated GFR categories was significantly positive for all outcomes (range, 0.06-0.13; all P < .001). Net reclassification improvement was similarly positive in most subgroups defined by age (<65 years and ≥65 years), sex, race/ethnicity (white, Asian, and black), and presence or absence of diabetes and hypertension. The results in the high-risk and CKD cohorts were largely consistent with the general population cohorts. CONCLUSION The CKD-EPI equation classified fewer individuals as having CKD and more accurately categorized the risk for mortality and ESRD than did the MDRD Study equation across a broad range of populations.

Associations of kidney disease measures with mortality and end-stage renal disease in individuals with and without hypertension

BACKGROUND Hypertension is the most prevalent comorbidity in individuals with chronic kidney disease. However, whether the association of the kidney disease measures, estimated glomerular filtration rate (eGFR) and albuminuria, with mortality or end-stage renal disease (ESRD) differs by hypertensive status is unknown. METHODS We did a meta-analysis of studies selected according to Chronic Kidney Disease Prognosis Consortium criteria. Data transfer and analyses were done between March, 2011, and June, 2012. We used Cox proportional hazards models to estimate the hazard ratios (HR) of mortality and ESRD associated with eGFR and albuminuria in individuals with and without hypertension. FINDINGS We analysed data for 45 cohorts (25 general population, seven high-risk, and 13 chronic kidney disease) with 1,127,656 participants, 364,344 of whom had hypertension. Low eGFR and high albuminuria were associated with mortality irrespective of hypertensive status in the general population and high-risk cohorts. All-cause mortality risk was 1·1-1·2 times higher in individuals with hypertension than in those without hypertension at preserved eGFR. A steeper relative risk gradient in individuals without hypertension than in those with hypertension at eGFR range 45-75 mL/min per 1·73 m(2) led to much the same mortality risk at lower eGFR. With a reference eGFR of 95 mL/min per 1·73 m(2) in each group to explicitly assess interaction, adjusted HR for all-cause mortality at eGFR 45 mL/min per 1·73 m(2) was 1·77 (95% CI 1·57-1·99) in individuals without hypertension versus 1·24 (1·11-1·39) in those with hypertension (p for overall interaction=0·0003). Similarly, for albumin-creatinine ratio of 300 mg/g (vs 5 mg/g), HR was 2·30 (1·98-2·68) in individuals without hypertension versus 2·08 (1·84-2·35) in those with hypertension (p for overall interaction=0·019). We recorded much the same results for cardiovascular mortality. The associations of eGFR and albuminuria with ESRD, however, did not differ by hypertensive status. Results for chronic kidney disease cohorts were similar to those for general and high-risk population cohorts. INTERPRETATION Chronic kidney disease should be regarded as at least an equally relevant risk factor for mortality and ESRD in individuals without hypertension as it is in those with hypertension. FUNDING US National Kidney Foundation.

High Absolute Risks and Predictors of Venous and Arterial Thromboembolic Events in Patients With Nephrotic Syndrome Results From a Large Retrospective Cohort Study

Background— No data are available on the absolute risk of either venous thromboembolism (VTE) or arterial thromboembolism (ATE) in patients with nephrotic syndrome. Reported risks are based on multiple case reports and small studies with mostly short-term follow-up. We assessed the absolute risk of VTE and ATE in a large, single-center, retrospective cohort study and attempted to identify predictive factors in these patients. Methods and Results— A total of 298 consecutive patients with nephrotic syndrome (59% men; mean age, 42±18 years) were enrolled. Mean follow-up was 10±9 years. Nephrotic syndrome was defined by proteinuria ≥3.5 g/d, and patients were classified according to underlying histological lesions accounting for nephrotic syndrome. Objectively verified symptomatic thromboembolic events were the primary study outcome. Annual incidences of VTE and ATE were 1.02% (95% confidence interval, 0.68 to 1.46) and 1.48% (95% confidence interval, 1.07 to 1.99), respectively. Over the first 6 months of follow-up, these rates were 9.85% and 5.52%, respectively. Proteinuria and serum albumin levels tended to be related to VTE; however, only the predictive value of the ratio of proteinuria to serum albumin was significant (hazard ratio, 5.6; 95% confidence interval, 1.2 to 26.2; P=0.03). In contrast, neither the degree of proteinuria nor serum albumin levels were related to ATE. Sex, age, hypertension, diabetes, smoking, prior ATE, and estimated glomerular filtration rate predicted ATE (P≤0.02). Conclusions— This study verifies high absolute risks of symptomatic VTE and ATE that were remarkably elevated within the first 6 months. Whereas the ratio of proteinuria to serum albumin predicted VTE, estimated glomerular filtration rate and multiple classic risk factors for atherosclerosis were predictors of ATE.

Microalbuminuria and Risk of Venous Thromboembolism

CONTEXT Microalbuminuria (albuminuria 30-300 mg per 24-hour urine collection) is a well-known risk marker for arterial thromboembolism. It is assumed that microalbuminuria reflects generalized endothelial dysfunction. Hence, microalbuminuria may also predispose for venous thromboembolism (VTE). OBJECTIVE To assess whether microalbuminuria is associated with VTE. DESIGN, SETTING, AND PARTICIPANTS Prevention of Renal and Vascular End-stage Disease (PREVEND) study, an ongoing community-based prospective cohort study initiated in 1997. All inhabitants of Groningen, The Netherlands, aged 28 through 75 years (n = 85,421) were sent a postal questionnaire and a vial to collect a first morning urine sample for measurement of urinary albumin concentration. Of those who responded (40,856), a cohort (8592 participants) including more participants with higher levels of urinary albumin concentration completed screening at an outpatient clinic. Screening data were collected on urinary albumin excretion (UAE) and risk factors for cardiovascular and renal disease. MAIN OUTCOME MEASURE Symptomatic and objectively verified VTE (ie, deep vein thrombosis, pulmonary embolism, or both) between study initiation and June 1, 2007. RESULTS Of 8574 evaluable participants (mean [SD] age, 49 [13] years; 50% men), 129 experienced VTE during a mean (SD) follow-up period of 8.6 (1.8) years, corresponding to overall annual incidence of 0.14% (95% confidence interval [CI], 0.11%-0.19%). Annual incidences were 0.12%, 0.20%, 0.40%, and 0.56% in participants with UAE of less than 15 (n = 6013), 15-29 (n = 1283), 30-300 (n = 1144), and greater than 300 (n = 134) mg per 24-hour urine collection, respectively (P for trend <.001). When adjusted for age, cancer, use of oral contraceptives, and atherosclerosis risk factors, hazard ratios associated with UAE levels of 15-29, 30-300, and greater than 300 mg/24 h were 1.40 (95% CI, 0.86-2.35), 2.20 (95% CI, 1.44-3.36), and 2.82 (95% CI, 1.21-6.61), respectively, compared with participants with UAE of less than 15 mg/24 h (global P = .001). Adjusted hazard ratio for microalbuminuria vs normoalbuminuria (UAE <30 mg/24 h) was 2.00 (95% CI, 1.34-2.98; P < .001). Microalbuminuria-related number needed to harm was 388 per year. CONCLUSION Microalbuminuria is independently associated with an increased risk for VTE.

Hereditary Deficiency of Protein C or Protein S Confers Increased Risk of Arterial Thromboembolic Events at a Young Age Results From a Large Family Cohort Study

Background— Whether hereditary protein S, protein C, or antithrombin deficiency is associated with arterial thromboembolism (ATE) and whether history of venous thromboembolism in these subjects predisposes them to subsequent ATE have yet to be determined. Methods and Results— On the basis of pedigree analysis, we enrolled a total of 552 subjects (52% women; mean age, 46±17 years), belonging to 84 different kindreds, in this retrospective family cohort study. Detailed information on previous episodes of venous thromboembolism, ATE, anticoagulant use, and atherosclerosis risk factors was collected. Primary study outcome was objectively verified symptomatic ATE. Of 552 subjects, 308 had protein S (35%), protein C (39%), or antithrombin (26%) deficiency. Overall, annual incidences of ATE were 0.34% (95% confidence interval [CI], 0.23 to 0.49) in deficient versus 0.17% (95% CI, 0.09 to 0.28) in nondeficient subjects; the hazard ratio was 2.3 (95% CI, 1.2 to 4.5). Because the risk hazards varied over lifetime, we performed a time-dependent analysis. After adjusting for atherosclerosis risk factors and clustering within families, we found that deficient subjects had a 4.7-fold (95% CI, 1.5 to 14.2; P=0.007) higher risk for ATE before 55 years of age versus 1.1 (95% CI, 0.5 to 2.6) thereafter compared with nondeficient family members. For separate deficiencies, the risks were 4.6- (95% CI, 1.1 to 18.3), 6.9- (95% CI, 2.1 to 22.2), and 1.1- (95% CI, 0.1 to 10.9) fold higher in protein S–, protein C–, and antithrombin-deficient subjects, respectively, before 55 years of age. History of venous thromboembolism was not related to subsequent ATE (hazard ratio, 1.1; 95% CI, 0.5 to 2.2). Conclusions— Compared with nondeficient family members, subjects with protein S or protein C deficiency but not antithrombin deficiency have a higher risk for ATE before 55 years of age that is independent of prior venous thromboembolism.

A prospective cohort study on the absolute risks of venous thromboembolism and predictive value of screening asymptomatic relatives of patients with hereditary deficiencies of protein S, protein C or antithrombin

See also Keeling D. Thrombophilia screening or screaming. This issue, pp 1191–2.

Association of Mild to Moderate Chronic Kidney Disease With Venous Thromboembolism Pooled Analysis of Five Prospective General Population Cohorts

Background— Recent findings suggest that chronic kidney disease (CKD) may be associated with an increased risk of venous thromboembolism (VTE). Given the high prevalence of mild-to-moderate CKD in the general population, in depth analysis of this association is warranted. Methods and Results— We pooled individual participant data from 5 community-based cohorts from Europe (second Nord-Trondelag Health Study [HUNT2], Prevention of Renal and Vascular End-stage Disease [PREVEND], and the Tromso study) and the United States (Atherosclerosis Risks in Communities [ARIC] and Cardiovascular Health Study [CHS]) to assess the association of estimated glomerular filtration rate (eGFR), albuminuria, and CKD with objectively verified VTE. To estimate adjusted hazard ratios for VTE, categorical and continuous spline models were fit by using Cox regression with shared-frailty or random-effect meta-analysis. A total of 1178 VTE events occurred over 599 453 person-years follow-up. Relative to eGFR 100 mL/min per 1.73 m2, hazard ratios for VTE were 1.29 (95% confidence interval, 1.04–1.59) for eGFR 75, 1.31 (1.00–1.71) for eGFR 60, 1.82 (1.27–2.60) for eGFR 45, and 1.95 (1.26–3.01) for eGFR 30 mL/min per 1.73 m2. In comparison with an albumin-to-creatinine ratio (ACR) of 5.0 mg/g, the hazard ratios for VTE were 1.34 (1.04–1.72) for ACR 30 mg/g, 1.60 (1.08–2.36) for ACR 300 mg/g, and 1.92 (1.19–3.09) for ACR 1000 mg/g. There was no interaction between clinical categories of eGFR and ACR ( P =0.20). The adjusted hazard ratio for CKD, defined as eGFR <60 mL/min per 1.73 m2 or albuminuria ≥30 mg/g, (versus no CKD) was 1.54 (95% confidence interval, 1.15–2.06). Associations were consistent in subgroups according to age, sex, and comorbidities, and for unprovoked versus provoked VTE, as well. Conclusions— Both eGFR and ACR are independently associated with increased risk of VTE in the general population, even across the normal eGFR and ACR ranges. # Clinical Perspective {#article-title-41}Background— Recent findings suggest that chronic kidney disease (CKD) may be associated with an increased risk of venous thromboembolism (VTE). Given the high prevalence of mild-to-moderate CKD in the general population, in depth analysis of this association is warranted. Methods and Results— We pooled individual participant data from 5 community-based cohorts from Europe (second Nord-Trøndelag Health Study [HUNT2], Prevention of Renal and Vascular End-stage Disease [PREVEND], and the Tromsø study) and the United States (Atherosclerosis Risks in Communities [ARIC] and Cardiovascular Health Study [CHS]) to assess the association of estimated glomerular filtration rate (eGFR), albuminuria, and CKD with objectively verified VTE. To estimate adjusted hazard ratios for VTE, categorical and continuous spline models were fit by using Cox regression with shared-frailty or random-effect meta-analysis. A total of 1178 VTE events occurred over 599 453 person-years follow-up. Relative to eGFR 100 mL/min per 1.73 m2, hazard ratios for VTE were 1.29 (95% confidence interval, 1.04–1.59) for eGFR 75, 1.31 (1.00–1.71) for eGFR 60, 1.82 (1.27–2.60) for eGFR 45, and 1.95 (1.26–3.01) for eGFR 30 mL/min per 1.73 m2. In comparison with an albumin-to-creatinine ratio (ACR) of 5.0 mg/g, the hazard ratios for VTE were 1.34 (1.04–1.72) for ACR 30 mg/g, 1.60 (1.08–2.36) for ACR 300 mg/g, and 1.92 (1.19–3.09) for ACR 1000 mg/g. There was no interaction between clinical categories of eGFR and ACR (P=0.20). The adjusted hazard ratio for CKD, defined as eGFR <60 mL/min per 1.73 m2 or albuminuria ≥30 mg/g, (versus no CKD) was 1.54 (95% confidence interval, 1.15–2.06). Associations were consistent in subgroups according to age, sex, and comorbidities, and for unprovoked versus provoked VTE, as well. Conclusions— Both eGFR and ACR are independently associated with increased risk of VTE in the general population, even across the normal eGFR and ACR ranges.

Association of Kidney Disease Measures With Ischemic Versus Hemorrhagic Strokes Pooled Analyses of 4 Prospective Community-Based Cohorts

Background and purpose— Although low glomerular filtration rate (GFR) and albuminuria are associated with increased risk of stroke, few studies compared their contribution to risk of ischemic versus hemorrhagic stroke separately. We contrasted the association of these kidney measures with ischemic versus hemorrhagic stroke. Methods— We pooled individual participant data from 4 community-based cohorts: 3 from the United States and 1 from The Netherlands. GFR was estimated using both creatinine and cystatin C, and albuminuria was quantified by urinary albumin-to-creatinine ratio (ACR). Associations of estimated GFR and ACR were compared for each stroke type (ischemic versus intraparenchymal hemorrhagic) using study-stratified Cox regression. Results— Among 29 595 participants (mean age, 61 [SD 12.5] years; 46% men; 17% black), 1261 developed stroke (12% hemorrhagic) during 280 549 person-years. Low estimated GFR was significantly associated with increased risk of ischemic stroke, but not hemorrhagic stroke, whereas high ACR was associated with both stroke types. Adjusted hazard ratios for ischemic and hemorrhagic stroke at estimated GFR of 45 (versus 95) mL/min per 1.73 m2 were 1.30 (95% confidence interval, 1.01–1.68) and 0.92 (0.47–1.81), respectively. In contrast, the corresponding hazard ratios for ACR of 300 (versus 5) mg/g were 1.62 (1.27–2.07) for ischemic and 2.57 (1.37–4.83) for hemorrhagic stroke, with significantly stronger association with hemorrhagic stroke (P=0.04). For hemorrhagic stroke, the association of elevated ACR was of similar magnitude as that of elevated systolic blood pressure. Conclusions— Whereas albuminuria showed significant association with both stroke types, the association of decreased estimated GFR was only significant for ischemic stroke. The strong association of albuminuria with both stroke types warrants clinical attention and further investigations.

Chronic kidney disease stages 1–3 increase the risk of venous thrombosis

Summary  Background: End‐stage renal disease has been associated with venous thrombosis (VT). However, the risk of VT in the early stages of chronic kidney disease (CKD) has not yet been investigated. The aim of this study was to investigate whether CKD patients with stage 1–3 disease are at increased risk of VT. Methods: Eight thousand four hundred and ninety‐five subjects were included in a prospective cohort study, in which renal function and albuminuria were assessed, starting in 1997–1998, and were followed for the occurrence of VT until 1 June 2007. CKD patients were staged according to the Kidney Disease Outcomes Quality Initiative guidelines, on the basis of 24‐h urine albumin excretion and estimated glomerular filtration rates. Objectively verified symptomatic VT was considered to be the endpoint. Results: Of the 8495 subjects, 243 had CKD stage 1, 856 CKD stage 2, and 491 CKD stage 3. During a median follow‐up period of 9.2 years, 128 individuals developed VT. The hazard ratios (HRs) for CKD stages 1, 2 and 3 were, respectively, 2.2 [95% confidence interval (CI) 0.9–5.1], 1.9 (95% CI 1.1–3.1) and 1.6 (95% CI 0.9–2.8) relative to those without CKD after adjustment for age, sex, body mass index, hypertension, diabetes, malignancy, and high‐sensitivity C‐reactive protein. Subjects with CKD stage 3 and albuminuria (≥ 30 mg d–1) had an adjusted HR of 3.0, and subjects with CKD stage 3 without albuminuria had an adjusted HR of 1.0. Conclusions: CKD stages 1 and 2, and CKD stage 3 in the presence of albuminuria, are risk factors for VT. The risk of VT is more related to albuminuria than to impaired glomerular filtration rate.

Statin use in patients with nephrotic syndrome is associated with a lower risk of venous thromboembolism

BACKGROUND Nephrotic syndrome (NS) is a well-known risk factor for venous thromboembolism (VTE), however preventive measures are not routinely taken. In non-renal populations, statins are associated with lower risk of VTE. Hence, we set up this single-center retrospective cohort study to assess whether statin use influenced VTE risk in NS subjects. METHODS We analyzed 289 consecutive patients with NS (defined by proteinuria ≥ 3.5 g/day) who were aged >18 years at the study entry and followed for at least 6 months. Use of statins and concomitant medication were determined. RESULTS Of patients with NS (59% men; mean age, 42 years), 48% used statins for at least 1 month during NS. Using univariate and time-dependent Cox regression analyses, hazard ratio for VTE in statin users versus non-users was 0.2 (95%CI, 0.1-0.7) and 0.6 (95% CI, 0.2 -2.0), respectively. Adjustments for potential confounders did not change outcomes. Three VTE events occurred in a total of 812 statin-years, corresponding to an annual incidence of 0.37% (95%CI, 0.12-1.15). In contrast, 17 VTE occurred in a total of 2106 patient-years without statin exposure, annual incidence 0.81% (95%CI, 0.50-1.30). CONCLUSIONS Although statistically significant, the hazard ratio of 0.2 for VTE risk in statin users versus non-users could have been biased, but the time-dependent hazard ratio of 0.6 was probably not. As the association was in the same direction for both analyses, we conclude that statin use is associated with a lower risk of VTE in patients with NS.