POS-233 COMPARISON OF GLOMERULAR FILTRATION RATE EQUATIONS IN A RURAL NEW MEXICO COHORT

Abstract

Estimated glomerular filtration rate (eGFR) equations use plasma filtration markers to predict kidney function. There are scarce data regarding the performance of various eGFR equations in Indigenous and Hispanic populations. Serum creatinine (SCr) has been historically used to estimate eGFR, but Cystatin C (CysC) and beta-2 microglobulin (B2M) may have less inter-person variability based on muscle mass, age and gender. We hypothesized that the various SCr, CysC or B2M-based eGFR equations will evaluate kidney function differently among Hispanics and Native Americans residing in rural New Mexico (NM). We studied 210 participants from the Community-Based Study of the Epidemiology of Chronic Kidney Disease (CKD) in Cuba, NM and Surrounding Areas (COMPASS). At study enrollment clinical measurements, questionnaires and serum blood specimens were obtained. Samples were analyzed at University of New Mexico’s Clinical Translational Sciences Center and TriCore Reference Laboratories. The method comparison between three eGFR equations was tested using Bland-Altman plots. Participants were racially diverse (American Indian 31.43%), but predominantly white (39.05%), Hispanic (53.81%), women (61.43%) and overweight (BMI 30.29 ± 6.84) (see Table below). The mean difference between CysC-eGFR and SCr-eGFR was 25.4 ml/min/1.73m2, and that between CysC-eGFR and B2M-eGFR was 25.3 ml/min/1.73m2. Agreement between CysC-eGFR and B2M-eGFR was excellent, with a mean difference of -0.12 ml/min/1.73m2 (Figure). Tabled 1Characteristics of Study PopulationSummary (Number of Participants = 210)Age49.80 ± 17.86GenderMales81 (38.57 %)Females129 (61.43 %)EthnicityHispanic or Latino113 (53.81 %)Not Hispanic or Latino96 (45.71 %)Unknown/not reported1 (0.48 %)RaceAmerican Indian/Alaska Natives66 (31.43 %)More than one race6 (2.86 %)Unknown/Not reported56 (26.67 %)White82 (39.05 %)Highest Degree of EducationK-1245 (21.43 %)High School degree87 (41.43 %)Higher than High School degree77 (36.66 %)Not disclosed1 (0.48 %)Health Insurance TypeMedicare34 (16.19 %)Medicaid52 (24.76 %)Other51 (24.29 %)2+ type of insurance55 (26.19 %)Uninsured/not disclosed18 (8.57 %)Blood Pressure (BP)Mean ± stdSystolic BP127 ± 14Diastolic BP77 ± 11Laboratory Values (serum)Body Mass Index (BMI)30.29 ± 6.84Serum glucose levels (mg/dL)121.27 ± 58.84Hemoglobin A1C (%)6.2% ± 0.02Serum Creatinine (mg/dL)0.9 ± 0.25Cystatin C (mg/L)0.72 ± 0.35High Sensitivity C-Reactive Protein (mg/L)4.97 ± 6.47BUN (mg/dL)13.83 ± 4.92Albumin (mg/dL)4.20 ± 0.36Hemoglobin (gm/dL)15.01 ± 1.56Hematocrit (%)44.63 ± 3.96Phosphorous (mg/dL)3.4 ± 0.68Uric Acid (mg/dL)5.12 ± 1.33Calcium (mg/dL)9.51 ± 0.53 Open table in a new tab View Large Image Figure ViewerDownload Hi-res image Download (PPT) As the replacement of race-adjusted, SCr-eGFR with CysC-eGFR gains momentum, it is important to understand potential analytical biases introduced by CysC in other racial and ethnic groups. B2M-eGFR does not require adjustment for age, race, or gender thus may be a more optimal method to calculate GFR. Further studies with objective measurements of kidney function are needed to validate these findings.