Baumann, N

Abstract BACKGROUND The Kidney Disease Improving Global Outcomes (KDIGO) guideline recommends use of a cystatin C–based estimated glomerular filtration rate (eGFR) to confirm creatinine-based eGFR between 45 and 59 mL · min−1 · (1.73 m2)−1. Prior studies have demonstrated that comorbidities such as solid-organ transplant strongly influence the relationship between measured GFR, creatinine, and cystatin C. Our objective was to evaluate the performance of cystatin C–based eGFR equations compared with creatinine-based eGFR and measured GFR across different clinical presentations. METHODS We compared the performance of the CKD-EPI 2009 creatinine-based estimated GFR equation (eGFRCr) and the newer CKD-EPI 2012 cystatin C–based equations (eGFRCys and eGFRCr-Cys) with measured GFR (iothalamate renal clearance) across defined patient populations. Patients (n = 1652) were categorized as transplant recipients (n = 568 kidney; n = 319 other organ), known chronic kidney disease (CKD) patients (n = 618), or potential kidney donors (n = 147). RESULTS eGFRCr-Cys showed the most consistent performance across different clinical populations. Among potential kidney donors without CKD [stage 2 or higher; eGFR >60 mL · min−1 · (1.73 m2)−1], eGFRCys and eGFRCr-Cys demonstrated significantly less bias than eGFRCr; however, all 3 equations substantially underestimated GFR when eGFR was <60 mL · min−1 · (1.73 m2)−1. Among transplant recipients with CKD stage 3B or greater [eGFR <45 mL · min−1 · (1.73 m2)−1], eGFRCys was significantly more biased than eGFRCr. No clear differences in eGFR bias between equations were observed among known CKD patients regardless of eGFR range or in any patient group with a GFR between 45 and 59 mL · min−1 · (1.73 m2)−1. CONCLUSIONS The performance of eGFR equations depends on patient characteristics that are readily apparent on presentation. Among the 3 CKD-EPI equations, eGFRCr-Cys performed most consistently across the studied patient populations.

Objective To evaluate whether genetic correction using the genetic variants prostate‐specific antigen ( PSA )‐single nucleotide polymorphisms ( SNPs ) could reduce potentially unnecessary and/or delayed biopsies in A frican‐ A merican men. Subjects and Methods We compared the genotypes of four PSA ‐ SNPs between 964 C aucasian and 363 A frican‐ A merican men without known prostate cancer ( PCa ). We adjusted the PSA values based on an individual's PSA‐SNP carrier status, and calculated the percentage of men that would meet commonly used PSA thresholds for biopsy (≥2.5 or ≥4.0 ng/mL) before and after genetic correction. Potentially unnecessary and delayed biopsies were defined as those men who were below and above the biopsy threshold after genetic correction, respectively. Results Overall, 349 (96.1%) and 354 (97.5%) A frican‐ A merican men had measured PSA levels <2.5 and <4.0 ng/mL. Genetic correction in A frican‐ A merican men did not avoid any potentially unnecessary biopsies, but resulted in a significant ( P < 0.001) reduction in potentially delayed biopsies by 2.5% and 3.9%, based on the biopsy threshold level. Conclusions There are significant differences in the influence of the PSA ‐ SNPs between A frican‐ A merican and C aucasian men without known PCa , as genetic correction resulted in an increased proportion of A frican‐ A merican men crossing the threshold for biopsy. These results raise the question of whether genetic differences in PSA might contribute to delayed PCa diagnosis in A frican‐ A merican men.