Larson, Timothy S.

Abstract Quantifying urine protein is critical for detecting and monitoring kidney disease. However, screens for proteinuria are unable to detect low levels of albuminuria. For this reason, our institution has long measured urinary total protein and osmolality on routine urinalysis specimens (RUS) and calculated a predicted 24-hour protein excretion (PER) based upon the protein to osmolality ratio (POR). Within the last decade, sodium-glucose cotransporter-2 inhibitors (SGLT2i) have been approved by the United States Food and Drug Administration (FDA) as a treatment for adults with type 2 diabetes mellitus, and these agents appear to be beneficial for many forms of proteinuric renal disease and confer renal protection. Therefore, we investigated whether the expected glucosuria and increase in urine osmolality while on SGLT2i would significantly alter the POR, and hence predicted PER, via a retrospective analysis of residual timed and randomly collected urine specimens. Between January 1st, 2014, until January 29th, 2025, 5820 patients with nearly contemporaneous (collected within one week of each other) timed collections and RUS were identified that included 5656 not on SGLT2i (Cohort A) and 164 patients prescribed SGLT2i (Cohort B). Total protein concentrations were assessed using a Roche Cobas c701 by using benzethonium chloride. The osmolality was determined via freezing point depression using a Precision Systems Inc Multi-OSMETTE, whereas glucose measurements were made using either an Arkray AX-4030 with AUTION Stick 9EB test strips or a Clinitek Status with Multistix 10 SG reagent strips. Predicted 24-hour protein results were then calculated from the POR using a published formula based upon prior clinical studies: 10(x·[log(protein/osmolality)]+y where x is 0.908 or 0.953 for males and females, respectively, and y is 2.8254 or 2.9739 for males and females, respectively. In Cohort A, there was good correlation between the predicted and measured 24-hour PER (Spearman correlation coefficient, ρ = 0.78), although the predicted PER underestimated the measured PER (Passing-Bablok regression, y = 1.54x-20.97 mg/24 hr). Importantly, a strong correlation (ρ = 0.93) and similar distribution (p=0.17) were found between the predicted and measured PER in Cohort B, with a much-reduced proportional bias (y = 1.06x+62.96 mg/24 hr). Furthermore, comparison of the difference between the predicted and measured PER between the two cohorts demonstrated the same prediction accuracy (p = 0.65), with a median difference (interquartile range) of 79 mg/24 hr (256) and 109 mg/24 hr (480) for Cohort A and B, respectively. Finally, a strong correlation (ρ = 0.85), similar distribution (p = 0.23), and little bias (y = 0.96x+28.14 mg/24 hr) existed between the predicted and measured PER for all patients with overt glucosuria (urine glucose ≥1000 mg/dL, n = 348). In summary, these data suggest that the established formula for predicted PER on RUS is equally valid for patients on or off SGLT2i, and that this result is a useful clinical estimating tool.

Background. Living kidney donation (KD) evaluation particularly focuses on glomerular filtration rate (GFR). Assessing GFR in living kidney donors can be done by estimation (eGFR) or measurement (mGFR). This study aims to evaluate the impact of eGFR equations, focusing on the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2021 equation for donor eligibility screening and the reclassification of donors excluded by eGFR criteria to mGFR assessments. Methods. Retrospective, single-center observational study of 2512 kidney donors evaluated between 2011 and 2023, at the Mayo Clinic. We performed analyses and comparisons of 4 eGFR formulae and 2 mGFR methods in terms of performance, eligibility criteria according to Kidney Disease: Improving Global Outcomes guidelines/age-adjusted criteria, eligibility reclassification, and subgroup analyses. Results. The CKD-EPI 2021 resulted in a higher percentage of patients being eligible for KD (81.4%) and achieved the highest P10 (32%–34%) and P30 (87%–88%) across all mGFR methods. When patients were deemed eligible for donation by any eGFR formula, 95% retained this status on reassessment with mGFR. Conversely, when an eGFR formula classified a patient as ineligible, this was revised to be eligible in about 90% of cases on reassessment with mGFR, with a higher reclassification rate observed when the IoCl was used instead of CrCl. Conclusions. The CKD-EPI 2021 performs best for screening potential KD. If a KD is deemed ineligible by CKD-EPI 2021, there is a high likelihood that they will be reclassified as eligible when assessed with mGFR. This study strongly supports using mGFR in donor evaluations, especially when the eGFR does not meet the criteria to ensure equity of access to being a living donor.

BACKGROUND: The performance of estimated glomerular filtration rate (eGFR) among patients with heart failure (HF) may be worse than in the general population due to a higher prevalence of confounding factors affecting creatinine and cystatin C. Studies in this area are scarce and not stratified by type of HF. We evaluated the performance of current creatinine and cystatin C equations (eGFRcr, eGFRcys, and eGFRcrcys) compared with measured GFR (mGFR) among patients with HF stratified by ejection fraction. METHODS: We pulled data on Mayo Clinic patients with an mGFR performed for clinical indications from 2011 to 2023, with serum creatinine and cystatin C measured within 7 days and an echocardiogram performed up to 1 year before the mGFR date. HF was identified by the presence of International Classification of Diseases codes within 1 year before the mGFR and subgrouped into ejection fraction (EF) ≥50% (HFEF≥50%, n=182) or <50% (HFEF<50%, n=115) and compared with no-HF controls (n=1871). CKD-EPI (and EKFC) eGFRcr, eGFRcys, and eGFRcrcys equations were calculated and compared for bias (mGFR minus eGFR) and accuracy (1-P30, proportion of people with ≥30% difference between eGFR and mGFR). CIs were generated by bootstrapping. RESULTS: The HF groups were characterized by older age, higher proportion of males, more diabetes, higher creatinine, and higher cystatin C than controls. In terms of bias, eGFRcr overestimated mGFR to a greater extent in both HF groups compared with controls, whereas eGFRcys and eGFRcrcys showed similar bias in both HF groups and controls. In the HF groups, cystatin C-based equations were more accurate than eGFRcr, particularly within HFEF<50% (1-P30 of 28% and 34% for CKD-EPI eGFRcys and eGFRcrcys, respectively, versus 60% for eGFRcr), whereas eGFRcrcys was more accurate in controls. The CKD-EPI and EKFC equations were overall convergent, showing similar results. CONCLUSIONS: Among patients with HF, eGFRcr demonstrates inferior performance (more bias and less accuracy) compared with cystatin C-based eGFRs, with this effect being more pronounced in those with HFEF<50%.

AbstractPancreas transplantation alone (PTA) is a β cell replacement option for selected patients with type 1 diabetes mellitus; concerns have been raised regarding deterioration in kidney function (KF) after PTA. This retrospective multicenter study assessed actual impact of transplantation and immunosuppression on KF in PTA recipients at three Transplant Centers. The primary composite endpoint 10 years after PTA was >50% eGFR decline, eGFR < 30 mL/min/1.73 m2, and/or receiving a kidney transplant (KT). Overall, 822 PTA recipients met eligibility. Median baseline and 10‐year eGFR (mL/min/1.73 m2) were 76.3 (58.1–100.8) and 51.3 (35.3–65.9), respectively. Primary composite endpoint occurred in 98 patients (53.5%) with 45 experiencing a >50% decrease in eGFR by 10 years post‐transplant, 38 eGFR < 30 mL/min/1.73 m2 and 49 requiring KT. KF declined most significantly within 6 months post‐PTA, more often in females and patients with better preserved GFR up to 5 years with 11.6% kidney failure at 10 years. Patient survival and death‐censored graft survival were both 68% at 10 years with overall graft thrombosis rate 8%. KF declined initially after PTA but stabilized with further slow progression. In conclusion, prospective intervention studies are needed to test renal sparing interventions while gathering more granular data.

Abstract Objective To compare the performance of a newly developed race-free kidney recipient specific glomerular filtration rate (GFR) equation with the three current main equations for measuring GFR in kidney transplant recipients. Design Development and validation study Setting 17 cohorts in Europe, the United States, and Australia (14 transplant centres, three clinical trials). Participants 15 489 adults (3622 in development cohort (Necker, Saint Louis, and Toulouse hospitals, France), 11 867 in multiple external validation cohorts) who received kidney transplants between 1 January 2000 and 1 January 2021. Main outcome measure The main outcome measure was GFR, measured according to local practice. Performance of the GFR equations was assessed using P 30 (proportion of estimated GFR (eGFR) within 30% of measured GFR (mGFR)) and correct classification (agreement between eGFR and mGFR according to GFR stages). The race-free equation, based on creatinine level, age, and sex, was developed using additive and multiplicative linear regressions, and its performance was compared with the three current main GFR equations: Modification of Diet in Renal Disease (MDRD) equation, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) 2009 equation, and race-free CKD-EPI 2021 equation. Results The study included 15 489 participants, with 50 464 mGFR and eGFR values. The mean GFR was 53.18 mL/min/1.73m 2 (SD 17.23) in the development cohort and 55.90 mL/min/1.73m 2 (19.69) in the external validation cohorts. Among the current GFR equations, the race-free CKD-EPI 2021 equation showed the lowest performance compared with the MDRD and CKD-EPI 2009 equations. When race was included in the kidney recipient specific GFR equation, performance did not increase. The race-free kidney recipient specific GFR equation showed significantly improved performance compared with the race-free CKD-EPI 2021 equation and performed well in the external validation cohorts (P 30 ranging from 73.0% to 91.3%). The race-free kidney recipient specific GFR equation performed well in several subpopulations of kidney transplant recipients stratified by race (P 30 73.0-91.3%), sex (72.7-91.4%), age (70.3-92.0%), body mass index (64.5-100%), donor type (58.5-92.9%), donor age (68.3-94.3%), treatment (78.5-85.2%), creatinine level (72.8-91.3%), GFR measurement method (73.0-91.3%), and timing of GFR measurement post-transplant (72.9-95.5%). An online application was developed that estimates GFR based on recipient’s creatinine level, age, and sex ( https://transplant-prediction-system.shinyapps.io/eGFR_equation_KTX/ ). Conclusion A new race-free kidney recipient specific GFR equation was developed and validated using multiple, large, international cohorts of kidney transplant recipients. The equation showed high accuracy and outperformed the race-free CKD-EPI 2021 equation that was developed in individuals with native kidneys. Trial registration ClinicalTrials.gov NCT05229939 .

Abstract Background The National Kidney Foundation recently endorsed the refit Chronic Kidney Disease Collaboration (CKD-EPI) equation for estimated glomerular filtration rate (eGFR) using creatinine, age and sex [2021 eGFRCr(AS)] without a coefficient for race. We evaluated the impact of adopting the 2021 eGFRCr(AS) equation or a variation of the 2009 CKD-EPI eGFR equation without race [2009 CKD-EPI eGFRCr(ASR-NB)] compared to the original CKD-EPI eGFR [2009 eGFRCr(ASR)]. Methods The studied population included patients with a clinically ordered iothalamate clearance (n = 33 889). Bias was assessed as the difference between measured and estimated GFR, P30 was defined as the percentage of estimates within 30% of measured GFR, and concordance was determined according to relevant clinical thresholds. Results Among Black patients, the median bias for 2009 eGFRCr(ASR), 2009 eGFRCr(ASR-NB), and 2021 eGFRCr(AS) was −1.32 mL min−1 (1.73 m2)−1 (95CI −2.46 to −0.26), −8.81 mL min−1 (1.73 m2)−1 (95CI −9.93 to −7.58), and −6.08 mL min−1 (1.73 m2)−1 (95CI −7.18 to −4.92), respectively. The median bias among non-Black patients was −0.15 m min−1 (1.73 m2)−1 (95CI −0.84 to −0.08) for 2021 eGFRcr(AS) compared to −3.09 mL min−1 (1.73 m2)−1 (95CI −3.17 to −3.03) for the 2009 eGFRCr(ASR). P30 and concordance were not significantly different in either racial group. The net reclassification improvement at a measured GFR &lt;20 mL min−1 (1.73 m2)−1 was 6.4% (95CI 0.36 to 12.4) for Black patients and −5.1% (95CI −6.0 to −4.1) for non-Black patients using the 2021 eGFRCr(AS) equation. Conclusions Overall, the change in reported eGFR was minimal. However, these changes led to significant reclassification improvements at lower eGFR, which will indirectly improve equitable access to CKD resources.

Abstract Abstract 2859 Background: PTLD is the most common malignancy, other than melanomatous skin cancer complicating solid organ transplantation and has been one of the most commonly observed fatal consequences. The histologies are diverse and include B-cell, T-cell and Hodgkin lymphomas. Rituximab has affected the outcome in CD20+ patients with PTLD. This single institution study sought to identity the outcomes in patients of all histologies and presentations managed in the post-rituximab era. Methods: Patients with solid organ transplantation who were diagnosed with PTLD at Mayo Clinic (Rochester, MN) between December 1970 and October 2009 were identified through the Mayo Clinic Lymphoma Data Base. The rituximab era was defined as patients diagnosed after December 26, 2000, the date of diagnosis for the first patient treated with rituximab in our series. Cox proportional hazards models were used to assess the association of clinical factors and overall survival (OS). Results: 143 patients diagnosed with PTLD between December 1970 and October 2009 were identified. The median age at the time of diagnosis of PTLD was 50 years (range 15–84) with 41 patients (29%) over the age of 60. 93 were male (65%). At a median follow-up of 84 months (range 1–295), 95 patients (65%) have died. The types of organ transplant included renal (39%), liver (31%), cardiac (11%), lung (6%), renal/pancreas (6%), pancreas (4%), and multiorgan (4%). 83% of patients presented with extranodal disease. 28% had involvement of the engrafted organ. 76% of the patients developed PTLD that was EBV+ by in situ hybridization. 62% were stage 3–4. The IPI was intermediate-high in 39% of patients. Initial approaches to management included reduction in immunosuppression (45%), chemotherapy (12%), reduction in immunosuppression with rituximab (12%), rituximab (8%), and radiation therapy (6%). The overall response to therapeutic approaches was 46% in the pre-rituximab era and 56% in the post-rituximab era (chi-squared p=0.25). Patients treated with rituximab had an improved overall survival (HR = 1.66, 95% CI: 0.99–2.79). Patients treated in the rituximab era had improved 1 year survival (76%) compared to patients in the pre-rituximab era (59%) (chi-squared p=0.03). However, the survival advantage in the rituximab era was not maintained in longer follow-up. The median overall survival in the pre-rituximab era was 31 months compared to 56 months in the post-rituximab era (logrank p=0.63). Conclusion: The overall response rates and overall survival are improved with rituximab treatment in CD20+ PTLD, however, the natural history of all PTLD has not improved significantly in the post-rituximab era. New approaches are needed for the prevention and management of all the histologies of PTLD. Disclosures: No relevant conflicts of interest to declare.

The role of nitric oxide (NO) in the regulation of the intrarenal microcirculation in streptozotocin (STZ)-induced diabetes mellitus in rats is not clear. We examined renal cortical and papillary hemodynamics in STZ rats and determined the effects of systemic inhibition and stimulation of NO synthesis. Renal blood flow in cortical (QCC), and inner medullary ascending (QAV) and descending (QDV) vasa recta capillaries was measured by fluorescence videomicroscopy in STZ Munich-Wistar rats and nondiabetic control rats. Ten days after STZ injection (80 mg/kg ip), basal QCCand QDVwere significantly greater in STZ rats ( n = 16) compared with control rats ( n = 15). Infusion of NG-monomethyl-l-arginine (l-NMMA, 15 mg/kg bolus, 500 μg ⋅ min−1⋅ kg−1iv) decreased QCC(−41%), QAV(−38%), and QDV(−37%) in control rats ( n = 6) and to a significantly greater magnitude than in STZ rats ( n = 7), QCC(−14%), QAV(−20%), and QDV(−25%). Coinfusion ofl-arginine (l-Arg, 1 mg ⋅ kg−1⋅ min−1iv) with l-NMMA increased QCCto a significantly greater extent ( P < 0.01) in control rats compared with STZ rats. In subsequent studies, infusion ofl-Arg alone increased QCC(+50%), QAV(+16%), and QDV(+11%) in control rats ( n = 5) but had no effect in STZ rats ( n = 5). These results show that the response of renal cortical and papillary capillary blood flow to both inhibition and stimulation of NO synthesis is attenuated in the early onset of STZ-diabetes mellitus rats compared with control rats.

Increases in renal interstitial hydrostatic pressure (RIHP) increase urinary sodium excretion (UNaV). Experimentally increasing RIHP by direct renal interstitial volume expansion (DRIVE) has been shown to decrease proximal tubule sodium reabsorption. The purpose of the present study was to investigate whether the renin-angiotensin system modulates the natriuretic response to DRIVE. Unilateral nephrectomy and implantation of two polyethylene matrices were performed 3 wk before the acute experiment. Fractional sodium excretion (FENa), RIHP, and glomerular filtration rate (GFR) were measured before and after DRIVE in control rats (n = 9) and in rats receiving the angiotensin II (ANG II) receptor antagonist, losartan potassium (10 mg/kg i.v.; n = 10). DRIVE was achieved by infusing 100 microliters of 2.5% albumin solution directly into the renal interstitium. GFR remained unchanged by DRIVE in both groups. In control animals, DRIVE significantly increased both RIHP (delta 3.8 +/- 0.5 mmHg) and FENa (delta 0.92 +/- 0.19%). In the losartan-treated group, RIHP (delta 2.8 +/- 0.4 mmHg) and FENa (delta 1.93 +/- 0.41%) also significantly increased. The natriuretic response to DRIVE was significantly enhanced during ANG II receptor blockade compared with control animals (delta UNaV/delta RIHP = 2.01 +/- 0.67 vs. 0.44 +/- 0.17 mu eq.min-1 x mmHg-1, respectively; P < 0.05). These results suggest that the blockade of angiotensin enhances the natriuretic response to increased RIHP during DRIVE.