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IntroductionInformation on the economic burden of focal segmental glomerulosclerosis (FSGS) is sparse. This study characterized health care resource utilization (HCRU) and costs in patients with FSGS, and evaluated the impact of nephrotic range proteinuria on these outcomes.MethodsThis retrospective, observational cohort study used administrative claims data from the Optum Clinformatics Data Mart Database from October 2015 to December 2019. Patients with FSGS (n = 844; first claim = index event) between April 2016 and December 2018 were matched on index date, age, sex, and race to non-FSGS controls (n = 1688). FSGS nephrotic range (urine protein/creatinine ratio >3000 mg/g or albumin/creatinine ratio >2000 mg/g) and non-nephrotic subpopulations were identified. Baseline comorbidities, 12-month post-index all-cause HCRU and costs (per patient per year [PPPY]), and immunosuppressant prescriptions were compared between matched cohorts and between FSGS subpopulations.ResultsComorbidity burden was higher in FSGS. Of 308 patients with available urine protein/creatinine ratio/albumin/creatinine ratio results, 36.4% were in nephrotic range. All-cause HCRU was higher in FSGS across resource categories (all P < 0.0001); 50.6% of FSGS and 23.3% of controls were prescribed glucocorticoids (P < 0.0001). Mean total medical costs were higher in FSGS ($59,753 vs. $8431 PPPY; P < 0.0001), driven by outpatient costs. Nephrotic range proteinuria was associated with higher all-cause inpatient, outpatient, and prescription costs versus nonnephrotic patients (all P < 0.0001), resulting in higher total costs ($70,481 vs. $36,099 PPPY; P < 0.0001).ConclusionsFSGS is associated with significant clinical and economic burdens; the presence of nephrotic range proteinuria increased the economic burden. New treatment modalities are needed to reduce proteinuria, help improve patient outcomes, and reduce HCRU and associated costs.

Abstract Background and Aims The burden of disease associated with FSGS has not been well characterized, especially with regard to health care resource utilization (HCRU) and related costs. The aim of this study was to evaluate all-cause HCRU and estimate associated costs in patients with FSGS compared with a matched non-FSGS cohort; a secondary aim was to evaluate the impact of nephrotic range proteinuria on these outcomes. Method Data were from the Optum Clinformatics® Data Mart Database. Patients with ≥ 1 claim (1st claim = index event) for FSGS between April 2016 and December 2018 were identified based on ICD-10-CM codes and matched 1:2 (FSGS:controls) on index date, age, sex, and race to non-FSGS controls; continuous enrollment 6 months pre- and 12 months post-index was required. FSGS nephrotic range (either UPCR >3000 mg/g or ACR >2000 mg/g) and non-nephrotic subpopulations were also identified. Quan-Charlson Comorbidity Index (CCI) and individual comorbidities at baseline, and 12-month post-index all-cause HCRU and associated costs (per patient per year [PPPY]) as well as medication prescriptions related to FSGS treatment were compared between the matched cohorts and between the FSGS subpopulations; t-tests were used for continuous variables and chi-square tests for categorical variables. Results 844 patients with FSGS were matched with 1688 non-FSGS controls; 57.4% male, 56.9% white, mean (SD) age 54.7 (18.4) years. Mean (SD) CCI was higher in the FSGS cohort relative to matched controls (2.72 [2.12] vs 0.55 [1.29]; P < .0001), with prevalence of most individual comorbidities higher in the FSGS cohort. Only 308 FSGS patients (36.5%) had UPCR or ACR tests with available results during the review period; 112 (36.4%) were in the nephrotic range and 196 were non- nephrotic (63.6%). The FSGS cohort was characterized by higher rates of all-cause HCRU across resource categories (all P < .0001) (Table 1); outpatient visits was the most frequently used category (99.1% vs 69.0%), followed by prescription medications. Among patients who used these resources, units of use were significantly higher in FSGS vs matched controls except for length of stay (Table 1). Readmission rates following 1st post-index hospitalization were higher in the FSGS cohort vs matched controls at 30 days (16.1% vs 6.0%; P < .05) and 365 days (39.1% vs 22.9%; P < .05). Glucocorticoids were the most frequently prescribed FSGS-related medication in both cohorts, with a higher rate in FSGS vs matched controls (50.6% vs 23.3%; P < .0001); other FSGS-related medications were infrequently prescribed (< 14%). Inpatient, outpatient, and prescription costs were higher in the FSGS cohort vs matched controls (all P < .0001) resulting in mean total annual medical costs of $59,753 vs $8,431 PPPY (P < .0001) that were driven by outpatient costs (Fig. 1A). Nephrotic range proteinuria was associated with higher all-cause inpatient, outpatient, and prescription costs vs non-nephrotic patients (all P < .0001; Fig. 1B), resulting in higher total costs ($70,481 vs $36,099 PPPY; P < .0001). A higher proportion of nephrotic range patients were prescribed FSGS-modifying medications (73.2% vs 54.1%; P = 0.001), with glucocorticoids the most frequent medication. However, 26.8% of nephrotic range patients were not prescribed any FSGS-related medications. Conclusion FSGS is associated with significant clinical and economic burdens with total annual medical costs > 7-fold higher than matched controls that were driven by outpatient costs. The presence of nephrotic range proteinuria substantially and significantly increased the economic burden. New treatment modalities leading to lower rates of proteinuria may help improve patient outcomes while reducing HCRU and their associated costs.

CKD is frequently diagnosed only after a significant progression. GFR is the most common indicator of kidney function but is limited in detecting early CKD cases and distinguishing glomerular, tubular, and global CKD. Aiming to provide a glomeruli specific biomarker assay, we developed a peptide immunoaffinity targeted mass spectrometry method for the quantitation of three podocyte specific proteins in human urine: nephrin, podocalyxin, and podocin. Proteins in urine were precipitated, stable isotope labeled peptide standards incorporated, and digested with trypsin. Target peptides were enriched using an online antibody column prior to LC-MS/MS. The performance metrics for nephrin, podocalyxin, and podocin were evaluated: The lower limits of quantitation were 3.8, 22.0, and 5.4 pM, respectively. The intraplate relative error (RE) was within ±10.6%, ± 10.4%, and ±16.1%, and coefficient of variation (CV) was ≤27.2%, ≤ 14.1%, and ≤20.7% accordingly. The interplate RE was within ±7.0%, ± 3.8%, and ±3.0%, and CV was ≤17.2%, ≤ 12.1%, and ≤20.0% for the three analytes. The urinary nephrin, podocalyxin, and podocin concentrations in 60 healthy volunteers and 20 disease samples was measured, thereby establishing the basal levels of these protein and enabling future evaluation of their roles as noninvasive biomarkers of glomerular injury in the clinic.