#2018 Characteristics of patients with complement 3 glomerulopathy (C3G): a retrospective linked electronic medical record (EMR) and claims analysis
Authors: Ndife Briana , Aldworth Carolina , Murphy Kathleen , Thakkar Karishma , Olson Stephen , Nagelhout Elizabeth , Boyd Marley , Leiras Claudia , Gor Deval 
Published: May 2024

Abstract

Background and Aims
C3G is characterised by C3 deposition in the glomeruli, caused by dysregulation of the alternative complement pathway. Contemporary datasets on the clinical burden of patients with C3G in the United States (US) are limited. The aim of this analysis was to describe the demographics and clinical characteristics of patients diagnosed with C3G in the US.

Methods
This was a retrospective cohort analysis of patients with C3G included in the US HealthVerity database with an EMR and linked pharmacy and medical claims data, who were diagnosed between January 1, 2017 and March 31, 2022 and aged ≥12 years at diagnosis. The index date was the date of the first C3G diagnosis, identified by International Classification of Diseases 10th Revision Clinical Modification (ICD-10-CM) and Systematized Nomenclature of Medicine (SNOMED) diagnosis codes. Included patients had database records for ≥12 months before the index date (the baseline period). Patients aged ≥50 years with monoclonal gammopathy of unknown significance (MGUS) were excluded. Patient demographic and clinical characteristic data for the overall population, and stratified by transplant status, were summarised with descriptive statistics.

Results
Overall, 2021 patients had ≥1 diagnosis of C3G in the US HealthVerity database during the identification period. Of these, 1060 patients did not meet the criteria for the analysis, including 44 patients (2.2%) who were excluded due to the presence of a diagnostic code for MGUS at ≥50 years of age. The final cohort included 961 patients, of whom 62.4% were female. At the index date, mean (standard deviation [SD]) age was 44.4 (19.6) years (Table 1); 80 patients (8.3%) were aged &lt;18 years, 881 (91.7%) were aged ≥18 years, and 156 (16.2%) were aged ≥65 years. Median (lower quartile [Q1], upper quartile [Q3]) database history was 41.7 (25.9, 66.8) months, and mean (SD) follow-up time from the index date was 22.7 months (16.4). Comorbidities recorded during the baseline period included hypertension (57.4%), type II diabetes (25.1%), and congestive heart failure (12.9%). Among patients who were aged ≥65 years vs &lt;65 years at the index date, the proportion of patients with hypertension (93.6% vs 50.4%), type II diabetes (52.6% vs 19.8%), and congestive heart failure (32.1% vs 9.2%) were numerically higher. Of 461 patients (48.0%) with a known chronic kidney disease stage, 282 (61.2%) had stage 3–5 chronic kidney disease during the baseline period. Baseline estimated glomerular filtration rate (eGFR) data were available for 205 patients (21.3%); overall, median (Q1, Q3) eGFR values were 82.0 (48.0, 107.0) mL/min/1.73 m2, and 56.6% of patients had an eGFR value of &lt;90 mL/min/1.73 m2. Among 78 patients (8.1%) with proteinuria data during the baseline period, median (Q1, Q3) proteinuria levels were 1.4 (0.3, 3.3) g/g, and 44 patients (56.4%) had a proteinuria level ≥1.0 g/g. Extrarenal manifestations including ocular haemorrhage/retinal occlusion, pulmonary haemorrhage, ocular drusen, and acquired partial lipodystrophy were recorded in 1.7%, 0.9%, 0.5%, and 0.1% of patients, respectively. Overall, 19 patients (2.0%) had previously undergone a kidney transplant; the proportion who had hypertension, type II diabetes, or congestive heart failure during the baseline period was 89.5%, 31.6%, and 10.5%, respectively. Baseline eGFR data were available for 4 patients (21.1%) who had previously received a kidney transplant (Table 1).

Conclusions
This contemporary assessment of patients with C3G, using real-world EMR and administrative claims data from a national US cohort, showed that comorbidities around the time of C3G diagnosis were common. Among patients with available eGFR data, the majority exhibited reduced kidney function during the baseline period.