Comparison of Patients with Hospital-Recorded Nephrotic Syndrome and Patients with Nephrotic Proteinuria and Hypoalbuminemia: A Nationwide Study in Denmark

Abstract

Background: Registry-based studies of nephrotic syndrome (NS) may only include a subset of patients with biochemical features of NS. To address this, we compared patients with laboratory-recorded nephrotic proteinuria and hypoalbuminemia to patients with hospital-recorded NS. Methods: We identified adult patients with first-time hospital-recorded NS (inpatients, outpatients or emergency room visitors) in the Danish National Patient Registry and compared them to adults with first-time recorded nephrotic proteinuria and hypoalbuminemia in Danish laboratory databases during 2004-2018, defining date of admission or laboratory findings as index date. We characterised these cohorts by demographics, comorbidity, medication use, and laboratory and histopathological findings. Results: We identified 1,139 patients with hospital-recorded NS and 5,268 patients with nephrotic proteinuria and hypoalbuminemia of which 760 patients were identified with both. Within one year of the first recorded nephrotic proteinuria and hypoalbuminemia, 18% had recorded hospital diagnoses indicating the presence of NS, while 87% had diagnoses reflecting any kind of nephropathy. Among patients identified with nephrotic proteinuria and hypoalbuminemia, most recent eGFR was substantially lower (median of 35 vs. 61 ml/min/1.73 m2), fewer underwent kidney biopsies around index date (34% vs. 61%), and prevalence of thromboembolic disease (25% vs 17%) and diabetes (39% vs. 18%) was higher when compared to patients with hospital-recorded NS. Conclusions: Patients with nephrotic proteinuria and hypoalbuminemia are five-fold more common than patients with hospital-recorded NS, and they reveal a lower eGFR and more comorbidity. Selective and incomplete recording of NS may be an important issue when designing and interpreting studies of risks and prognosis of NS.

Risk of Arterial Thromboembolism, Venous Thromboembolism, and Bleeding in Patients with Nephrotic Syndrome: A Population-Based Cohort Study

“…First, we relied on recorded diagnoses to identify first-time NS, potentially overlooking NS patients without a diagnosis code specific to NS. 46 Furthermore, less severe events of VTE may have been diagnosed and recorded in NS patients than in the general population, which would lead to overestimating the association between NS and VTE. However, guidelines do not recommend screening asymptomatic NS patients for VTE by radiological examination.…”

Serum albumin and white matter hyperintensities

“…Albumin in urine, typically quantified as the urine albumin to creatinine ratio (uACR), is present as a continuous variable ranging from very low in healthy individuals to high fractions (e.g., > 30mg/g microalbuminuria, > 300mg/g macroalbuminuria) in nephrotic syndrome [ 1 , 2 ]. Albuminuria is independently associated with increased incidence of cardiovascular events after consideration of traditional risk factors such as high body mass index (BMI), nicotine use, diabetes, and hypertension [ 3 – 7 ].…”

From Dropsy to Chart Biopsy: Opportunities and Pitfalls of Electronic Health Records

“…In this work, Vestergaard et al compared patients with biochemical features of NS to patients with hospital-recorded NS within the Danish National Patient Registry in Denmark from 2004–2018 (3). The authors hypothesized that more patients would be identified by laboratory criteria than coded diagnoses.…”