From the Guidelines
Nephrotic syndrome in children is diagnosed when a patient presents with the triad of heavy proteinuria, hypoalbuminemia, and edema, with proteinuria exceeding 40 mg/m²/hour or a urine protein-to-creatinine ratio greater than 2.0 mg/mg (or 200 mg/mmol) in a spot urine sample, and serum albumin less than 2.5 g/dL, as defined by the most recent guideline 1. The diagnostic criteria for nephrotic syndrome in pediatric patients include:
- Heavy proteinuria, defined as exceeding 40 mg/m²/hour or a urine protein-to-creatinine ratio greater than 2.0 mg/mg (or 200 mg/mmol) in a spot urine sample
- Hypoalbuminemia, defined as serum albumin less than 2.5 g/dL
- Edema, typically generalized and may be observed in dependent areas like the periorbital region, lower extremities, or genitalia
- Hyperlipidemia (elevated cholesterol and triglycerides) is often present but not required for diagnosis A kidney biopsy is not routinely needed for initial diagnosis in children aged 1-10 years with typical presentation, as most (approximately 80%) will have minimal change disease, as stated in the guideline 1. However, biopsy should be considered in children with atypical features such as persistent hematuria, hypertension, low complement levels, or steroid resistance. The following tests should be obtained at diagnosis:
- Urinalysis
- Complete blood count
- Comprehensive metabolic panel
- Lipid profile These diagnostic criteria help clinicians identify nephrotic syndrome promptly, allowing for timely initiation of appropriate therapy, typically starting with oral prednisone at 60 mg/m²/day (maximum 60 mg/day) for 4-6 weeks, followed by alternate-day therapy, as recommended by the guideline 1. It is worth noting that the definition of nephrotic syndrome has been consistent across guidelines, with the most recent commentary suggesting that serum albumin of ≤2.5 g/dL should continue to be used as a component of the definition of nephrotic syndrome for children, in the absence of evidence to support a change to a higher cutoff 1.
From the Research
Diagnostic Criteria for Nephrotic Syndrome in Pediatric Patients
The diagnostic criteria for nephrotic syndrome in pediatric patients include:
- Nephrotic-range proteinuria, defined as ≥40 mg/m2/hour or urine protein/creatinine ratio ≥200 mg/mL or 3+ protein on urine dipstick 2
- Hypoalbuminemia, defined as <25 g/L 2, 3
- Edema, which can be periorbital or dependent pitting oedema 4
- Hyperlipidemia, which is often associated with nephrotic syndrome 5, 4
Methods for Detecting Proteinuria
Several methods can be used to detect proteinuria in pediatric patients with nephrotic syndrome, including:
- 24-hour urinary protein excretion, which is the accepted method for quantifying proteinuria 3, 6
- Spot urinary protein/creatinine ratio, which can be used as a reliable diagnostic tool to quantify proteinuria 3, 6
- Urine protein analysis using the sulphosalicylic acid method and creatinine estimation by a modified Jaffe's method 3
Correlation between Spot Protein/Creatinine Ratio and 24-Hour Proteinuria
Studies have shown a statistically significant correlation between spot protein/creatinine ratio and 24-hour proteinuria in pediatric patients with nephrotic syndrome, with a Pearson correlation coefficient of 0.833 (P < 0.01) 3 and 0.805 6. This suggests that spot urinary protein/creatinine ratio can be used as a reliable test for detecting proteinuria in pediatric patients with nephrotic syndrome.