No, Sub-Nephrotic Range Proteinuria is NOT Nephritic Syndrome
Sub-nephrotic range proteinuria (150 mg/day to 3.5 g/24h) is neither nephrotic syndrome nor nephritic syndrome—these are distinct clinical entities defined by different criteria.
Clear Definitions of Each Syndrome
Nephrotic Syndrome Requires:
- Proteinuria ≥3.5 g/24 hours (or protein-to-creatinine ratio ≥3,500 mg/g) 1, 2
- Serum albumin <3.0 g/dL in adults 1, 2
- Edema 1, 3
- Often accompanied by hyperlipidemia and thrombotic risk 3, 4
Nephritic Syndrome is Characterized by:
- Hematuria (the hallmark feature) 4
- Proteinuria (typically sub-nephrotic range, though can vary) 4
- Hypertension 4
- Abnormal kidney function with active urinary sediment 4
- Generally carries a poorer prognosis than isolated proteinuria 4
Why the Confusion Exists
The terminology can be misleading because proteinuria exists on a spectrum, but the syndromes are defined by clinical presentation patterns, not just proteinuria amount:
- Sub-nephrotic proteinuria (300-3,500 mg/day) is simply a quantitative descriptor 5, 6
- Nephritic syndrome is a clinical syndrome defined by inflammatory glomerular injury with hematuria, not by proteinuria thresholds 4
- Nephrotic syndrome requires the complete triad—proteinuria alone is insufficient 1, 2
Clinical Significance of Sub-Nephrotic Proteinuria
Prognosis Depends on Progression:
- Patients with sustained sub-nephrotic proteinuria have excellent long-term outcomes with progression rates of only -0.93 ml/min/year 5
- However, approximately 60% of patients initially presenting with sub-nephrotic proteinuria will progress to nephrotic range, most within the first year 5
- Those who progress to nephrotic range have four times faster decline (-3.52 ml/min/year) 5
Diagnostic Considerations:
- Sub-nephrotic proteinuria warrants kidney biopsy evaluation, as 34.4% have primary glomerulopathies requiring specific treatment 6
- Within the sub-nephrotic range, each 100 mg/g increase in proteinuria increases risk of ESRD and death (HR 1.05,95% CI: 1.02-1.09) 6
- Sub-nephrotic proteinuria is a well-recognized cardiovascular risk factor independent of renal function 7
Common Pitfalls to Avoid
- Do not use "nephritic" and "nephrotic" interchangeably—they describe fundamentally different pathophysiologic processes 4
- Do not diagnose nephrotic syndrome based on proteinuria alone—albumin and edema are required 1, 2
- Do not assume sub-nephrotic proteinuria is benign—close monitoring is essential as progression risk is substantial 5, 6
- Always check for hematuria to distinguish nephritic from nephrotic presentations 4