In a 14‑year‑old with a random urine dipstick indicating proteinuria greater than 300 mg/dL, what is the appropriate next step in evaluation and management?

Evaluation of Proteinuria >300 mg/dL in a 14-Year-Old

Confirm the proteinuria with a first-morning urine protein-to-creatinine ratio (PCR) to exclude transient and orthostatic causes before pursuing any further workup. 1

Immediate Next Steps

Rule Out Transient Causes First

• Check for urinary tract infection with urinalysis and culture, as symptomatic UTIs cause transient proteinuria that resolves after antimicrobial treatment 1
• Verify the patient avoided vigorous exercise for 24 hours before the specimen, as physical activity causes temporary protein elevation in adolescents 1, 2
• In menstruating females, avoid collection during menses to prevent false-positive results from blood contamination 1

Obtain Quantitative Confirmation

• Order a first-morning void spot urine protein-to-creatinine ratio (PCR) rather than a 24-hour collection, as this is the preferred method in pediatric patients and eliminates the inaccuracy of timed collections in children 1, 2
• First-morning specimens are essential in adolescents to distinguish pathologic proteinuria from benign orthostatic (positional) proteinuria, which is common in school-age children and disappears when supine 1, 2
• Normal PCR values in children are <200 mg/g (0.2 mg/mg), and values ≥200 mg/g indicate pathologic proteinuria requiring further evaluation 1

Risk Stratification Based on PCR Results

If PCR <200 mg/g (Normal)

• No further workup is needed if the first-morning PCR is normal, as this confirms benign orthostatic or transient proteinuria 1, 3
• Orthostatic proteinuria has an excellent long-term prognosis and does not progress to kidney disease in adolescents 3

If PCR 200-1000 mg/g (Moderate Proteinuria)

• Confirm persistence by obtaining a second PCR within 3 months; two positive results out of three samples define persistent proteinuria 1
• Obtain baseline eGFR to assess kidney function and stage any chronic kidney disease 4
• Examine urine sediment for dysmorphic red blood cells, red cell casts, or white cell casts, which suggest glomerular disease 5, 1
• Check blood pressure at every visit, as hypertension with proteinuria indicates higher risk 1

If PCR ≥1000 mg/g (Significant Proteinuria)

• Immediate nephrology referral is warranted, as this level of proteinuria in an adolescent suggests glomerular disease requiring specialized evaluation 1
• Obtain comprehensive serologic testing including ANA, anti-dsDNA, complement levels (C3, C4), and ANCA if glomerulonephritis is suspected 4
• Consider lupus nephritis specifically in this age group, as childhood-onset SLE is associated with higher incidence and more severe nephritis than adult-onset disease 5

If PCR >3500 mg/g (Nephrotic-Range)

• Urgent nephrology referral and likely kidney biopsy are required to determine the underlying cause and guide immunosuppressive therapy 1, 4
• This represents high risk for progressive kidney disease and cardiovascular events 1

Common Pitfalls to Avoid

• Do not order a 24-hour urine collection in a 14-year-old, as these are cumbersome, frequently incomplete, and inaccurate in pediatric patients 1
• Do not assume a single dipstick is diagnostic—transient proteinuria from fever, exercise, or dehydration is extremely common in adolescents and requires confirmation 1, 2
• Do not delay the first-morning void collection, as random daytime specimens will miss orthostatic proteinuria and lead to unnecessary workups 1, 2
• Do not initiate treatment (such as ACE inhibitors) before confirming persistent proteinuria with repeat testing 1

Special Considerations in Adolescents

• Orthostatic proteinuria is the most common cause of isolated proteinuria in school-age children and adolescents, occurring in up to 2-4% of this population 2, 3, 6
• Persistent proteinuria in adolescents (defined as ≥80% of samples positive over 3 months) represents a heterogeneous group, with a significant proportion having serious glomerular pathology that can progress to renal disease 3
• The combination of proteinuria with hematuria carries a more severe prognosis and mandates nephrology referral regardless of the degree of proteinuria 2, 7