Proteinuria (positive dipstick, raised urine protein:creatinine or albumin:creatinine ratio)

• Acute kidney injury or rapid deterioration with extrarenal signs: nephrologist the same day.
• Nephrotic syndrome, oedema, haematuria, refractory hypertension: nephrologist promptly.

If the tests have not already been done

• Serum creatinine with eGFR
• Urine protein:creatinine ratio (spot sample)
• Serum albuminif neededOedema or heavy proteinuria: nephrotic syndrome combines proteinuria > 3 g/24 h and serum albumin < 30 g/L ^[2].

First morning urine, away from fever, exertion, menstruation, infection

• Urine protein:creatinine ratio (spot sample)
• Urine albumin:creatinine ratio on the same sampleif neededTo know whether the proteinuria is made of albumin (glomerular) or other proteins (tubular, light chains), which albumin dipsticks can miss ^[1,2].
• Urine microscopy and culture
• Serum creatinine with eGFR

Laboratory tests

• Serum creatinine with eGFR
• Urine protein:creatinine ratio (spot sample)
• Urine albumin:creatinine ratio on the same sampleif neededTo classify albuminuria (A1 to A3) and know whether the proteinuria is made of albumin ^[1,2].
• Urine microscopy and culture (red cells, white cells, casts)
• Serum protein electrophoresis
• Serum albuminif neededOedema or proteinuria > 3 g/24 h: look for nephrotic syndrome (serum albumin < 30 g/L) ^[2].
• Urine protein electrophoresis and immunofixationif neededProteinuria made mostly of proteins other than albumin, or abnormal serum electrophoresis: look for a monoclonal light chain ^[1]; Bence Jones only if proteinuria > 50 mg/L ^[3].
• Complement C3, C4, antinuclear antibodies, ANCAif neededSigns of systemic disease (rash, arthralgia, purpura, lung involvement): immunological tests for aetiology ^[2].

In 3 months

• Serum creatinine, ACR or urine protein:creatinine ratio (chronicity)

• Oedema, macroscopic haematuria, severe hypertension, extrarenal signs or renal failure: prompt opinion of a paediatric nephrologist.

First morning urine (on waking), away from fever, exertion or infection

• Urine protein:creatinine ratio (spot sample)
• Urine albumin:creatinine ratio on the same sample
• Urine microscopy and culture (if leucocytes, nitrites or blood on the dipstick)if neededDipstick suggesting a urinary tract infection: infection causes transient proteinuria ^[2]; repeat the test later.
• Serum creatinineif neededProteinuria confirmed on morning urine, oedema or hypertension: organic renal failure is a warning sign that requires the opinion of a paediatric nephrologist ^[7].
• Serum albuminif neededOedema or UPCR > 200 mg/mmol: nephrotic syndrome in children combines UPCR > 200 mg/mmol and serum albumin < 30 g/L ^[7].