What initial investigations should I perform for a patient presenting with proteinuria?

Initial investigations for a patient presenting with proteinuria should include:

• Measurement of urine albumin:creatinine ratio (ACR) rather than protein:creatinine ratio (PCR) for initial detection, due to greater sensitivity for low levels of proteinuria.
• If the initial ACR is between 3 mg/mmol and 70 mg/mmol, confirm the result with a repeat early morning urine ACR sample; if the ACR is 70 mg/mmol or more, a repeat sample is not required.
• Assess estimated glomerular filtration rate (eGFR) using serum creatinine to evaluate kidney function.
• Use reagent strips to test for haematuria; if 1+ or higher, further evaluation is needed.
• If proteinuria is an incidental finding on reagent strips, offer testing for chronic kidney disease (CKD) using eGFR and ACR.

These investigations help confirm the presence and quantify the degree of proteinuria, assess kidney function, and identify any associated haematuria that may indicate underlying pathology.

Note: Reagent strips should not be used to identify proteinuria unless they specifically measure albumin at low concentrations and express results as ACR. Reagent strips are not recommended for proteinuria detection in children and young people.

References: NICE NG203