From the Guidelines
Finding 1+ protein in urine without an elevated albumin/creatinine ratio suggests the presence of non-albumin proteins in the urine, which may indicate tubular proteinuria rather than glomerular proteinuria, and warrants further investigation. This situation is not necessarily an immediate cause for alarm, but it does require a thorough evaluation to determine the underlying cause of the proteinuria. According to the National Kidney Foundation practice guidelines for chronic kidney disease 1, the presence of proteinuria is a marker of kidney damage, and the type of proteinuria can indicate the underlying pathology.
The discrepancy between the dipstick test and the albumin/creatinine ratio occurs because dipstick tests detect all proteins, including immunoglobulins and Bence Jones proteins, while the albumin/creatinine ratio specifically measures albumin 1. This distinction is important because different types of proteinuria point to different underlying pathologies - glomerular disease typically shows albumin predominance, while tubular dysfunction or plasma cell disorders may show other proteins without significant albuminuria.
I recommend repeating the urinalysis to confirm the finding and ordering additional tests, including a comprehensive metabolic panel, complete blood count, and possibly a 24-hour urine collection to quantify protein excretion more accurately 1. Specific causes to consider include tubular dysfunction, overflow proteinuria from conditions like multiple myeloma, or transient proteinuria due to fever, exercise, or dehydration. While waiting for follow-up testing, it is essential to maintain good hydration and avoid excessive protein intake or strenuous exercise before testing.
Some key points to consider in the evaluation of proteinuria include:
- The use of untimed urine samples to detect and monitor proteinuria, as recommended by the National Kidney Foundation practice guidelines 1
- The importance of confirming proteinuria with a quantitative test, such as the albumin/creatinine ratio, to determine the severity of proteinuria 1
- The need to consider the type of proteinuria, including albuminuria and non-albumin proteinuria, to determine the underlying pathology 1
- The importance of evaluating patients with proteinuria for underlying kidney disease and other conditions that may be contributing to the proteinuria.
From the Research
Proteinuria Assessment
- Proteinuria is a strong predictor of adverse cardiovascular and kidney events, and an accurate assessment of proteinuria is important for the evaluation and management of CKD 2
- Total urinary protein can be assessed using dipstick, precipitation, and electrophoresis methods, while urinary albumin can be assessed using an albumin-specific dipstick, immunochemical techniques, and size-exclusion high-performance liquid chromatography 2
1+ Protein in Urine without Elevation in Albumin/Creatinine Ratio
- There is no direct evidence in the provided studies to explain the presence of 1+ protein in urine without an elevation in albumin/creatinine ratio
- However, it is known that proteinuria can be caused by various factors, including kidney disease, diabetes, and hypertension, and that the assessment of proteinuria is important for the evaluation and management of these conditions 2, 3, 4, 5, 6
Treatment of Proteinuria
- Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are commonly used to treat proteinuria in patients with diabetic kidney disease 3, 4, 5, 6
- Non-dihydropyridine calcium channel blockers (non-DHP CCBs) may also be effective in reducing proteinuria in patients with diabetic kidney disease 3
- The use of ACEIs or ARBs may reduce the risk of end-stage renal disease and slow the progression of nephropathy, but they do not appear to decrease all-cause or cardiovascular mortality in people with Type 2 diabetes and proteinuria 6