What is the classification and description of Urinalysis (UA) results, including the range and meaning of 1+ and 2+ designations?

From the Guidelines

UA classification is a semi-quantitative scale used to indicate concentration levels of substances in urine, with 1+ indicating a small amount, 2+ a moderate amount, 3+ a large amount, and 4+ a very large amount, as guided by the American Urological Association's best practice policy recommendations 1. The "+" system is used to report the presence and concentration of various substances in the urine, such as protein, blood, or glucose.

• The scale typically ranges from trace or 1+ to 4+, with each "+" indicating a higher concentration of the substance.
• For proteinuria, the scale is as follows:
  • 1+ indicates approximately 30 mg/dL
  • 2+ indicates approximately 100 mg/dL
  • 3+ indicates approximately 300 mg/dL
  • 4+ indicates greater than 1000 mg/dL
• According to the American Urological Association's best practice policy recommendations, proteinuria of 1+ or greater on dipstick urinalysis should prompt further evaluation, such as a 24-hour urine collection to quantitate the degree of proteinuria 1. The UA classification system is useful for quickly assessing the severity of conditions like proteinuria, hematuria, or glycosuria, and for monitoring trends over time.
• However, it is essential to note that the semi-quantitative nature of this scale means that quantitative tests may be needed for precise measurements in cases where exact concentrations are clinically important.
• The American Urological Association recommends that a total protein excretion of > 1,000 mg per 24 hours (1 g per day) should prompt a thorough evaluation or nephrology referral, and consideration should also be given to evaluating lower levels of proteinuria (> 500 mg per 24 hours [0.5 g per day]) if the protein excretion is increasing or persistent, or if there are other factors suggestive of renal parenchymal disease 1.

From the Research

UA Classification Description

• The UA classification description refers to the measurement of proteinuria, which is the presence of excess proteins in the urine.
• The range of proteinuria can vary, but it is typically measured in terms of grams per day or milligrams per millimole of creatinine.
• A 1+ or 2+ rating on a urine dipstick test indicates the presence of proteinuria, with 1+ being a trace amount and 2+ being a moderate amount 2.
• The severity of proteinuria can be classified as follows:
  • Microalbuminuria: 30-300 mg/24 hours or 30-300 mg/g creatinine
  • Macroalbuminuria: >300 mg/24 hours or >300 mg/g creatinine
• The measurement of proteinuria is important in the assessment of chronic kidney disease (CKD) and can be used to monitor the progression of the disease 3.

Proteinuria Measurement

• Proteinuria can be measured using a variety of methods, including urine dipstick tests, 24-hour urine collections, and spot urine samples.
• The total protein:creatinine ratio (TPCR) and albumin:creatinine ratio (ACR) are commonly used to measure proteinuria 3.
• TPCR is highly correlated with 24-hour urine protein, and a threshold of 100 mg/mmol has a higher sensitivity and lower specificity than an ACR of 70 mg/mmol for predicting 1 g/day of total proteinuria 3.

Clinical Significance

• Proteinuria is a significant predictor of mortality and morbidity in patients with CKD and heart failure 2.
• The presence of proteinuria is associated with a higher risk of cardiovascular events and progression of CKD 2.
• Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) have been shown to reduce proteinuria and slow the progression of CKD 4, 2.