Urine Protein

Aka: Urine Protein, Urine Albumin, Urine Dipstick Protein

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II. Interpretation: Normal

  1. Dipstick with trace Protein or less
  2. Protein 1+ or greater is considered abnormal, suggesting glomerular injury

III. Technique

  1. First morning void collected
    1. Orthostatic Proteinuria (benign, common cause in male teens) may be seen with later samples in the day
  2. Detection Method
    1. Initial: Dipstick Urine Protein
      1. High Test Sensitivity and Test Specificity (>99%) for albumin, but not for other Proteins
    2. Confirmation
      1. Urine Protein to Creatinine Ratio
      2. Sulfosalicylic Acid Test (older test)
  3. Dipstick turns from yellow to green for Protein present (Tetrabromophenol blue colorimetric method)
    1. Negative: <10 mg/dl
    2. Trace: 10-20 mg/dl
    3. Protein 1+: 30 mg/dl (abnormal)
    4. Protein 2+: 100 mg/dl
    5. Protein 3+: 300 mg/dl
    6. Protein 4+: 1000 mg/dl

IV. Causes: Increased Urine Protein

  1. See Proteinuria in Adults
  2. See Proteinuria in Children

V. Causes: False Positive Urine Protein

  1. Alkaline urine (Urine pH >8)
  2. Increased Urine Specific Gravity (concentrated, Urine Specific Gravity >1.030)
  3. Dipstick immersed too long in urine (or placed directly in urine stream)
  4. Non-albumin Proteins
  5. Medications
    1. Penicillin
    2. Sulfonamide
    3. Tolbutamide
    4. Phenazopyridine (Pyridium)
    5. Chlorhexidine contamination (Hibiclens, Peridex)
    6. Iodinated radiocontrast in urine
    7. Benzalkonium
    8. Quaternary Ammonium Compounds (QAC, Quaternary Amines) found in disinfectants (Quats)
  6. Body fluid contamination
    1. Gross Hematuria present
    2. Bacteriuria
    3. Pus
    4. Semen
    5. Vaginal secretions

VI. Causes: False Negative Urine Protein

  1. Albumin is not the primary Protein
    1. Light chain Protein (detected by Sulfosalicylic acid)
  2. Dilute urine (Urine Specific Gravity <1.010)
  3. Urine Protein concentration <10 mg per deciliter
  4. Urine pH decreased (pH <4.5)

VII. References

  1. Hitzeman (2022) Am Fam Physician 106(1): 27-35 [PubMed]
  2. Leung (2017) Am Fam Physician 95(4): 248-54 [PubMed]
  3. Simerville (2005) Am Fam Physician 71(6): 1153-62 [PubMed]

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