Diagnostic Laboratory Section

TESTS FOR PROTEINS

Heller’s Nitric acid test

• Take 2 ml of urine in a tube
• Add 2 ml of Conc. HNO₃ along the sides of the tube slowly.
• An appearance of a white ring at the junction of the two liquids indicates the presence of proteins.

Biuret Test

• Take 2 ml of urine in a test tube
• Add 1 ml of 5% NaOH and 1-2 drops of 1% copper sulphate.
• Production of a violet color indicates the presence of bonds in proteins. Aminoacids will give a negative result.

Interpretation

Physiological proteinuria

• It is transient and believed to be due to a temporary increased glomerular permeability as a result of capillary congestion.
  • Excessive muscular exertion
  • Convulsion
  • Emotional stress
  • Ingestion of an excessive amount of protein

Pathological proteinuria

• Pre-renal: The protein originates from non-renal conditions and its loss in the urine is not due to primary renal disease.
  • Bence – Jone’s protein
  • Haemoglobinuria
  • Myoglobinuria
• Renal
  • Increased permeability of glomerulus
  • Impaired reabsorption of protein normally present in glomerular filtrate due to tubular disease
  • Blood or exudate of renal origin
• Post renal
  • Protein gains entrance to urine after it leaves the renal tubules by contamination with exudates or blood.
  • Marked haematuria
  • Inflammatory exudate
    • Pyelitis
    • Ureteritis
    • Cystitis
    • Urethritis
    • Urolithiasis
• Extra urinary causes
  • Blood or exudate from genital tract contaminates urine
  • Chronic passive congestion of kidneys
  • Neoplasms and emboli