When more than trace amounts of protein are found in urine, this is termed proteinuria. Detection of proteinuria is an important indicator of renal disease because protein has a very low maximal tubular rate of reabsorption. The following methods are used to test for proteinuria:
- Heat and acetic acid test
- Sulphosalicyclic acid test
- Hellers nitric acid test
- Esbach’s method
- Aufrecht’s method
- Protein reagent strip test
- Biuret test
- Urine protein electrophoresis
Heat and acetic acid test
This test is based on the principle that proteins get precipitated when boiled in an acidic medium.
- Take 5-10ml clear urine in a test tube.
- Boil the upper portion over a flame.
- Compare the heated part with the lower part. Cloudiness or turbidity indicates the presence of either proteins or phosphates/carbonates.
- Add 2-4 drops of 10% glacial acetic acid and boil the upper portion again.
- If turbidity is still present, protein is present in urine. If turbidity disappears, that is due to phosphates or carbonates present in urine.
Result and Interpretation:
Grade the turbidity as follows:
- Negative : No cloudiness
- Trace: Barely visible cloudiness.
- 1+ : definite cloud without granular flocculation
- 2+ : heavy and granular cloud without granular flocculation
- 3+ : densed cloud with marked flocculation.
- 4+ : thick curdy precipitation and coagulation
- Sood R. Concise book of Medical Laboratory Technology. Jaypee Brothers Pvt. Limited; 2015.
- Cheesbrough M. Medical laboratory manual for tropical countries. M. Cheesbrough, 14 Bevills Close, Doddington, Cambridgeshire, PE15 OTT.; 1981.