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The Urine protein tests detect and measure protein being released into the urine. Normally,The elimination of proitein in urine is less than 150 mg/day and less than 30 mg of albumin/day. Elevated levels may be seen temporarily with conditions such as infections, stress, pregnancy, diet, cold exposure, or heavy exercise. Persistent protein in the urine suggests possible kidney damage or some other condition that requires additional testing to determine the cause.
Unlike the routine urine protein chemistry dipstick pad, the SSA reaction will detect globulin and Bence Jones proteins, in addition to albumin (although it is more sensitive to albumin). In alkaline urine, the SSA reaction is a more accurate measure of urine protein content than the dipstick.The most accurate measurement of urine protein output continues to be the 24hour urine protein usually performed by the Clinical Chemistry department of the clinical laboratory. Another good alternative to this test is the urine protein to creatinine ratio.
Principle:
- Based on the precipitation of urine protein by a strong acid, sulfosalicylic acid.
- Three percent (3%) Sulfosalicylic Acid (SSA reagent) is added to a small and equal volume of clear urine.
- The acidification causes precipitation of protein in the sample (seen as increasing turbidity), which is subjectively graded as trace, 1+, 2+, 3+ or 4+.
Procedure:
- Into a clear glass or plastic test-tube pour a small amount of urine supernatant Depending on the size of tube used, 1 mL urine will be required (the width of the tip of your little finger should do it.)
- Squirt an equal amount of 3% SSA (kept in the small bottles) into the tube directly on top of the urine.
- Shake tube gently with a quick flick and read for turbidity immediately.
RESULTS
OBSERVATION AND INTERPRETATION
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Clinical Significance:
Proteinuria is frequently seen in chronic diseases, such as diabetes and hypertension, with increasing amounts of protein in the urine reflecting increasing kidney damage. With early kidney damage, the affected person is often asymptomatic. As damage progresses, or if protein loss is severe, the person may develop symptoms such as edema, shortness of breath, nausea, and fatigue. Excess protein overproduction, as seen with multiple myeloma, lymphoma, and amyloidosis, can also lead to proteinuria.
Interferences:
False positives:
- X-ray contrast media
- High concentration of antibiotics, such as penicillin and cephalosporin derivatives
SSA test should always be performed on urine supernatant. Unless the urine sample is
clear, the test must be performed on centrifuged urine. Best practice is to always used
supernatant from a properly spun urine sample.
- Cloudy, uncentrifuged urine
False negatives:
- Highly buffered alkaline urine. (The urine may require acidification to a pH of 7.0 beforeperforming the SSA test.)
- Dilute urine
- Turbid urine - may mask a positive reaction. Again, best practice is to always used supernatant from a properly spun urine sample.
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