Urine Protein: SSA
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"PROT-SSA" represents the reaction observed on the sulfosalicylic acid (SSA) precipitation test. The SSA reagent is added to a small volume of urine. Acidification causes precipitation of protein in the sample (seen as increasing turbidity), which is subjectively graded as trace, 1+, 2+, 3+ or 4+.
Unlike the "PROT-STIX" test, the SSA reaction will detect albumin and globulins (although it is more sensitive to albumin). In addition, the SSA detects Bence-Jones proteins, although it often underestimates them.
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 is measurement of urine protein excretion over 24-hours. A good alternative to this test is the urine protein to creatinine ratio.

False positives
  • Contrast media
  • Antibiotics in high concentration, e.g. penicillin and cephalosporin derivatives
  • Uncentrifuged turbid urines can look positive. Therefore, SSA should always be performed on urine supernatant.
False negatives
  • Highly buffered alkaline urine. The urine may require acidification to a pH of 7.0 before performing the SSA test.
  • Dilute urine
  • Turbid urine - may mask a positive reaction.

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Last Updated: Friday, January 15th 1999