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Urine TGF- β1 Assay Validation: Spinning Down Urine Samples Could Diminish TGF-β1 Signal by Igor Y. Pavlov, Fuad Shihab, Julio C. Delgado

Background: TGF-β1 is a mediator of immune and anti-inflammatory responses. The present research was dedicated to the validation of the urine Quantikine Human TGF-β1 ELISA assay.
Methods: A reference interval was developed utilizing 100 urine samples from healthy donors. Samples containing precipitate were centrifuged and supernatants or unspun specimens were run with TGF-β1 assay.
Results: Supernatant TGF-β1 concentrations are only a fraction of the unspun sample values (77 % to 29 %, even less for the low concentration samples). Validation involving uncentrifuged urine samples demonstrated the following TGF-β1 assay characteristics: linearity from 23 to 1286 pg/mL, recovery from 95 to 116 %; precision: <17 %; analytical specificity 3 pg/mL; reference interval from 0 to 39 pg/mg creatinine; freeze-thaw stability: af-ter first thawing, urine samples could loose from 5 to 40 % of TGF-β1 activity on each following freeze-thaw circle.
Conclusions: For TGF-β1 assay, urine sample preparation should not include a centrifugation step; repeating freeze-thawing should be avoided.

DOI: Clin. Lab. 2011;57:1027-1029