Shelf life of fluorescent treponemal antibody-absorption test reagents.

Properly prepared, standarized, and stored fluorescent treponemal antibody-absorption (FTA-ABS) reagents have been shown to have stabilities equal to other biological reagents. A liquid antigen over 10 years old has been shown to give a satisfactory reaction. Newer preparations have now been shown to be stable for over 5 years, and the tests on each are being continued. The very new liquid antigens which were originally standardized by the FTA-ABS method have shown no decrease in potency over a 20-month period. Stability studies on antigens dried on slides are now in their eighth month, with no apparent loss in potency. The stability of the conjugate is constant when stored frozen at -20 C or lyophilized. When stored as a liquid at 4 C, the stability is governed by the pH and the molarity of the buffer. The standardized and lyophilized sorbent has been shown to be stable for over 1 year.