Assessing the effect of multiple freeze-thaw cycles on the stability of serum samples for anti-HIV antibody detection

Abstract

The present study investigated the impact of multiple and consecutive freeze-thaw cycles on the reactivity of anti-HIV antibodies in stored serum samples by using different methodologies for detecting the specific antibodies. The analyzed sera were part of serum panels (comprised of anti-HIV positive and negative samples), produced at the Center of Immunology – Instituto Adolfo Lutz, which have been the reference specimens for producing internal quality assurance sera of HIV/Aids immunodiagnostic assays. After performing every step of 11 consecutive and multiple freeze-thaw cycles procedure (varying from 7 to 60 cycles), the HIV antibody reactivity in the respective sera was evaluated by means of EIA/ELISA, Western blot and indirect immunofluorescence methodologies. No statistically significant effect on the specific antibody reactivity was found in sera after completing the freeze-thaw process up to 60 cycles. Neither false-negative reactions in HIV antibody positive sera, nor false-positive results in HIV-negative samples were detected.