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Percent difference in HIV-1 RNA detection between one and three freeze-thaw cycles. The RNA equivalents per milliliter after the first freeze-thaw cycle, which is considered the baseline value, are given beneath the white columns (freezing at −20°C) and beneath the black columns (freezing at −80°C; numbers in brackets). HIV-1 RNA was detected by the Chiron bDNA assay (37).
