[The Preservation of HBV, HCV, HIV Viral Nucleic Acids in Plasma by Dry Spot Method and the Duration of Preservation].

Objective: To establish a method for preserving viral nucleic acids in plasma using a blood collection card based on the dry spot method, to predict the duration of nucleic acid preservation by establishing the Arrhenius equation, and to demonstrate the feasibility of this preservation method for the re-testing of nucleic acids in blood samples retained by blood banks.

Methods: Plasma samples positive for HBV, HCV, and HIV nucleic acids were prepared into preservation cards in the form of dry plasma spots for storage. The prepared preservation cards were placed under accelerated storage conditions at 37, 45, 50, and 55 ℃. The preservation cards were periodically retrieved from each temperature condition for nucleic acid extraction, and the nucleic acid samples were purified for subsequent PCR testing, with the recorded CT values. An Arrhenius equation model was established between the expiration time and the storage temperature, thereby predicting the validity period of nucleic acid preservation in blood collection cards under specified storage temperature conditions.

Results: For the plasma samples positive for HBV, HCV, and HIV nucleic acids preserved using the dry spot method, the regression equations for the duration with temperature were as follows: y=-11546 x + 31.74 for HBV, y=-12949x + 36.88 for HCV, and y=-12204x + 34.48 for HIV, with the correlation coefficient r greater than 0.98 for all. It was predicted that at a storage temperature of 4 ℃, the preservation periods for HBV, HCV, and HIV viral nucleic acids using the dry spot method would be 20 792 days, 19 289 days, and 14 285 days, respectively. At a storage temperature of 20 ℃, the preservation periods would be 2 135 days 1 502 days, and 1 289 days, respectively.

Conclusion: The nucleic acids of the three common viral pathogens in blood samples, when preserved using the dry spot method, conform to a first-order reaction pattern in the accelerated degradation experiment. The relationship between the rate of nucleic acid degradation and the absolute temperature of storage is consistent with the Arrhenius equation. Based on the calculations using this equation, the stability and validity period of plasma nucleic acid samples preserved using the dry spot method can reach a minimum of 3.5 years under storage conditions not exceeding 20 ℃, which essentially meets the requirements for the preservation period of blood samples retained by blood banks.