Virucidal activity of formaldehyde solutions used for preservation of allograft tympano-ossicular systems

ABSTRACT

Objective: Allograft tympano-ossicular systems (ATOS) can provide superior outcomes in particular circumstances, for example, in case of a need for total reconstruction of the eardrum and chain. ATOS are preserved in a 2.7%–4% formaldehyde solution after procurement at room temperature (15-25°C) for 2–5 days, followed by 4 °C for a total storage of at least 14 days. This study aimed to review the literature on the virucidal effect of formaldehyde on viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: Narrative review of the literature available on the virucidal effect of formaldehyde, as searched in the scientific database PubMed. Results: Both free and intracellular HIV as well as HBV and HCV are significantly reduced at low concentrations of formaldehyde and short exposure time. Factors increasing the effectivity of formaldehyde solutions are high concentration, long exposure time, and high temperature. It has been demonstrated that HIV-infected allografts are disinfected by formaldehyde preservation. No case of HIV, HBV, or HCV transmission through ATOS has been reported. Coronaviruses closely related to SARS-CoV-2, such as SARS-CoV and MERS-CoV, are inactivated by low concentrations of formaldehyde solution, even at short exposure times. Conclusion: These findings indicate that formaldehyde is effective in inactivating HIV, HBV, HCV, and coronaviruses. ATOS are stored in a high concentration formaldehyde solution for a long period. The applied preservation method of ATOS, including temporary storage at room temperature, should be maintained for effective inactivation. The formaldehyde preservation method in combination with donor screening and serological and nucleotide amplification testing make ATOS a very safe reconstruction material.