Statistical analysis of anti‐mamushi venom serum injection time and clinical course

A: The distribution of antiserum injection time. The antiserum injection is quite delayed in the severe cases. B: An ROC curve. Fourteen h is a favorable cut‐off for the antiserum injection timing that distinguishes non‐severe and severe cases. C: The relationship between the antiserum injection timing and the final grades. The final grade increased as the antiserum injection timing was delayed. Aim Early injection of anti‐mamushi venom serum (antiserum) is believed to be effective for the treatment of patients with mamushi bites. However, there is no firm information that indicates the time range constituting “early” injection. We tried to quantify the cut‐off time of antiserum injection that brings favorable clinical courses by clarifying the relationship between the injection time and clinical outcome. Methods We retrospectively analyzed the relationships between the time after bite, injection time of the antiserum, swelling grades, and laboratory values. Results The injection time of the antiserum in severe cases was significantly delayed as compared with non‐severe cases. The best cut‐off time of the antiserum injection that could distinguish non‐severe and severe cases was 14 h. In the group that received the antiserum within 14 h, the antiserum injection may have successfully arrested the grade progression in a substantial number of cases. In the other group receiving the antiserum beyond 14 h, the grades in many cases possibly may have peaked by the time of antiserum injection. Conclusion The cut‐off time of early injection for favorable clinical course was determined to be 14 h. A statistical basis concerning the appropriate antiserum injection time was made to help prevent a severe clinical course due to delayed injection.