Introduction

When a single gene exhibits an insignificant association with complex disease, applying gene-gene interactions as biomarkers may achieve striking findings. However, it is still a barrier to measuring the degree of gene-gene interaction at the individual level.

Therefore, we define iCKI, individual co-expression-like index. iCKI makes co-expression variations as novel individual biomarkers possible, enabling advanced applications in disease diagnosis, survival analysis, and more. Applying iCKI to rheumatoid arthritis early prediction and pancreatic cancer survival analysis, we demonstrated that co-expressions achieved substantial improvements compared to single biomarkers. Overall, iCKI offers an innovative and efficient indicator for considering gene-gene interactions as biomarkers and represents a starting point for individual co-expression.