Research characterizes the Clinical Lost-in-the-Middle (CLitM) effect, where LLMs struggle to retrieve critical information located in the center of long electronic health records. Using MedAlign on 2,196 pairs across six models, the study found a 21.9 percentage-point accuracy gap between peak performance in the outer deciles and the trough in the 70-80% range. This central retrieval failure poses a significant risk for clinical reasoning tasks where key facts often reside in the middle of lengthy patient notes. The authors compare various context-selection strategies to mitigate this degradation in reliability.
- LLMs lose ~22% accuracy on facts in the center of long EHRs vs edges.
- CLitM is a distinct, measurable risk for clinical decision support systems.
- Context-selection strategies are being evaluated to fix central retrieval gaps.
- Validation on MedAlign suggests this affects multiple model architectures.