PEM Severity Score: An Interactive Explorer

About the App

This application visualizes the computation of the PEM Severity Score (PSS), a metric that quantifies the severity of post-exertional malaise (PEM). The app allows the user to rate five symptoms by their respective frequency and severity and watch the score be derived step by step.

Workflow

The five symptom questions are taken from the DSQ-PEM (Cotler et al., 2018), each rated on two 0-4 scales. The PSS is the average of the per-question harmonic means of frequency and severity, normalized to a 0-1 range. Based on the result, a severity state is derived. Computation follows these four steps:
1. Feasibility: At least three of five questions must be fully answered.
2. Necessity: Based on the evaluation guidelines of the DSQ-PEM, PEM is present only if at least one question has frequency ≥ 2 and severity ≥ 2. Otherwise the PSS is set to 0.
3. Calculation: The answered questions are combined into the score.
4. Categorization: The score is mapped onto four severity states: not affected (=0), mildly affected (< 0.5), moderately affected (< 0.75) and severely affected (≤ 1.0). A gauge visualizes this aspect.

References

Cotler, J., Holtzman, C., Dudun, C. & Jason, L. A. A brief questionnaire to assess post-exertional malaise. Diagnostics 8, 66 (2018).