Predictive Criterion Validity of the Parsley Symptom Index Against the Patient-Reported Outcomes Measurement Information System-10 in a Chronic Disease Cohort: Retrospective Cohort Study (Preprint)

Abstract

BACKGROUND Approximately 60% of US adults live with chronic disease, imposing a significant burden on patients and healthcare systems. With the rise of telehealth, Electronic Patient-Reported Outcomes Measures (ePROMs) have emerged as pivotal tools for managing chronic disease. While numerous ePROMs exist, few have been designed explicitly for telehealth settings. The Parsley Symptom Index (PSI) is an ePROM developed for a virtual telehealth environment that seeks to address this gap. OBJECTIVE This study aimed to externally validate the PSI in a functional medicine clinic serving chronic disease patients. We sought to determine 2 items: (1) whether the PSI predicts changes in the established Patient-Reported Outcomes Measurement Information System 10-Question Short Form (PROMIS-10 Global Health), and (2) whether this relationship is moderated by disease severity. METHODS We conducted a retrospective cohort study using data from 367 unique patients, amassing 1,170 observations between August 30, 2017, and January 30, 2023. Patients completed the PSI and the PROMIS-10 multiple times throughout the study period. Using correlation and regression analyses, we explored the relationship between PSI and PROMIS-10 scores and examined the moderating effect of disease severity on this relationship. RESULTS Our study revealed significant relationships between the PSI and PROMIS-10 physical and mental health scores through comprehensive univariate analyses, thus establishing support for the criterion validity of the PSI. These analyses highlighted the PSI’s potential as an insightful tool in understanding and predicting both mental and physical health dimensions. CONCLUSIONS Our findings emphasize the importance of the PSI in capturing the nuanced interactions between symptomatology and health outcomes, regardless of the definition of severity level. The strong correlations in the high-severity group, defined by both PROMIS-10 and PSI, underscore the substantial connection between symptom severity and both physical and mental health. These insights reinforce the value of the PSI in diverse clinical contexts and support its potential as a versatile tool in both research and practice.