THE COMPLEX MULTI-SYSTEM SYMPTOM INVENTORY (COMSS): A NEW INSTRUMENT TO ASSESS SYMPTOM FREQUENCY, IMPACT, AND POSTURAL DEPENDENCE ACROSS MULTIPLE CENTRAL AND PERIPHERAL AUTONOMIC SYMPTOM DOMAINS

Background

Patients with mental health diagnoses often experience a high burden of cognitive and somatic symptoms alongside concurrent traditional psychiatric symptoms. Many of these can be captured by self-report measures that focus on symptoms commonly experienced by individuals with autonomic nervous system dysregulation. However, available symptom inventories were primarily developed for other applications (e.g., the COMPASS-31), focus on a subset of symptoms (e.g. orthostatic hypotension), and/or have anchor points that can be challenging to compare across patients or across time (e.g., the MALMO). Here, we report on the development and validation of a new 18-item self-report measure with 4 subdomains, designed for both clinical and research use in patients with complex, multi-system symptoms.

Methods

Development started by identifying 31 commonly occurring symptoms reported during autonomic testing and clinic visits at the University of Washington Autonomic Neurology Clinic. These 31 symptoms included central (e.g., problems with concentration or sleep) and peripheral (e.g., gastrointestinal, cardiovascular) symptom areas. Using a two-week lookback, symptoms were scored for frequency ranging from monthly or less (0) to multiple times daily (4). Symptoms occurring with a frequency of weekly or greater were additionally scored for bothersomeness, and a subset of commonly postural items scored for postural dependence. The questionnaire was implemented in Qualtrics as part of an existing clinical study and initial subject responses were gathered from January 2022-April 2024; this larger study also included 11 existing validated instruments, and assessed the presence or absence of 12 commonly occurring diagnoses with complex symptoms.

Results

The analyzed data set included 342 completed questionnaires (average age 45.7 + 13.3 years, 72% female). Prior to item-reduction, Cronbach’s alpha (0.95), item-to-item correlations, and item-to-total correlations suggested strong internal validity and moderate item redundancy. Following iterative correlation analysis and linear modeling to eliminate redundant items, an 18item measure that included both frequency and postural-dependence but no bothersomeness items was used to create the final CoMSS measure. Factor analysis of the final measure revealed a 4 factor structure, with factors roughly corresponding to postural symptoms (similar to core symptoms of postural orthostatic tachycardia syndrome [POTS]); symptoms of low energy, sleep and joint/muscle pain (similar to core symptoms of fibromyalgia and/or ME/CFS); gastrointestinal symptoms (similar to core symptoms of irritable bowl syndrome); and vasomotor, nightmares and anxiety symptoms (similar to a subset of core PTSD symptoms). Convergent validity for each factor and with concurrently administered validated instruments found Pearson’s coefficients ranging from 0.3-0.6, suggesting that the CoMSS is related to, but not redundant with, existing measures.

Conclusions

The novel CoMSS self-report instrument for complex, multi-system symptoms demonstrates strong psychometric properties, and reveals an underlying factor structure potentially similar to existing syndromic diagnostic categorizations.