CSS-SR Validation Study

Complex Regional Pain Syndrome (CRPS) is a chronic pain condition characterized by spontaneous pain, allodynia and hyperalgesia, edema, vasomotor and sudomotor changes, and motor and trophic changes. It usually begins regionally in a single limb after injury or surgery, and inflammatory, autonomic, and central mechanisms all appear to contribute to differing degrees. There are currently no treatments for CRPS proven effective in large scale clinical trials.

CRPS is considered an orphan condition by the U.S. Food and Drug Administration, and as such, acquiring adequate sample sizes for definitive clinical trials is challenging. One barrier to recruitment into CRPS research studies is the need to conduct in-person evaluations to screen for presence of current CRPS clinical features and determine CRPS diagnostic status. Unlike conditions such as chronic low back pain, which can be identified with high accuracy based on questions that can be administered remotely (i.e., pain intensity, location, frequency, and impact), diagnosing CRPS using the 2012 International Association for the Study of Pain (IASP) criteria (i.e., the Budapest criteria) requires that a history and physical examination be conducted. This situation is similar to that formerly encountered in fibromyalgia studies prior to publication of the modified American College of Rheumatology 2010 criteria (i.e., diagnosis was based on clinical tender point evaluation), a barrier ultimately overcome by publication of the validated 2010 self-report diagnostic screening criteria that could be administered remotely.

Our collaborators developed a self-report measure suitable for remote delivery to assess CRPS-related symptoms. They evaluated the diagnostic accuracy of a self-report version of the CRPS Severity Score (CSS-SR) and assessed its validity relative to the original CSS based on clinician evaluation (CSS-Clinician) in 112 patients undergoing total knee arthroplasty (TKA). In this study we will recruit patients with pain in an extremity at the outpatient chronic pain clinic at 75th street and will ask patients to complete the CSS-SR while the clinician evaluates the participant against the Budapest CRPS diagnosis criteria per usual care. Data (no identifiers) will be shared with our collaborator who will analyze and combine the findings from his TKA cohort with our outpatient chronic pain cohort to understand the external validity of the CSS-SR.

The proposed content of the self-report version of the CSS (CSS-SR) was rationally developed by creating lay language items designed to parallel the diagnostic symptoms assessed in the standardized clinician-obtained history that provides the basis for the symptom component of the CSS-Clinician. Thirteen questions in yes/no (presence/absence) checklist format assess presence of symptoms in the following areas: more prolonged or severe pain than expected, allodynia/hyperalgesia, skin temperature changes, skin color changes, edema, sweating changes, trophic changes (skin, hair, nails), tremor, dystonia, weakness, and range of motion limitations.

Scoring of the CSS-SR parallels scoring of the CSS-Clinician, with items coded as 1 for "Yes" and 0 for "No", with responses summed to create a total CSS-SR score potentially ranging from 0-13.

For the current validation study, CSS-SR items referred specifically to the "affected limb" to ensure that participants describe symptoms in the same body region as reflected in the assessment used to derive the CSS-Clinician.

Inclusion criteria

• 18 years of age or older
• Suspected or diagnosed with unilateral CRPS type I or II of the upper or lower extremity
• Suspected or diagnosed with non-CRPS-related pain of the upper or lower extremities

Exclusion criteria

• Bilateral CRPS
• Total knee arthroplasty as the inciting event of CRPS
• Less than 18 years of age
• Non-English speaking
• Inability to comprehend study protocol and questionnaires