Validation of a Pressure Pain Threshold Scale in Patients Diagnosed with Myofascial Pain Syndrome and Fibromyalgia

Background: Palpation is an examination technique used to diagnose and treat myofascial pain syndrome (MPS) and fibromyalgia (FM). Currently, there is no validated technique for classifying the results. A valid and reliable pressure pain threshold scale (PPTS) may provide a means for clinicians to grade, document, and report findings. The purpose of this dissertation was to validate a PPTS in patients diagnosed with MPS and FM. Design and Methods: An observational study. Participants who met the inclusion criteria were placed into three equal groups: MPS, FM, and control. All participants underwent one, two-part testing sessions using the American College of Rheumatology criteria. Part-I consisted of palpation with a digital pressure sensor and part-II utilized an algometer. For each tender point (18-total), the participants graded their level of discomfort using the visual analog scale (VAS) and manual tender point rating survey (MTPS) and the examiner graded their response using the PPTS (e.g. ordinal scale with increasing severity from 0-4). Analysis: Intrarater reliability was calculated using the intraclass correlation coefficient model 3, k. Concurrent validity between the PPTS, VAS, and MTPS was calculated using the spearman rank correlation coefficient. A receiver operating characteristic curve was used to determine the minimal cut-off value between groups. Results: Eighty-four participants were included in the analysis. The PPTS had good intrarater reliability (ICC ≥.88). A moderate to excellent relationship was found between the PPTS and VAS for all groups with the algometer and digital pressure sensor (rho ≥.61). A moderate to excellent relationship was found between the PPTS and MTPS for all groups with the algometer (rho≥.68) and for the MPS and control group with the digital pressure sensor (rho ≥.71). There was a little to moderate relationship (rho=.01-.50) between the PPTS and MTPS for the FM group with the digital pressure sensor. A cut-off value of 2 on the PPTS differentiated participants with MPS and FM from controls. Discussion: The results provide preliminary evidence validating the PPTS for patients with MPS and FM. Future research should determine interrater reliability, diagnostic accuracy, and efficacy of the PPTS with other chronic pain and orthopedic conditions.