Validation of a Pressure Pain Threshold Scale in Patients Diagnosed With Myofascial Pain Syndrome and Fibromyalgia
Condition: Myofascial Pain Syndrome; Fibromyalgia
MeSH terms: Fibromyalgia; Myofascial Pain Syndromes; Syndrome; Somatoform Disorders
Study type: Observational

Summary: 
      To date, there are no valid and reliable pressure pain threshold scales for use in research
      or clinical practice. The existing manual palpation protocols and scales have limited support
      in the literature and our knowledge has not advanced since these scales were proposed in the
      1990's. Therefore, the purpose of this investigation was to develop a valid and reliable PPTS
      in order to provide an objective means of assessing pressure pain thresholds and create a
      reliable method of communication among clinicians for individuals with a diagnoses
      characterized by MPS and FM. These conditions were chosen based on their high prevalence
      among chronic pain conditions and are also dependent upon the manual palpation examination
      for their diagnosis.
    

Detailed description: 
      The purpose of this investigation was to develop a valid and reliable PPTS in order to
      provide an objective means of assessing pressure pain threshold and to create a reliable
      method of communication among clinicians. Eighty-four participants (N=84) were enrolled in
      the study and assigned to three groups: FM (N=28), MPS (N=28), and control group (N=28).
      Participants were recruited from three sites. All participants were aged 18 to 65 years and
      met the inclusion criteria for 1 of the 3 groups. All participants were required to read,
      speak and write English as needed to complete forms and consent. The following criteria for
      each group was as follows:

        1. Control group: Individuals with no current or prior diagnosis consistent with MPS or FM.
           No current injuries or integumentary abnormalities at the designated palpation sites.

        2. MPS group: Individuals with a diagnosis of MPS that does not meet the American College
           of Rheumatology (ACR) diagnostic criteria for FM. No current injuries or integumentary
           abnormalities at the designated palpation sites.

        3. FM group: Individuals who met the criteria for a diagnosis of FM based upon the ACR
           diagnostic criteria. No current injuries or integumentary abnormalities at the
           designated palpation sites.

      Prior to testing, participants filled out a screening questionnaire with questions that
      represent the exclusion criteria which were used to determine ineligibility for this study.
      Participants who met the inclusion criteria and consented to participate were enrolled in the
      study. A California State University Dominguez Hills approved consent was read and signed by
      all participants prior to beginning data collection. Following consent, participant filled
      out a questionnaire to provide demographic information which included age, height, weight,
      arm dominance.

      Following completion of the paperwork, all participants underwent testing from the primary
      investigator which was conducted between the hours of 8 am and 2pm. Participants were
      instructed to refrain from taking any related medication (e.g. pain medication) prior to
      testing. All participants underwent the same testing procedures and were blinded from the
      examiner's scores and other participants enrolled in the study.

      For the reliability portion of the study, a total of 20 participants (10 MPS/FM and 10
      control group) underwent 2 days of testing. Each testing session lasted approximately 45
      minutes. After the reliability portion was complete, all other recruited subjects underwent 1
      day of testing which lasted approximately 45 minutes.

      The testing process consisted of 2-parts which were based upon the American College of
      Rheumatology (ACR) diagnostic criteria for FM. The protocol required the examiner to apply
      pressure to 18 pre-determined and 2 control points up to 4kg/cm2 at a rate of 1kg per second
      for a total of 4 seconds at each point, one time.12, 13 For Part I, the examiner applied a
      gradually increasing pressure using the thumb and digital pressure sensor at each
      pre-determined tender point. For Part II, the examiner applied a gradual increasing pressure
      using the algometer to the pre-determined tender points. For both Part I and II, the
      participant recorded their level of discomfort at each tender point using the MTPS and VAS
      pain scales once the examiner reached 4kg/cm2 of pressure or once a maximum level of pressure
      was felt. Participants were able to stop testing at any time. The examiner simultaneously
      recorded the patient's response using the PPTS scale for each tender point.

      Collected data was transferred to SPSS v.22 (IBM SPSS, Chicago, IL). Means, standard error of
      mean (SEM), 95% confidence intervals (95% CI), and ranges of the descriptive data from each
      group was calculated. Group differences were calculated using the independent t-test. Six
      clinical questions were measured in this investigation which required specific parametric and
      non-parametric (ordinal data) statistical calculations. The P-value was considered
      significant at the .05 level using a two-tailed test (α2 =.05) for all clinical questions.
    

Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        3 groups of participants were recruited for this study:

          -  Control group: Individuals with no current or prior diagnosis consistent with
             Myofascial Pain Syndrome (MPS) or Fibromyalgia (FM).

          -  MPS group: Individuals with a diagnosis of MPS that does not meet the American College
             of Rheumatology (ACR) diagnostic criteria for FM.

          -  FM group: Individuals who met the criteria for a diagnosis of FM based upon the ACR
             diagnostic criteria.
      
Keywords: Palpation; Chronic Pain; Muscle