What types of clients and professionals can you generalize these results to? Is this concept internal or external validity?
  • The following vignette is from: Rozenfeld, 2017. Test-retest reliability of myofascial trigger point detection in hip and thigh areas.

BACKGROUND: Myofascial trigger points (MTrP’s) are a primary source of pain in patients with musculoskeletal disorders. Reliable MTrP palpation is necessary for their diagnosis and treatment.

OBJECTIVE: To evaluate intra- and inter-rater reliability of MTrP recognition in hip and thigh muscles.

DESIGN: Reliability study.

SUBJECTS: 21 soldiers and officers referred to a military outpatient clinic in Israel (15 males and 6 females, mean age 21.1 years) with lower extremity musculoskeletal pain. Inclusion criteria: 18-30 years old. Exclusion criteria: history of fibromyalgia.

METHODS: Two experienced physical therapists performed the examinations and were blinded to the subject medical condition and previous MTrP evaluation. Each subject was evaluated four times (twice by each examiner) in a random order. The evaluation was performed on both legs and included a total of 16 locations in several areas of the quadriceps and gluteus muscles.

STATISTICS: The outcome of current presence of a MTrP was dichotomous (yes, no). Kappa was used to determine intra-rater reliability for each physical therapist (intra-rater reliability) and between physical therapists (inter-rater reliability)

RESULTS: Below are Kappa values for different areas of the quadricep muscle.

Physical Therapist 1    Physical Therapist 2    Inter-rater

Rectus femoris            -0.04                            -0.02                            -0.04

Middle VMO                 0.66*                            0.77*                            0.64*

Distal VMO                  0.53*                            0.73*                            0.73*

Middle VL                    -0.02                            0.23                             -0.04

Distal VL                      0.46*                            0.64*                            0.63*

* p<0.05

VL=vastus lateralis; VMO=vastus medialis oblique

Answer the following questions based on the above results:

  1. What statistical test was accomplished by having each physical therapist perform two exams on each subject?
  2. Which physical therapist demonstrated higher intra-rater reliability?
  3. Which muscle demonstrated the highest inter-rater reliability?
  4. If a physical therapist had limited time to perform a clinical exam for active MTrP in the hip and thigh muscles, what specific areas would you recommend?
  5. What types of clients and professionals can you generalize these results to? Is this concept internal or external validity?