title: Interrater and intrarater reliability of transverse abdominal and lumbar multifidus muscle thickness in subjects with and without low back pain.
abstract: METHODS
  Two-group, repeated-measures reliability study.
  
  
  OBJECTIVE
  To determine interrater and intrarater reliability of ultrasound measurements of transverse abdominal (TrA) and lumbar multifidus (LM) muscle thickness, during rest and contraction, in subjects with low back pain (LBP) and healthy subjects over 3 consecutive days, performed by an experienced and a novice rater.
  
  
  BACKGROUND
  Previous reliability studies of TrA or LM thickness did not simultaneously account for muscle state, rater experience, and multiday assessment in large subject samples.
  
  
  METHODS
  The 2 raters measured TrA and LM thickness on 3 consecutive days in 42 healthy subjects and 56 subjects with LBP, during rest and contraction, and calculated the percent thickness change from rest to contraction. Intraclass correlation coefficients (ICC(2,k)) and 95% minimal detectable change in thickness were derived for a single measure (day 1) and an average measure (days 1-3).
  
  
  RESULTS
  The interrater ICC(2,1) values for single-measure thickness (LBP group, 0.71-0.87; healthy group, 0.94-1.00) were similar to those for average-measure thickness (LBP group, 0.73-0.84; healthy group, 0.93-1.00). Both interrater ICC(2,1) and ICC(2,3) were lower for the relative thickness change (0.61-0.96). Intrarater ICC(2,1) values across 3 consecutive days were high for both raters across the 2 groups (LBP group, 0.95-1.00; healthy group, 0.93-1.00), albeit lower for the relative thickness change (0.79-0.99). The 95% minimal detectable changes were < 0.3 mm for the TrA and < 2 mm for the LM (but, in most cases, less than 10% of average thickness).
  
  
  CONCLUSIONS
  Both experienced and trained novice raters provided reliable measurements of TrA and LM thickness in participants with LBP and healthy participants, during rest and contraction. One-time measurements were similar to averaged measurements. Small absolute errors were observed. Public trial registry: Australian New Zealand Clinical Trials Registry ACTRN12613001077752.
authors.affiliation: Clinic for Rehabilitation Dr M. Zotovic, Belgrade, Serbia.
authors.forename: Olivera
authors.initials: O
authors.lastname: Djordjevic
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Djordjevic
authors.forename: Ljubica
authors.initials: L
authors.lastname: Konstantinovic
mesh_terms: D000009:Abdominal Muscles / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000473:pathology; D000328:Adult; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D064170:Paraspinal Muscles / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012146:Rest; D014463:Ultrasonography
keywords: assessment; rehabilitation; reproducibility of measurements; trunk; ultrasonography