title: Intraobserver variability in fibroid size measurements: estimated effects on assessing fibroid growth.
abstract: OBJECTIVE
  To evaluate intraobserver variability of fibroid sonographic measurements and apply this factor to fibroid growth assessment.
  
  
  METHODS
  Study participants were African American women aged 23 to 34 years who had never had a diagnosis of uterine fibroids. All participants underwent transvaginal sonography to screen for the presence of previously undiagnosed fibroids (≥0.5 cm in diameter). The diameters of up to 6 fibroids were measured in 3 perpendicular planes at 3 separate times during the examinations by experienced sonographers. Intraobserver variability as measured by the coefficient of variation (CV) for fibroid diameter and volume was calculated for each fibroid, and factors associated with the CV were assessed by regression models. The impact of variability on growth assessment was determined.
  
  
  RESULTS
  Ninety-six of 300 women screened were found to have at least 1 fibroid, yielding a total of 174 fibroids for this analysis. The mean CV for the 3 measurements of fibroid maximum diameter was 5.9%. The mean CV for fibroid volume was 12.7%. Fibroid size contributed significantly to intraobserver variability (P = .04), with greater variability for smaller fibroids. Fibroid type (submucosal, intramural, or subserosal) was not important. Fibroids from the same woman tended to have similar measurement variability when assessed for volume but not for maximum diameter. Calculations showed that when following up fibroids, as much as a 20% increase in diameter could be due to measurement error, not "true growth."
  
  
  CONCLUSIONS
  A small fibroid must have a greater change in size than a large fibroid to conclude that it is growing, but even for small fibroids an increase in diameter of greater than 20% is likely to indicate true growth, not measurement variability.
authors: Epidemiology Branch (M.M., D.B.) and Biostatistics Branch (S.D.P.), National Institute of Environmental Health, Research Triangle Park, North Carolina USA; and Department of Radiology, Division of Ultrasound, Henry Ford Health Systems, Detroit, Michigan USA (T.C.).
authors: Malana
authors: M
authors: Moshesh
authors: Epidemiology Branch (M.M., D.B.) and Biostatistics Branch (S.D.P.), National Institute of Environmental Health, Research Triangle Park, North Carolina USA; and Department of Radiology, Division of Ultrasound, Henry Ford Health Systems, Detroit, Michigan USA (T.C.).
authors: Shyamal D
authors: SD
authors: Peddada
authors: Epidemiology Branch (M.M., D.B.) and Biostatistics Branch (S.D.P.), National Institute of Environmental Health, Research Triangle Park, North Carolina USA; and Department of Radiology, Division of Ultrasound, Henry Ford Health Systems, Detroit, Michigan USA (T.C.).
authors: Tracy
authors: T
authors: Cooper
authors: Epidemiology Branch (M.M., D.B.) and Biostatistics Branch (S.D.P.), National Institute of Environmental Health, Research Triangle Park, North Carolina USA; and Department of Radiology, Division of Ultrasound, Henry Ford Health Systems, Detroit, Michigan USA (T.C.). baird@niehs.nih.gov.
authors: Donna
authors: D
authors: Baird
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007889:Leiomyoma / Q000000981:diagnostic imaging* / Q000473:pathology; D015588:Observer Variation; D014463:Ultrasonography; D014594:Uterine Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014599:Uterus / Q000000981:diagnostic imaging; D055815:Young Adult
keywords: coefficient of variation; fibroid; growth; gynecologic ultrasound; sonography; variability