title: How many measurements are needed for liver stiffness assessment by 2D-Shear Wave Elastography (2D-SWE) and which value should be used: the mean or median?
abstract: OBJECTIVE
  To analyze how many measurements are needed for non-invasive assessment of liver stiffness (LS) by means of 2D-Shear Wave Elastography (2D-SWE) and if the use of mean of median values of 2D-SWE measurements is needed.
  
  
  METHODS
  We evaluated 449 consecutive subjects (with or without chronic liver disease) by means of Transient Elastography (TE) and 2D-SWE. We compared the correlation of LS assessed by TE with 2D-SWE measurements when using either the median of 5 valid 2D-SWE measurements or the mean of 3 or 5 valid 2D-SWE measurements.
  
  
  RESULTS
  We obtained reliable LS measurements by TE in 330/449 subjects (73.5%). From these, in 281 subjects we obtained 5 valid 2D-SWE measurements. The correlation of LS assessed by TE with 2D-SWE values was similar when we used the median value of 5 valid 2D-SWE measurements, the mean value of 5 valid 2D-SWE measurements or the mean value of 3 valid 2D-SWE measurements: r =0.683, r=0.711 and r=0.691, respectively. There were no significant differences between the median value of 5 valid 2D-SWE measurements; the mean value of 5 valid 2D-SWE measurements; or the mean value of 3 valid 2D-SWE measurements: 7.6 kPa, 7.7 kPa and 7.6 kPa, respectively.
  
  
  CONCLUSIONS
  Our study showed that it is enough to perform 3 valid 2D-SWE measurements and to use the mean value of these measurements.
authors.affiliation: Department of Gastroenterology and Hepatology, "Victor Babes" University of Medicine and Pharmacy, Timisoara, Romania; Email: bota_simona1982@yahoo.com.
authors.forename: Ioan
authors.initials: I
authors.lastname: Sporea
authors.forename: Oana
authors.initials: O
authors.lastname: Grădinaru-Taşcău
authors.forename: Simona
authors.initials: S
authors.lastname: Bota
authors.forename: Alina
authors.initials: A
authors.lastname: Popescu
authors.forename: Roxana
authors.initials: R
authors.lastname: Şirli
authors.forename: Ana
authors.initials: A
authors.lastname: Jurchiş
authors.forename: Mădălina
authors.initials: M
authors.lastname: Popescu
authors.forename: Mirela
authors.initials: M
authors.lastname: Dănilă
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002908:Chronic Disease; D003627:Data Interpretation, Statistical; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008107:Liver Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D033081:Shear Strength; D013314:Stress, Mechanical; D055815:Young Adult