title: Comparison between a newly developed PC-based Doppler umbilical artery waveform analyser and a commercial unit.
abstract: OBJECTIVE
  To determine the accuracy of the resistance index (RI) of flow velocity waveforms of the umbilical artery measured using a newly developed PC-based continuous wave Doppler device (Umbiflow) with regard to systematic and random variations when compared with a commercial standard (Vasoflow).
  
  
  METHODS
  A cohort study.
  
  
  METHODS
  The fetal evaluation clinic (FEC) at Tygerberg Hospital.
  
  
  METHODS
  Patients referred to the FEC at Tygerberg Hospital with suspected chronic placental insufficiency.
  
  
  METHODS
  The correlation coefficients indicating the strength of the relationship between the two devices and their agreement using the method of Bland and Altman.
  
  
  RESULTS
  A total of 248 patients were studied. The mean RIs of the first Doppler assessment were 0.69 (standard deviation (SD) 0.11) and 0.67 (SD 0.11) using the Vasoflow and Umbiflow respectively. The Pearson's correlation coefficient comparing the RI of the first test was 0.85. The degree of agreement between the two methods was excellent, the mean differences being very small (< 0.024) with tight confidence intervals. One hundred and ninety-four patients (78.2%) of patients remained in the same percentile category with both the Vasoflow and Umbiflow.
  
  
  CONCLUSIONS
  The accuracy of the Umbiflow has been proved. A non-significant trend towards slightly lower values needs to be considered. This could be addressed by changing the percentile cut-off to slightly lower values.
authors.affiliation: Department of Obstetrics and Gynaecology, Stellenbosch University, Tygerberg, W Cape.
authors.forename: G B
authors.initials: GB
authors.lastname: Theron
authors.forename: A M
authors.initials: AM
authors.lastname: Theron
authors.forename: H J
authors.initials: HJ
authors.lastname: Odendaal
authors.forename: A E
authors.initials: AE
authors.lastname: Bunn
mesh_terms: D015331:Cohort Studies; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D008403:Mass Screening / Q000295:instrumentation; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D018608:Ultrasonography, Doppler / Q000295:instrumentation* / Q000379:methods; D016216:Ultrasonography, Prenatal / Q000295:instrumentation* / Q000379:methods; D014469:Umbilical Arteries / Q000000981:diagnostic imaging*