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Intraobserver and interobserver variability of the amniotic fluid index
J P Bruner1, G W Reed, A P Sarno
1Department of Obstetrics and Gynecology, Tripler Army Medical Center, Honolulu, Hawaii.
Objective:
We assessed intraobserver and interobserver variations in the performance of the amniotic fluid index.
Study Design:
A total of 34 women in the third trimester with intact membranes were examined twice by each of three examiners. The amniotic fluid index was measured once by each of the three examiners in order, then repeated by each examiner in the same order. Numeric displays on the video terminal screen were covered so that the examiners were blinded to actual measurement values. Results were recorded on hard copy for later data analysis. A senior investigator supervised all examinations to monitor consistency of technique.
Results:
Overall, the coefficient of variation for amniotic fluid index measurements varied from 10.8% within examiners to 15.4% between examiners. Both between and within variation of absolute differences increased as the amniotic fluid index value increased, while the percent difference decreased. Simply repeating the test by the same examiner will decrease the coefficient of variation significantly.
Conclusion:
Although intraobserver and interobserver variability cannot be eliminated, its impact can be minimized by use of the same examiner for serial studies.