Interobserver Variability in the Measurement of Diastolic Blood Pressure in Pregnancy

Abstract

Objective: The objective of this study was to evaluate and compare the magnitude of interobserver variability present when measuring Korotkoff phase 4 versus phase 5 in pregnant women.

Methods: Three observers with different backgrounds simultaneously measured both phase 4 and phase 5 on 98 gravidas. Data were used to estimate detectability rates, perform an analysis of variance to assess interobserver variability, examine the distribution of interobserver differences, and evaluate the magnitude of the difference between the two diastolic end points.

Main Outcome Measures: Detectability rates of phase 4 and phase 5 diastolic pressure and measures of interobserver variability in diastolic readings.

Results: Detectability rates were observer dependent, ranging from 81% to 96% for phase 4 and from 79% to 85% for phase 5. Analysis of variance demonstrated similar degrees of interobserver variability for both end points. Likewise, for any two observers measuring either end point, there was a similar number of measurements that differed by at least 8 mm Hg. Lastly, the median difference between the two end points was estimated to be 6-12 mm Hg, depending on the observer.

Conclusions: These results do not convincingly favor use of either Korot-koff 4 or Korotkoff 5 in pregnancy. Detectability rates differ among observers and interobserver variability in measurement of blood pressure is significant; improved training for all is suggested.

Key Words:

• Blood pressure determination
• Interobserver variation
• Pregnancy