Interrater reliability and effect of state on blood pressure measurements in infants 1 to 3 years of age

Abstract

Objective: The objective of this study was to determine the interrater variability and effect of state on systolic blood pressure measurements in infants </=3 years of age.

Methods: Study 1 examined interrater variability, determined by interclass correlation coefficient for 2 raters, and the effect of state on systolic blood pressure measurements in infants at 1, 2, and 3 years. Study 2 examined the variability of duplicate systolic blood pressure measurements by a single rater determined by interclass correlation coefficient and effect of state in 120 infants at 1, 2, and 3 years. Systolic blood pressure was defined as the Doppler-amplified sound corresponding to the first Korotkoff sound using a sphygmomanometer with appropriate cuff size. State was scored as follows: 1, sleeping; 2, awake and calm; 3, awake and fussy/restless; and 4, awake and vigorously crying/screaming.

Results: In study 1, the overall interclass correlation coefficient for systolic blood pressure was 0.81 and decreased when state varied between raters. When compared with a calm state 1 and/or 2 at both measurements, noncalm state 3 and/or 4 at both measurements was associated with an increase in systolic blood pressure. Although state was similar in infants born at </=36 and >36 weeks' gestational age, the former had a systolic blood pressure 13.0 +/- 14 mm Hg greater than the 50th centile for age and gender versus 2.4 +/- 12 mmHg for those >36 weeks' gestation. In study 2, the interclass correlation coefficient for repeated measurements by a single rater was 0.85, and noncalm state at both measurements was associated with an elevated systolic blood pressure.

Conclusions: Systolic blood pressure can be accurately measured in the first 3 years after birth, but state modifies systolic blood pressure and must be determined at the time of measurement. Infants born at </=36 weeks' estimated gestational age may be at risk for an elevated systolic blood pressure, but this requires additional study.