Differences between the fourth and fifth Korotkoff phases among children and adolescents

The relative importance of the fourth (K4) and fifth (K5) Korotkoff phases as the indicator of diastolic blood pressure (DBP) levels among children remains uncertain.

In a sample of 11,525 youth aged 5-17, we examined interexaminer differences in these 2 phases and the relation of theses 2 phases to adult blood pressure levels and hypertension. The longitudinal analyses were conducted among 2,156 children who were re-examined after age 25 years.

Mean (±SD) levels of DBP were 62 (±9) mm Hg (K4) and 49 (±13) mm Hg (K5). K4 showed less interobserver variability than did K5, and 7% of the children had at least 1 (of 6) K5 value of 0mm Hg. Longitudinal analyses indicated that K4 was more strongly associated with adult blood pressure levels and hypertension. In correlational analyses of subjects who were not using antihypertensive medications in adulthood (n = 1,848), K4 was more strongly associated with the adult DBP level than was K5 (r = 0.22 vs. 0.17; P < 0.01). Analyses of adult hypertension (based on high blood pressure levels or use of antihypertensive medications) indicated that the screening performance of childhood levels of K4 was similar to that of systolic blood pressure and was higher than that of K5, with areas under the receiver operator characteristic curves of 0.63 (systolic blood pressure), 0.63 (K4), and 0.57 (K5).

As compared with K5 levels among children, K4 shows less interobserver variability and is more strongly associated with adult hypertension.