OBJECTIVEThe best approach for blood pressure (BP) measurement in children remains controversial, especially on the choice of Korotkoff phase 4 (K4) vs. Korotkoff phase 5 (K5) for diastolic BP (DBP) and to compare the differences between K4 and K5 in school-aged children and their predictions to hypertension in adult.

METHODSThe "Beijing children and adolescents BP study" cohort population consisted 2505 school-aged children aged 6 to 17 at baseline survey in 1987, when datum of systolic BP (SBP), DBP measured using K4 and K5, were collected respectively. Among them, 412 individuals with 220 males and 192 females at age of 23-37 years old, were successfully followed up and invited to take part in a clinical examination including anthropometric measurements, SBP and DBP recordings, and a questionnaires in 2005. Method for the BP measurements at both baseline and followed-up was by auscultation with a standard sphygmomanometer. Child hypertension at baseline was diagnosed according to the age-specific cutoffs recommended by the World Health Organization in 1996 (WHO 1996). Adult hypertension was diagnosed according to the China Guideline for Hypertension Prevention and Control issued in 2005. Partial correlation coefficients were calculated to describe the association of K4 and K5 in childhood with SBP and DBP level in adulthood. Multivariate logistic regression analysis was conducted to examine the impact of choice of K5 and K4 as DBP in childhood on prediction to the hypertension in adulthood. Potential confounders such as gender and adult-height were controlled for.

RESULTSAt baseline, the prevalence rates of hypertension were 5.0% with DBP measured using K4, and 2.4% with DBP measured using K5, respectively. The geometric mean difference value of K4 minus K5 (K4 - K5) was (10.1 +/- 1.7 mm Hg) (1 mm Hg = 0.133 kPa) for the 2505 school-aged children, and decreased as age increased. There was no significant difference regarding the values of K4 - K5 between males and females in all age groups except for children who at pubertal stage. The distribution of K4 - K5 value across age groups was statistically significant (P < 0.001), 59.6%, 60.5%, 56.3% and 45.1% of children who aged 6-9 years, 10-12 years, 13-15 years, and 16-17 years with their K4 - K5 value over 10 mm Hg. K4 in childhood was better correlated to both SBP and DBP in adulthood than K5. In general, K4 seemed to be superior to K5 in predicting hypertension in adulthood. The odds ratios of hypertension in adulthood were 1.69 (95% CI: 1.11-2.00), 1.45 (1.05-2.02), 2.18 (1.37-3.47), and 1.66 (1.07-2.59) with each 5 mmHg increasing of K4 measured in children aged 6-9 years, 10-12 years, 13-15 years, and 16-17 years, respectively. The agreement diagnosis between child hypertension and adult hypertension was higher for childhood DBP measured using K4 (20.2%) than that using K5 (12.8%).

CONCLUSIONThere was significant difference between K4 and K5 in Chinese children and adolescents. Choice of diastolic Korotkoff blood pressure could affect DBP tracking from childhood into adulthood. K4 seemed superior to K5 when using auscultator technique to measure DBP.