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Oscillometric blood pressure by age and height for non overweight children and adolescents in Lubumbashi, Democratic Republic of Congo

  • Emmanuel Kiyana Muyumba1,
  • Dophra Ngoy Nkulu1,
  • Clarence Kaut Mukeng2,
  • Jacques Mbaz Musung3,
  • Placide Kambola Kakoma1,
  • Christian Ngama Kakisingi1,
  • Oscar Numbi Luboya4, 5, 6,
  • Françoise Kaj Malonga5,
  • Justin Kalungwe Kizonde7,
  • Olivier Mukuku4, 6Email authorView ORCID ID profile and
  • Weili Yan8
BMC Cardiovascular DisordersBMC series – open, inclusive and trusted201818:9

https://doi.org/10.1186/s12872-018-0741-4

Received: 23 August 2016

Accepted: 2 January 2018

Published: 19 January 2018

Abstract

Background

The diagnosis of hypertension in children is complex because based on normative values by sex, age and height, and these values vary depending on the environment. Available BP references used, because of the absence of local data, do not correspond to our pediatric population. Accordingly, our study aimed to provide the BP threshold for children and adolescents in Lubumbashi (DRC) and to compare them with German (KIGGS study), Polish (OLAF study) and Chinese (CHNS study) references.

Methods

We conducted a cross-sectional study among 7523 school-children aged 3 to 17 years. The standardized BP measurements were obtained using a validated oscillometric device (Datascope Accutor Plus). After excluding overweight and obese subjects according to the IOTF definition (n = 640), gender-specific SBP and DBP percentiles, which simultaneously accounted for age and height by using an extension of the LMS method, namely GAMLSS, were tabulated.

Results

The 50th, 90th and 95th percentiles of SBP and DBP for 3373 boys and 3510 girls were tabulated simultaneously by age and height (5th, 25th, 50th, 75th and 95th height percentile).

Before 13 years the 50th and 90th percentiles of SBP for boys were higher compared with those of KIGGS and OLAF, and after they became lower: the difference for adolescents aged 17 years was respectively 8 mmHg (KIGGS) and 4 mmHg (OLAF). Concerning girls, the SBP 50th percentile was close to that of OLAF and KIGGS studies with differences that did not exceed 3 mmHg; whereas the 90th percentile of girls at different ages was high. Our oscillometric 50th and 90th percentiles of SBP and DBP were very high compared to referential ausculatory percentiles of the CHNS study respectively for boys from 8 to 14 mmHg and 7 to 13 mmHg; and for girls from 10 to 16 mmHg and 11 to 16 mmHg.

Conclusions

The proposed BP thresholds percentiles enable early detection and treatment of children and adolescents with high BP and develop a local program of health promotion in schools and family.

Keywords

Blood pressureChildrenAdolescentsLubumbashiPercentile tablesGMLSSLMS

Background

Several publications have shown the importance of measuring the blood pressure (BP) and hypertension in childhood and adolescence [14]. In children and adolescents, high BP values are associated with left ventricular hypertrophy [5], increase in thickness intima-media of arteries [6] and they are predictive of hypertension in adulthood [7].

Pediatricians have at their disposal BP references tables, which determine whether BP is normal or if it is a threshold that requires the application of the assessment, prevention or treatment. BP references are based on sex, age and height, but also on study populations characteristics such as ethnicity or nationality, including the type of device used to measure BP [1, 2, 8, 9].

Obesity has become epidemic in the world in adults as well as in children and adolescents [10, 11]. Adiposity in childhood, as measured by body mass index (BMI) [12] is an important predictor of elevated BP. In a study among 197,191 children aged 7–17 years obtained from a Chinese national survey in 2010, Dong et al. [13] noted that overweight and obese children have a significantly higher risk of high BP than non-overweight children.

BP references or standards are not available for Congolese children in the Democratic Republic of Congo (DRC) but there are many others [1, 2, 1416] that do not correspond to our pediatric population.

The objectives of our study were to establish the BP threshold percentiles of non-overweight children and adolescents in Lubumbashi (DRC) and compare them with German, Polish and Chinese BP references.

Methods

Design, participants and setting of the study

The study took place in Lubumbashi (Province of Haut-Katanga) the second city of the DRC by its economic, political, social and cultural importance. The studied population was composed of school children aged 3 to 17 years, enrolled in pre-primary, primary and secondary schools during the school-years 2013–2014, 2014–2015 and 2015–2016.

A cross-sectional study was conducted on a representative sample of these pupils, who were recruited in randomly selected clusters using two-stage sampling. The first cluster was comprised of selected schools from all private and public schools of Lubumbashi. The second cluster was comprised of randomly selected classes within each of the selected schools. All pupils in the selected classes were invited to join the study. Sampling was stratified by township.

For a strate (township), the equation allowing the calculation of the sample was the following:

\( n={z}^2\frac{p\left(1-p\right)}{e^2} \)

In which: - z is the level of confidence (= 95%).

- p is the initial level of the school attendance rate (= 50%).

- e is the error margin (= 0.05%).

The size calculated in this way had been adjusted according to the effect of the sampling plan (= 1.5%), the number of estimations by age group and by sex (= 3%) and this was reported to the expected number of non-answers (= 20%). The number thus obtained was multiplied by the number of the strate (township) of the city of Lubumbashi (for details, please consult website www.unilu.ac.cd/wp-content/uploads/2016/07/Seuils1.pdf).

Informed written consent was obtained from parents or guardians. The approval to conduct the study and authorizations were obtained from the Medical Ethic Committee of the University of Lubumbashi (UNILU/CEM/027/2013–27 september 2013), the Provincial Ministry of Education, Scientific Research, Transport and Energy of Katanga (N° 10.5/0209/CAB/MIN.PROV/ED.R.TE/KAT/2014–11 march 2014) and the authorities of the selected schools.

Data were collected by trained medical staff. The study team received refresher training at the beginning of each data collection phase.

BP measurement

BP was measured by using a Datascope Accutorr Plus (Datascope Corporation, USA). The appropriate cuff size (bladder width at least 40% of arm circumference and length to cover 80–100% of arm circumference) was determined by measuring the mid-upper arm circumference.

BP measurements were performed at least 30 min after exercise or the last meal, in a subject at rest 5 min before setting, in a seated position with arm and back supported, feet resting on the floor and legs uncrossed. The cuff was applied to the right arm, at the heart level, then wrapped in a sealing which did not allow two fingers to be inserted under it. The lower edge of the cuff was placed 2 cm from the cubital fossa. Three readings were obtained at a 1 min intervals on the same day and the mean of the second and third readings was used for analysis.

Anthropometric measurements

Body weight was measured in duplicate with the participant wearing light underwear, barefoot, standing on a digital scale. Body weight was recorded nearest 0.1 kg. Body height recorded nearest 0.1 cm was measured in duplicate. Each participant was in standing upright position, barefoot with shoulders and hips perpendicular at the central axis, heels against the step, knees together, arms relaxed along the body and head straight. Special attention was given to children (under 6 years) using a second investigator to block the movement of the knees. The mean of the two measurements of weight and height and were selected for statistical analysis.

BMI was calculated as weight (in kilograms) divided by the square of height (in meters). The terms overweight and obese were defined according to the International Obesity Task Force (IOTF) definition [17].

Inclusion and exclusion criteria for the sample on which the percentiles are based

Of 8371 participants consented, we excluded 1488: 795 children were younger than 3 years (n = 55) or over 17 years (n = 740), 53 had outlying or missing data (date of birth, BP, weight, height) and 640 were recorded overweight (n = 548) or obese (n = 92). No child had been reported to have a chronic disease likely to influence weight or blood pressure and also no child was taking a medicine having an influence on the blood pressure (Additional file 1).

Statistical analysis

All statistical analyses were performed using SPSS version 22.0 (SPSS Inc., Chicago, IL, USA) and the free statistical software R 3.1.2 (2014–10-31) (http://www.cran.r-project.org).

Thresholds of BP by gender were constructed by age and height simultaneously using an extension of the LMS method [18], namely generalized additive models for location scale and shape (GAMLSS) with the Box-Cox power exponential (BCPE) and Box-Cox-Cole-Green (BCCG) distributions families, fitted with GAMLSS 4.3–1 in the free statistical software R 3.1.2 (2014–10-31). In GAMLSS [18, 19], four parameters (μ, σ, ν, τ) were used to define the location, scale and shape of the BP distribution with age and height. To obtain the optimal models by minimizing the Schwarz Bayesian Criterion [20], linear and additive effect of age and height on systolic blood pressure (SBP) and diastolic blood pressure (DBP) were modeled simultaneously. The threshold values of the 50th, 90th and 95th percentiles of SBP and DBP were calculated by age and height (exact heights according to the 5th, 25th, 50th, 75th and 95th percentiles) for boys and girls separately.

Different percentiles of SBP and DBP (50th and 90th percentiles) for boys and girls, were compared with references percentiles of the German Health Interview and Examination Survey for Children and Adolescents (KIGGS) [14], the Elaboration of the Ranks of Reference Arterial Blood Pressure for the Population of Children and Adolescents in Poland (OLAF) [15] and the Chinese reference that used data from the China Health and Nutrition Survey (CHNS) [16]. This comparison was made for the different ages in relation to the target population of these studies (3–17 years for KIGGS and 7–17 years for OLAF and CHNS).

Results

Of the 11,283 pupils selected and invited to take part in the study, 8371 children and adolescents consented and were enrolled for a global participation rate of 74.2%. Data were collected three times (according to the school calendar in the DRC) from March 2014 to December 2015; in 66 schools. The reference population of non-overweight children and adolescents aged 3 to 17 years consisted of 3373 boys and 3510 girls.

Table 1 summarized the baseline characteristics of 6883 non-overweight children and adolescents. The mean of SBP and DBP increased with age in both sexes. The mean of the first BP (both systolic and diastolic) was the highest and the mean of the third BP was the lowest in the series of three measures in both sexes and in all age groups. The mean of the first and second BP was higher: 0.8 to 1.4 mmHg SBP and 0.9 to 2.0 mmHg DBP, in comparison with the average of the second and third BP (Table 1).
Table 1

Baseline characteristics of children and adolescents of normal weight aged 3 to 17 years in Lubumbashi, DRC

 

Age, year

3–6

7–10

11–13

14–17

n, included (% 3373 boys, 3510 girls)

 Boys

480 (14.2)

1161 (34.4)

995 (29.5)

737 (21.9)

 Girls

393 (11.2)

1133 (32.3)

1014 (28.9)

970 (27.6)

Weight, mean (SD), kg

 Boys

18.7 (3.1)

29.7 (4.8)

35.9 (6.5)

50.9 (8.8)

 Girls

18.6 (3.5)

27.1 (5.5)

39.0 (7.5)

50.4 (6.5)

Height, median (SD), cm

 Boys

111.1 (8.8)

130.5 (9.0)

142.3 (9.4)

162.3 (10.2)

 Girls

111.3 (10.2)

131.2 (9.9)

148.0 (9.6)

159.0 (7.4)

IMC, mean (SD) kg / m2

 Boys

15.1 (1.2)

15.6 (1.4)

16.9 (1.7)

19.2 (2.1)

 Girls

14.9 (1.1)

15.6 (1.5)

17.7 (2.1)

19.9 (2.1)

First SBP, mean (SD), mmHg

 Boys

101.7 (11.0)

104.6 (10.6)

109.2 (10.3)

118.0 (12.4)

 Girls

102.0 (11.1)

106.7 (10.7)

112.6 (11.9)

116.9 (11.3)

Second SBP, mean (SD), mmHg

 Boys

100.7 (11.0)

103.4 (10.7)

107.7 (10.5)

116.7 (12.3)

 Girls

100.3 (10.6)

105.5 (10.7)

111.2 (11.1)

115.5 (10.8)

Third SBP, mean (SD), mmHg

 Boys

99.7 (10.9)

102.4 (10.0)

106.8 (9.9)

115.3 (11.9)

 Girls

99.4 (10.3)

104.1 (10.2)

110.1 (10.8)

114.1 (10.6)

Mean of first and second SBP, mean (SD), mmHg

 Boys

101.2 (10.4)

104.0 (9.9)

108.5 (9.7)

117.4 (11.7)

 Girls

101.2 (10.2)

106.1 (10.1)

111.9 (10.8)

116.2 (10.5)

Mean of second and third SBP, mean (SD), mmHg

 Boys

100.2 (10.4)

102.9 (9.8)

107.2 (9.7)

116.0 (11.6)

 Girls

99.8 (9.8)

104.8 (10.0)

110.6 (10.4)

114.8 (10.2)

First DBP, mean (SD), mmHg

 Boys

62.8 (9.6)

65.1 (9.1)

67.1 (7.9)

69.4 (9.0)

 Girls

63.5 (9.5)

66.2 (9.2)

68.2 (8.8)

70.5 (8.5)

Second SBP, mean (SD), mmHg

 Boys

61.8 (8.5)

63.4 (9.0)

65.4 (8.4)

67.5 (8.8)

 Girls

61.9 (9.6)

65.0 (8.7)

66.4 (8.7)

68.1 (8.5)

Third DBP, mean (SD), mmHg

 Boys

61.0 (8.9)

62.2 (8.9)

64.2 (8.1)

67.0 (9.2)

 Girls

60.9 (8.8)

63.7 (8.9)

65.2 (9.0)

67.0 (8.5)

Mean of first and second DBP, mean (SD), mmHg

 Boys

62.3 (8.0)

64.3 (8.0)

66.3 (7.2)

68.4 (7.9)

 Girls

62.7 (8.5)

65.8 (7.8)

67.3 (7.7)

69.3 (7.6)

Mean of second and third DBP, mean (SD), mmHg

 Boys

61.4 (7.7)

62.8 (7.9)

64.8 (7.4)

67.3 (8.1)

 Girls

61.4 (8.1)

64.3 (7.8)

65.8 (7.9)

67.6 (7.6)

SD standard deviation, BMI body mass index, SBP systolic blood pressure, DBP diastolic blood pressure

Among the best fitted models for the 4 parameters of distribution of SBP and DBP, the Box-Cox and Cole Green (BCCG) was shown as the best fit model of SBP for both genders and DBP for girls; while the Box-Cox Power Exponential (BCPE) was for the boys’ DBP.

The thresholds 50th, 90th and 95th percentiles of SBP and DBP were tabulated simultaneously by age and exact height (5th, 25th, 50th, 75th and 95th height percentile) respectively for boys and girls and are shown in Tables 2 (for boys) and 3 (for girls). The BP increased both in relation to age and height in both sexes. The median SBP and DBP were higher (about 2 mmHg) in girls up to the age 14 years, after this age they were almost similar in both sexes. As an illustration, in adolescents aged 17 years with a median height (167 cm for boys and 162 cm for girls), the median percentiles of SBP and DBP were similar, respectively 115 mmHg and 68 mmHg. The 95 percentile used to define hypertension in children and adolescents had varied between the 5th and 95th percentile height (SBP in boys: 4–7 mmHg and in girls: 5–8 mmHg; DBP in boys: 1–3 mmHg and in girls: 1–2 mmHg).
Table 2

Age-height-specific thresholds: 50th, 90th and 95th percentiles of SBP and DBP values for boys aged 3–17 years

Age, year

Height, cm

Height percentile

SBP, mmHg

DBP, mmHg

S*

50th percentile (median)

90th percentile

95th percentile

S*

50th percentile (median)

90th percentile

95th percentile

3

87

5th

0.0983

91

103

107

0.0712

59

68

71

 

94

25th

0.0974

92

105

109

0.0678

59

69

72

 

97

50th

0.0970

93

105

110

0.0667

59

69

72

 

101

75th

0.0964

94

106

111

0.0647

60

69

72

 

107

95th

0.0956

95

108

112

0.0623

60

70

72

4

95

5th

0.0972

93

106

110

0.0674

60

69

72

 

99

25th

0.0967

94

107

111

0.0655

60

70

72

 

103

50th

0.0961

95

108

112

0.0638

60

70

73

 

108

75th

0.0955

96

108

113

0.0619

60

70

73

 

112

95th

0.0949

97

110

114

0.0599

61

70

73

5

101

5th

0.0964

95

108

112

0.0648

60

70

73

 

106

25th

0.0957

96

109

113

0.0626

61

70

73

 

109

50th

0.0953

97

109

114

0.0612

61

71

73

 

114

75th

0.0946

98

111

115

0.0592

61

71

74

 

122

95th

0.0936

99

112

116

0.0561

61

71

74

6

105

5th

0.0959

96

109

113

0.0630

61

71

73

 

112

25th

0.0949

98

111

115

0.0601

61

71

74

 

116

50th

0.0944

98

112

116

0.0584

61

71

74

 

120

75th

0.0938

99

113

117

0.0567

62

72

74

 

127

95th

0.0929

101

114

118

0.0542

62

72

75

7

112

5th

0.0949

98

111

116

0.0598

62

71

74

 

118

25th

0.0941

99

113

117

0.0576

62

72

75

 

123

50th

0.0935

100

114

118

0.0557

62

72

75

 

126

75th

0.0930

101

114

119

0.0544

62

72

75

 

137

95th

0.0916

103

117

121

0.0506

63

73

76

8

112

5th

0.0949

99

112

116

0.0599

62

72

75

 

123

25th

0.0934

101

114

119

0.0556

62

72

75

 

128

50th

0.0928

102

115

120

0.0538

63

73

76

 

132

75th

0.0922

103

116

121

0.0523

63

73

76

 

140

95th

0.0912

105

118

122

0.0495

63

74

77

9

122

5th

0.0936

101

115

119

0.0562

63

73

76

 

127

25th

0.0930

102

116

120

0.0543

63

73

76

 

132

50th

0.0923

103

117

121

0.0525

63

73

76

 

137

75th

0.0917

104

118

122

0.0507

63

74

77

 

145

95th

0.0906

106

120

124

0.0479

64

74

77

10

123

5th

0.0934

102

115

120

0.0556

63

73

76

 

131

25th

0.0924

104

117

121

0.0527

64

74

77

 

136

50th

0.0917

105

118

123

0.0509

64

74

77

 

141

75th

0.0910

106

119

124

0.0491

64

74

77

 

149

95th

0.0901

108

121

125

0.0466

64

75

78

11

129

5th

0.0927

104

117

122

0.0536

64

74

77

 

136

25th

0.0917

105

119

123

0.0508

64

74

77

 

142

50th

0.0910

107

120

124

0.0489

64

75

78

 

147

75th

0.0903

108

121

126

0.0471

65

75

78

 

156

95th

0.0892

110

123

128

0.0443

65

76

79

12

132

5th

0.0922

105

119

123

0.0522

64

74

77

 

140

25th

0.0912

107

120

125

0.0495

65

75

78

 

145

50th

0.0906

108

121

126

0.0479

65

75

78

 

151

75th

0.0898

109

123

127

0.0460

65

76

79

 

161

95th

0.0886

111

125

129

0.0430

66

76

79

13

133

5th

0.0921

106

119

124

0.0519

65

75

78

 

143

25th

0.0909

108

121

126

0.0487

65

75

78

 

150

50th

0.0900

109

123

127

0.0464

65

76

79

 

157

75th

0.0890

111

125

129

0.0440

66

76

79

 

164

95th

0.0882

112

126

131

0.0420

66

77

80

14

139

5th

0.0914

108

121

126

0.0499

65

75

78

 

149

25th

0.0901

110

123

128

0.0466

66

76

79

 

157

50th

0.0891

111

125

130

0.0442

66

77

80

 

164

75th

0.0883

113

127

131

0.0422

66

77

80

 

172

95th

0.0872

115

128

133

0.0398

67

78

81

15

145

5th

0.0906

109

123

128

0.0479

66

76

79

 

157

25th

0.0891

112

126

130

0.0442

67

77

80

 

162

50th

0.0884

113

127

131

0.0425

67

77

81

 

168

75th

0.0876

114

128

133

0.0408

67

78

81

 

177

95th

0.0866

116

130

135

0.0385

67

78

82

16

153

5th

0.0896

112

126

130

0.0453

67

77

80

 

161

25th

0.0886

113

127

132

0.0430

67

78

81

 

168

50th

0.0877

115

129

133

0.0410

67

78

81

 

172

75th

0.0871

116

130

134

0.0397

68

78

82

 

179

95th

0.0864

117

131

136

0.0380

68

79

82

17

153

5th

0.0895

112

126

131

0.0452

67

77

81

 

165

25th

0.0881

115

129

133

0.0419

68

78

81

 

167

50th

0.0878

115

129

134

0.0411

68

78

82

 

173

75th

0.0871

116

130

135

0.0395

68

79

82

 

180

95th

0.0862

118

132

136

0.0377

68

79

82

SBP systolic blood pressure, DBP diastolic blood pressure

S *, coefficient of variation of blood pressure

Table 3

Age-height-specific thresholds: 50th, 90th and 95th percentiles of SBP and DBP values for girls aged 3–17 years

Age, year

Height, cm

Height percentile

SBP, mmHg

DBP, mmHg

S *

50th percentile (median)

90th percentile

95th percentile

S *

50th percentile (median)

90th percentile

95th percentile

3

88

5th

0.0994

93

106

109

0.1313

60

70

73

92

25th

0.0996

94

107

110

0.1313

60

70

74

99

50th

0.0998

95

108

112

0.1313

60

71

74

103

75th

0.1000

96

109

113

0.1313

60

71

74

109

95th

0.1002

97

110

114

0.1313

61

71

75

4

95

5th

0.0984

95

108

111

0.1298

60

71

74

98

25th

0.0985

96

108

112

0.1298

61

71

74

102

50th

0.0987

97

109

113

0.1298

61

71

74

108

75th

0.0989

98

111

114

0.1298

61

72

75

121

95th

0.0993

100

113

117

0.1298

62

72

76

5

98

5th

0.0973

96

109

113

0.1283

61

71

74

105

25th

0.0975

98

110

114

0.1283

61

72

75

110

50th

0.0977

98

111

115

0.1283

61

72

75

115

75th

0.0979

99

113

117

0.1283

62

72

75

122

95th

0.0981

101

114

118

0.1283

62

73

76

6

105

5th

0.0963

98

111

115

0.1269

62

72

75

113

25th

0.0966

100

113

117

0.1269

62

72

76

117

50th

0.0967

100

114

118

0.1269

62

73

76

123

75th

0.0969

101

115

119

0.1269

62

73

76

131

95th

0.0972

103

117

121

0.1269

63

73

77

7

110

5th

0.0953

100

113

116

0.1254

62

73

76

118

25th

0.0955

101

114

118

0.1254

62

73

76

123

50th

0.0957

102

116

120

0.1254

63

73

76

128

75th

0.0959

103

116

121

0.1254

63

73

77

134

95th

0.0961

104

118

122

0.1254

63

74

77

8

117

5th

0.0943

102

115

118

0.1240

63

73

76

123

25th

0.0945

103

116

120

0.1240

63

74

77

128

50th

0.0947

104

117

121

0.1240

63

74

77

133

75th

0.0948

104

118

122

0.1240

63

74

77

142

95th

0.0952

106

120

124

0.1240

64

75

78

9

121

5th

0.0932

103

116

120

0.1226

63

74

77

129

25th

0.0935

104

118

122

0.1226

64

74

77

133

50th

0.0937

105

119

123

0.1226

64

74

77

138

75th

0.0938

106

120

124

0.1226

64

75

78

149

95th

0.0942

108

122

127

0.1226

65

75

78

10

126

5th

0.0922

104

118

122

0.1212

64

74

77

133

25th

0.0925

106

119

123

0.1212

64

75

78

137

50th

0.0926

107

120

124

0.1212

64

75

78

143

75th

0.0928

108

121

126

0.1212

65

75

78

152

95th

0.0931

109

123

128

0.1212

65

76

79

11

127

5th

0.0911

105

118

122

0.1198

64

75

78

138

25th

0.0915

107

121

125

0.1198

65

75

78

145

50th

0.0917

108

122

127

0.1198

65

76

79

150

75th

0.0919

110

123

128

0.1198

65

76

79

157

95th

0.0921

111

125

130

0.1198

66

76

79

12

132

5th

0.0901

107

120

124

0.1184

65

75

78

142

25th

0.0905

109

122

126

0.1184

65

76

79

149

50th

0.0907

110

124

128

0.1184

66

76

79

154

75th

0.0908

111

125

129

0.1184

66

76

79

161

95th

0.0911

112

126

131

0.1184

66

77

80

13

139

5th

0.0892

109

122

126

0.1171

65

76

79

148

25th

0.0895

110

124

128

0.1171

66

76

79

154

50th

0.0897

111

125

130

0.1171

66

77

80

159

75th

0.0899

112

126

131

0.1171

66

77

80

166

95th

0.0901

114

128

133

0.1171

67

77

80

14

143

5th

0.0882

110

123

128

0.1157

66

76

79

153

25th

0.0885

112

125

130

0.1157

66

77

80

157

50th

0.0887

113

126

131

0.1157

67

77

80

162

75th

0.0888

113

128

132

0.1157

67

77

80

168

95th

0.0890

115

129

134

0.1157

67

78

81

15

147

5th

0.0872

111

125

129

0.1144

67

77

80

154

25th

0.0874

113

126

131

0.1144

67

77

80

159

50th

0.0876

113

127

132

0.1144

67

77

80

164

75th

0.0878

114

128

133

0.1144

67

78

81

171

95th

0.0880

116

130

135

0.1144

68

78

81

16

148

5th

0.0862

112

125

130

0.1131

67

77

80

156

25th

0.0864

114

127

131

0.1131

67

77

80

161

50th

0.0865

114

128

133

0.1131

68

78

81

164

75th

0.0867

115

129

133

0.1131

68

78

81

174

95th

0.0870

117

131

136

0.1131

68

78

81

17

150

5th

0.0851

113

126

131

0.1118

67

77

80

156

25th

0.0853

114

128

132

0.1118

68

78

81

162

50th

0.0855

115

129

133

0.1118

68

78

81

166

75th

0.0856

116

130

134

0.1118

68

78

81

173

95th

0.0858

117

131

136

0.1118

68

79

82

SBP systolic blood pressure, DBP diastolic blood pressure

S *, coefficient of variation of blood pressure

For adolescents boys aged 11–17 years and girls aged 10–17 years, the 90th SBP percentile for the median height was respectively 120–132 mmHg and 120–131 mmHg.

In the case of boys aged 5–12 years, the 50th SBP percentile of our oscillometric threshold was similar to the corresponding percentile of German oscillometric reference (KIGGS study), whereas compared with the Polish oscillometric reference (OLAF study) the difference were less than 2 mmHg in age 7, 8 and 13, 14 years (Fig. 1). The 50th percentile of SBP of the KIGGS study was higher for boys >14 years (8 mmHg for adolescents aged 17 years). With regard to girls, the 50th SBP percentile of our study was close to the corresponding percentile of the KIGGS and OLAF studies: the differences did not exceed 2 mmHg, except among girls aged 9 and 10 years (for OLAF study) in which the difference was greater than 3 mmHg (Fig. 2).
Fig. 1

The 50th and 90th percentiles of SBP for the median height for our study (NOTRE) compared with the German (KIGGS), Polish (OLAF) and Chinese (CHNS) boys

Fig. 2

The 50th and 90th percentiles of SBP for the median height for our study (NOTRE) compared with the German (KIGGS), Polish (OLAF) and Chinese (CHNS) girls

For boys <13 years the 90th SBP percentile was higher from 1 to 4 mmHg in comparison to KIGGS and OLAF percentiles. After, it became progressively lower: for adolescents aged 17 the difference was 8 mmHg with the KIGGS study and 4 mmHg with the OLAF study (Fig. 1). In the case of girls, our 90th SBP percentile was consistently higher compared to KIGGS and OLAF percentiles (Fig. 2).

The 50th and 90th DBP percentiles of the KIGGS boys (Fig. 3) were higher at all ages (among adolescents aged 17 years the difference was 4 mmHg). In case of the girls age range 7–17 years, the 50th and 90th DBP percentiles of OLAF study were higher when compared with our corresponding percentile.
Fig. 3

The 50th and 90th percentiles of DBP for the median height for our study (NOTRE) compared with the German (KIGGS), Polish (OLAF) and Chinese (CHNS) boys

In comparing the 50th and 90th SBP percentiles for median height for our oscillometric values to the Chinese ausculatory referential (CHNS) values, the 50th and 90th percentiles were consistently very higher among the children and adolescents of the same age: the difference was 8 to 14 mmHg and 7 to 13 mmHg for boys (Fig. 1); and 10 to 16 mmHg and 11–16 mmHg for girls (Fig. 2). The 50th and 90th DBP percentiles for boys (Fig. 3) and girls (Fig. 4) of our study were higher before age 11 years in comparison to the CHNS study; and in the age range 11–17 years, the difference were relatively minor (not exceeding 2 mmHg).
Fig. 4

The 50th and 90th percentiles of DBP for the median height for our study (NOTRE) compared with the German (KIGGS), Polish (OLAF) and Chinese (CHNS) girls

Discussion

This study presents the first BP threshold percentiles for children and adolescents of normal weight aged 3–17 years in Lubumbashi (DRC), computed by age and height simultaneously, by using an improved statistical method named GAMLSS provided in the package of R software [14, 16, 19]. The BP percentiles were established on the basis of oscillometric measurements of the BP with a device clinically validated in children: the Datascope Accutorr Plus [21]. This device has also been used in several large studies related to BP in children and adolescents worldwide [14, 15, 22]. In addition, the oscillometric BP measurement is increasingly used in pediatric clinical practice.

We have not included overweight or obese subjectsin our study. Using a sample of normal weight to develop percentile allows our proposed BP thresholds to be more sensitive to the identification of children and adolescents with high BP because we avoided certain risk factors associated with the BP as being overweight or obese [10, 13]. Sorof et al. [23] found a strong correlation between the BP and overweight and obesity.

Our mean SBP (for girls) and DBP (for boys and girls) were higher compared to those observed by Kulaga et al. [15]. Compared to the mean of the first and second BP (both systolic and diastolic) values were higher than those of children and adolescents in the KIGGS study [14].

The height is a key covariate associated with BP levels [1]. Indeed, not taking into account the height in establishing the BP references could lead to an inaccurate assessment of the BP in pediatric practice particularly for children who are very small (5th percentile) or very tall (95th percentile). Our BP thresholds do not require the use of height reference tables because it is presented in centimeters. In addition, this presentation of exact height by value (in centimeters) in different categories of height percentile is proposed to the allow evaluation of the children and adolescents BP more convenient and accurate.

We proposed the 90th and 95th BP percentiles to allow the detection of prehypertension and hypertension in children and adolescents. These cut-off values for prehypertension and hypertension respectively, were used according to the criteria’s definition of the Fourth Report on the Diagnosis, Evaluation and Treatment of High Blood Pressure in Children and Adolescents [1] and to the recommendations of the European Society of Hypertension on the Management of High Blood Pressure in Children and Adolescents [2]. Because of the large amount of data available, the Task Force for Blood Pressure in Children [1] is still the study of reference. We have not presented the 99th BP percentile. Indeed, a child or adolescent with BP value that defines hypertension (≥ 95th percentile compared to reference tables) will not be diagnosed by this measure alone as being hypertensive but other additional BP measures are recommended on different occasions [1, 2]. Owing to cultural and ethnic diversity of the peoples of the DRC, our results cannot extrapolate to the entire nation.

The 90th SBP percentile for the median height of adolescents for boys aged 11–17 years and girls aged 10–17 years, respectively of 120–132 mmHg and 120–131 mmHg, was equal to or higher than the threshold 120 mmHg for the identification of prehypertension as recommended by the fourth report of the National High Blood Pressure Education Program (NHBPEP) Working Group on High Blood Pressure in Children and Adolescents [1], the European Society of Hypertension [2] and the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and treatment of High Blood Pressure (JNC VII) [24]. This observation may indicate the need for careful consideration of changes to the definition of prehypertension in the case of adolescent. The fact that the BP of Congolese children of Lubumbashi is so high at the beginning of adolescence, could be justified by several observations showing that hypertension in black subjects occurs at the early age [25, 26]. In addition, the 90th BP percentile for adolescents aged 17 years (in both sexes) was 130 mmHg, which is equal to the recommended optimal SBP for adult to define metabolic syndrome [27]. Our results are almost similar to those reported by Kulaga et al. [15] and Neuhauser et al. [14]. For the first authors, the 90th SBP percentile for adolescents age range 13–17 years (boys) and 12–17 years (girls) was respectively 122–133 mmHg and 120–126 mmHg. While for the second author, adolescents aged 12 to 17 (both boys and girls) had their 90th SBP percentile respectively 120–137 mmHg and 122–126 mmHg. In the CHNS study [16], only adolescent boys aged 15 to 17 had the 90th percentile of SBP and DBP at 122 and 80 mmHg close to the threshold of 120/80 mmHg for the identification of prehypertension. In this study the BP values are examined by mercury sphygmomanometer.

We compared our percentiles with the KIGGS [14], OLAF [15] and CHNS [16] studies because they are all tools that aim to solve the same problem: screening and detection of elevated BP in children. In addition, the construction of the BP percentiles was based on the normal weight subjects and developed simultaneously by age and height.

Several reasons could explain the differences with each study. In particular, the devices used for the BP measurement (auscultatory, oscillometric). It is known as oscillometric devices provide high values of the BP compared to mercury sphygmomanometer [1]. The Datascope Accutor Plus had passed the standards of the Association for the Advancement of Medical Instrumentation [28] and the British Hypertension Society [29] for adults and had been validated in children aged 5 to 15 years compared to the mercury sphygmomanometer as required of the International Protocol of the European Society of Hypertension (ESH-IP) [30]. In the validation study in children [21], measures of the Datascope Accutor Plus were close to the sphygmomanometer measurements: the mean (SD) of the differences was for PAS values (oscillometric least auscultation) of - 0.9 (4.33) mmHg and DBP - 1.2 (6.48) mm Hg. The number of the BP measurements used for the establishment of the BP percentiles. As for Kulaga et al. [15], our study used the mean of the last two measures (of the three) BP for statistical analysis because the first one are often high [31, 32]. The statistical method used for the BP percentiles construction. The GAMLSS method was used in our study and those of Neuhauser et al. [14] et Yan et al. [16]; while Kulaga et al. [15] had used the polynomial regression. Another possible reason is the lack of a uniform definition for overweight and obesity for the non-inclusion of this group of children and adolescents in the study of normal weight population. Neuhauser et al. [14] had used the 90th percentile of the BMI of the German reference and Yan et al. [16] were based on the reference BMI of Chinese children and adolescents. Like in the OLAF study [15], we used the definition IOTF [17], because we have not BMI reference for children in our country and it is consistent with the levels of overweight and obesity in childhood and adolescence (2–18 years), with the definition of overweight (≥ 25 kg / m2) and obesity (≥ 30 kg / m2) in adults. We also took into account the recommendations of the European Childhood Obesity Group [33]: which suggest the use of the definition of the IOTF or the WHO definition in epidemiological studies. Ethnic, racial, geographic differences may also explain the variability of the BP in the populations studied [25, 34].

A possible limitation of our study is the selection bias. Owing to the lack of official documents, we used a reported age declaration by parents or guardians. Another limitation was related to a lack external validation made to assess the performance of our proposed BP thresholds.

Conclusion

We established, for the first time, the thresholds percentiles (50, 90 and 95) of the BP for specific age and height of children and adolescents aged 3 to 17 years in Lubumbashi (DRC) for the use in pediatric clinical practice. Early identification of prehypertension and hypertension in children and adolescents leads to early action to the support and possibly the prevention of late morbidity and mortality. The BP thresholds percentiles proposed by the current study enable to develop a local program of health promotion in schools and family.

We observed that the 90th percentile of SBP in early adolescence is high and this corresponds to the prehypertension thresholds requiring further studies.

Abbreviations

BCCE: 

Box-Cox and Cole Green

BCPE: 

Box-Cox power exponential

BMI: 

Body mass index

BP: 

Blood pressure

CHNS: 

China Health and Nutrition Survey

DBP: 

Diastolic blood pressure

DRC: 

Democratic Republic of Congo

ESH: 

European Society of Hypertension

GMLSS: 

Generalized Additive Models for Location, Shape, and Scale

IOTF: 

International Obesity Task Force

IP-ESH: 

International Protocol of the European Society of Hypertension

JNC VII: 

Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and treatment of High Blood Pressure

KIGGS: 

German Health Interview and Examination Survey for Children and adolescents

LMS: 

Lambda Mu Sigma

NHBPEP: 

National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents

OLAF: 

Elaboration of the reference range of arterial blood pressure for the population of children and adolescents in Poland

SBP: 

Systolic blood pressure

SD: 

Standard deviation

SPSS: 

Statistical Package for Social Sciences

Declarations

Acknowledgements

We thank Dr. Robert A. Rigby for his kind help in modeling blood pressure using GAMLSS program.

Funding

We have not received any funding. The study was conducted on our own.

Availability of data and materials

Raw data and other relevant materials are available upon request from the corresponding author (OM).

Authors’ contributions

EKM, CKM, JMM, PKK, CNK, OM, DNN and WY carried out the conceptualization, design, data collection and analysis for the study. ONL, JKK, FKM and OM contributed to the interpretation of the findings and the drafting of the article. EKM and OM wrote the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

The approval to conduct the study and authorizations were obtained from the Medical Ethic Committee of the University of Lubumbashi (UNILU/CEM/027/2013–27 september 2013), the Provincial Ministry of Education, Scientific Research, Transport and Energy of Katanga (N° 10.5/0209/CAB/MIN.PROV/ED.R.TE/KAT/2014–11 march 2014) and the authorities of the selected schools. Data was used with high confidentiality and no names were recorded. The informed written consent to participate was obtained from the parent/guardians of the child or adolescent.

Consent for publication

The informed written consent to participate and for the publication of individual clinical details was obtained from the parent/guardians of the child or adolescent.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

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Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
Department of Internal Medicine, Sendwe Hospital, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(2)
Department of Public Health, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(3)
Department of Internal Medicine, University Clinic, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(4)
Department of Pediatrics, University Clinic, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(5)
School of Public Health, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(6)
Department of Research, Higher Institute of Medical Techniques, Lubumbashi, Democratic Republic of Congo
(7)
Department of Gynecology, Clinical University of Lubumbashi, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
(8)
Department of Clinical Epidemiology, Children’s Hospital of Fudan University, Shanghai, China

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