adekanmbi a.f,* diagnosis of childhood hypertension: is blood pressure adejumo a.o ... of...

IntroductionHypertension is reported to be established in

1 childhood and studies have shown that hypertension can be diagnosed from third year of life. Childhood hypertension is however under diagnosed because of the associated cumbersomeness of age, gender and height percentile charts proposed by the Fourth Report on the diagnosis, evaluation and treatment of high blood pressure in

2children and adolescents. The use of mathematical formula, gender based figures,

gender and height based diagnosis and gender based cut offs have been suggested by some

3-7authors. Although these techniques have various limitations. The use of blood pressure to height ratio was proposed in 2011 by Lu et

8 9al and Guo et al. In spite of the high sensitivities of this method which ranged between 96.4% - 100% in boys and 95% - 99.2% in girls irrespective of age, the gold standard is still that recommended by the task

10-12force. This method has an advantage of being cheap and can easily be carried out in

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Diagnosis of Childhood Hypertension: Is Blood Pressure Height Ratio Useful?

Adekanmbi A.F,* Adejumo A.O***, Obadina O.O**

Original Article

Corresponding Author ( )

Dr Adekanmbi A.FDepartment of Paediatrics Olabisi Onabanjo University Teaching Hospital, Sagamu Ogun State. Tel : 08068925991Email : [email protected]

* Reader, Department of Paediatrics , Olabisi Onabanjo University Teaching Hospital, Sagamu Ogun State

*** Lecturer 1, Department of Community Health and Primary Care Lagos State University Teaching Hospital ,Lagos State

** Senior Registrar, Department of Paediatrics , Olabisi Onabanjo University Teaching Hospital, Sagamu Ogun State

Manuscript first received on the 5/04/17, peer reviewed and accepted for publication on 20/06/17

Abstract

Background: Hypertension is on the increase in children, the method of diagnosis is tedious. Newer methods have been suggested.

Objective: To assess the usefulness of Blood Pressure height ratio indices in t h e d i a g n o s i s o f c h i l d h o o d hypertension.

Methods: A descriptive cross sectional study was conducted among adolescents selected by a multistage sampling technique. Weight and height were measured using standard methods. Blood pressure was also recorded according to the standard method. Systolic and diastolic blood pressure to height ratio were then calculated. Receiver operating curves was used to assess the ability of systolic blood and diastolic blood pressure height ratio to discriminate childhood prehypertension and hypertension. For all statistical tests P < 0.05 was considered statistically

significant.

Results: Total of 984 subjects were studied. Female made up 59.5%. Pre-hypertension was present in 4.6% and hypertension in 5.2%. Diastolic blood pressure height ratio was 0.41±0.07 and 0.43±0.06 in both male and female. (t=3.294, p=0.001). Area under the curve (AUC) for systolic pre-hypertension in both gender were 0.790 and 0.701 respectively. It is 0.9 for systolic hypertension and 0.08 for diastolic hypertension respectively. Sensitivity and specificity ranged between 0.7-1.0 .

Conclusion: It was concluded that blood pressure to height ratio can be used in screening adolescents for detection of both prehypertension and hypertension.

Keywords: Pre-hypertension, Hypertension, Systolic blood pressure to height ratio, Diastolic blood pressure to height ratio, Adolescents.

Afr J Paed Nephrol 2017; 4:18-27

the physician's office during a busy clinic unlike the standard auscultatory method where expertise is required. There are reports on the geograph ic va r i ab i l i t y i n

anthropometry and blood pressure. A study from an urban area in southwestern Nigeria

13 showed that the method is highly sensitive .However no report have been documented on the sensitivity of this method among children and adolescents from semi urban and south-western area of Nigeria. Therefore this study assessed the usefulness of blood pressure height ratio indices in the diagnosis of childhood hypertension in a semi urban area of south western Nigeria.

Materials and Methods.Study design:A descriptive cross sectional study to assess the usefulness of blood pressure height ratio indices in the diagnosis of childhood hypertension was conducted

Study background: The study is a cross sectional study carried out in Sagamu ,Local Government Area Local Government Area (LGA) in Ogun State. It is one of the four major towns in Ogun State. There are 15 political wards in Sagamu LGA and it has a population of 228,382 according to the National Population

14Census of 2007 . Sagamu is predominantly semi- urban. There are 10 public and 22 private secondary schools.

Subjects selection: As part of the celebration of the World Kidney day in 2016, one private and one government secondary schools were purposively selected for sensitization on the importance of monitoring blood pressure of children and

adolescents.

Ethical consideration: Assent and informed consent forms were given to pupils of selected schools. The parents were informed through the school authority days before the world kidney day. Forms were then given to the students to take home. Student with signed forms from parents and who also gave verbal assent were recruited.

Data collection: On recruitment into the study, a proforma was used to obtain socio-demographic details of the students, thereafter students' weight, height and blood pressure were measured .Health scale manufactured by Easy Way Medical England

© RGZ -160 R was used to measure students' weight and height to the nearest 0.1kg and 0.1 cm respectively using standard procedures. The health scale records both weight and height. Quality was assured by 2 researchers repeating the measurements after every ten measurements and checking for zero error. Blood pressure reading was done using standard mercury sphygmomanometer and appropriate sized cuff. Before recording subjects were allowed to rest for 10minutes. Systolic and diastolic blood pressure was recorded at the first and fifth korotkoff sounds respectively. Average of two readings taking 10minutes apart was taken as the subject

2 blood pressure.

Definition of outcome variables: Pre th thhypertension: ≥ 90 -<95 percentile;

thHypertension ≥ 95 percentile; Stage 1 th th

hypertension: 95 -99 percentile +5mmHg; thStage 2 hypertension: >99 percentile+5

mmHg. Blood pressure >120/80mmHg but

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Adekanmbi A.F,* Adejumo A.O***, Obadina O.O**Diagnosis of Childhood Hypertension:Is Blood Pressure Height Ratio Useful?


th<90 percentile was defined as pre-15

hypertension . Normal blood pressure in adolescents 18years and above was taken as 120/80mmHg. Pre-hypertension:120-139/80-89mmHg; Stage 1hypertension: 140-1 5 9 / 9 0 - 9 9 m m H g ; S t a g e 2 hypertension>160/100mmHg.

Systol ic blood pressure to height ratio(SBPHR) and diastolic blood pressure ratio (DBPHR) were calculated as follows SBP (mmHg / height in cm and DBP (mmHg/ height in cm respectively.

Statistical analysisData were entered and analyzed using the Statistical Package for Social Sciences IBM (SPSS) version 19. Means and standard deviation of numerical variables were determined while categorical data were represented as percentages. Statistical significance for categorical data was determined using the Chisquare test while Student's t-test was used to compare two means. Receiver operating curves (ROC) were generated to test the ability of the SBPHR and DBPHR to detect pre-hypertension and hypertension in males and females independently. The discriminatory ability of SBPHR and DBPHR was measured by the area under the curve (AUC) and classified as follows: 0.9 to < 1: Excellent, 0.8 < 0.9: Good, 0.7 < 0.8: Worthless, and 0.6–< 0.7: Not good.16. The points where maximal sensitivity and specificity were achieved along the curve was taken as the optimal cut-off points. For all statistical test P < 0.05 was considered statistically significant.

Results : Total number of subjects screened

were nine hundred and eight –four. Females constituted 59.5% (585) f the population. Age range of the subjects was10 -18 years. The mean age of the subjects was 13.3±1.9years. The mean weight of male subjects 46.9±11.4kg was higher than the female 45.2±12.4kg (p=0.026). There was no gender difference in the mean height of study subjects (male = 155±10.0cm versus 154.7±8.0cm in females.) (p=0.096) ,(Table 1). The mean SBPHR and DBPHR of females was significantly higher than the males (p =0.001). However, there was no gender difference in the mean weight, height systolic or diastolic blood pressure (p>0.05).(Table 2 ) . Ta b l e 3 s h o w s t h a t s y s t o l i c prehypertension was present in 4.6%(45)and hypertension in 5.2%(81)and the proportion with diastolic pre-hypertension and hypertension were 8.8% and 4.5% respectively. More males (5.3%) than females (4.1%) had systolic prehypertension but more females (9.2%) than males (6.8%) had systolic hypertension (p >0.05). A higher proportion of females compared with males had both diastolic prehypertension and hypertension. The ability of SBPHR and DBPHR to discriminate pre-hypertension and hypertension is depicted in Table 4. The area under the curve shows that SBPHR and DBPHR discriminated both systolic and diastolic hypertension in males and females bet ter than systol ic and dias tol ic prehypertension. The sensitivity and specificity of predicting prehypertension and hypertension is displayed in Table 5.The sensitivities and specificities of SBPHR and DBPHR were generally higher for both systolic and diastolic hypertension than for systolic and diastolic prehypertension for

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both gender. Figures 1-4 are the receiver operating curves showing the sensitivity and specificity of pre hypertension and hypertension in both gender.(the figures are key to interpretation of the blood pressure ratio used in calculating cut off points for specificity and sensitivity)

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Table 1: Age and gender distribution of weight, height blood pressures and blood pressure height ratio.



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Receiver operating curves for systolic blood pressure to height ratio and diastolic blood pressure to height ratio for discrimination between girls with and those without pre hypertension.

Diagonal segments are produced by ties.

1 - Specificity

0.00.0

0.2 0.4 0.6 0.8 1.0

1.0

0.8

0.6

0.4

0.2

Se

ns

itiv

ity

Source of theCurve

SBPHR

DBPHR

Reference Line

ROC Curve

SEX: Female



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Receiver operating curves for systolic blood pressure to height ratio and diastolic blood pressure to height ratio for discrimination between boys with and those without hypertension.

Receiver operating curves for systolic blood pressure to height ratio and diastolic blood pressure to height ratio for discrimination between girls with and those without hypertension.



DiscussionThe prevalence of systolic and diastolic hypertension in the present study was 5.2% and 4.5% respectively. These prevalence are higher than previously reported prevalence of 1.7% in the same environment by Adekanmbi

17et al , this may be due to different sampling methods and diagnostic criteria for hypertension used. A study from Iran has also reported the prevalence of 4.17% and 4.33% for systolic and diastolic hypertension respectively amongst adolescents. Higher prevalence of 6.4%-13% have also been reported in Tunisia and Germany while 3.2%

18-21and 15% were reported in Texas and USA. These findings underscore the need for early monitoring of blood pressure in children and a d o l e s c e n t s . A l t h o u g h d e a t h a n d cardiovascular disability do not occur in children, the intermediate markers of end organ damage can be seen in them, it is therefore imperative to monitor blood

.17,18pressure as early as feasible Systolic pre hypertension and diastolic hypertension was present in 4.6% (45) and 8.8% (87) sing the area under the curve for both gender, there is an excellent ability to predict blood pressure status(AUC 0.970 Vs 0.941 in SBP and DBP hypertension).This is similar to the reported value in China by Xi B et al though when age categories were considered the values in this study is slightly lower. This may be due to difference in age stratification of both studies. It may also be due to different study designs used in the study. The China study was a review of records as opposed to descriptive

21cross-sectional nature of the present study. The DBPHR (0.41-0.43) of the current study is a poor predictor of diastolic hypertension for both gender in contrast to Lu Q et al. and

8,11, 22,23 Ahmed et al where values ranged from

0.51-0.60 and 0.52. In summary BPHR is a useful tool in screening for hypertension and prehypertension in children and could be employed in epidemiological surveys for early identification of hypertension in children. It has been demonstrated in this study to be sensitive and specific particularly for systolic hypertension in both gender (0. 9-1.0) but less sensitive for DBPHR across the ages. Blood pressure height ratio used in this study to screen for hypertension and prehypertension can be said to compare favourably well with other studies across the globe regardless of the study design. The relatively high sensitivity and specificity of the method make it a useful tool for early detection of both prehypertension and hypertension in children.

ConclusionThis study has demonstrated that blood pressure height ratio has high sensitivity and specificity and could be used as a screening tool to detect childhood hypertension for early referral for subsequent evaluation.

Acknowledgment: Dr Oyebisi O.O and 500level medical students who participated in data collection are hereby acknowledged. Sources of funding: Self funded

Authors contributions: Adekanmbi A.F conceived and designed the study, participated in data collection. Obadina O.O participated in data collection. Adejumo O.A carried out data analysis. All authors drafted the manuscript and agreed on the final draft.

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Conflict of interest: None

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27Afr J Paed Nephrol 2017; 4:18-27


adekanmbi a.f,* diagnosis of childhood hypertension: is blood pressure adejumo a.o ... of...

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