Urinalysis findings, obesity and hypertension in Italian adolescents from world kidney day

Abstract

INTRODUCTION World Kidney Day (WKD) started in 2006 by a memorandum of understanding between the International Federation of Kidney Foundations (IFKF) and the International Society of Nephrology (ISN) based on a proposal to “raise awareness of the importance of our kidneys to our overall health and to reduce the frequency and impact of kidney disease and its associated health problems world-wide”. In Italy the WKD was planned and conducted by the Fondazione Italiana del Rene (FIR; National Kidney Foundation of Italy), in collaboration with the Italian Society of Nephrology (SIN) and the Red Cross of Italy. Italian WKD focused on two projects called ”Square project” and “School project”. The “Square project” was intended for general population and the “School project” for students attending the fourth and fifth year of Italian high school. This is a unique initiative in the context of those carried out around the world by countries that have observed WKD. The relevance of this screening relies on the fact that this population is seldom evaluated by either pediatricians or general practitioners in the absence of overt disease. The main goal of the present study was to assess the presence of urinalysis abnormalities and their associations with hypertension and obesity in a population of adolescents participating in the Italian Kidney Day during the period 2010–2011. METHODS Study population is represented by students participating to “school project”. Data on age, gender, sport activity and general information was assessed using questionnaires. Trained personnel (nephrologists and nurses) assessed systolic and diastolic BP (SBP; DBP). Weight, height and WC were measured. BMI, Ci and WHt-ratio were calculated. HTN was defined as SBP ≥ 140 mmHg and/or DBP ≥ 90 mmHg, pre-hypertension as SBP of 120 mmHg but lower than 140 mmHg or DBP of 80 mmHg but lower than 90 mmHg. Stage-1 HTN as SBP of 140 mmHg but lower than 160 mmHg or DBP of 90 mmHg but lower than 100 mmHg, and Stage-2 HTN as SBP ≥ 160 mmHg or DBP≥ 100 mmHg. Isolated systolic hypertension (ISH) as SBP ≥ 140 mmHg and DBP ≤ 90 mmHg. According to BMI, normal weight was from 18.5 to 24.9 kg/m2, overweight from 25 to 29.9 kg/m2, class-I obesity from 30,0 to 34.9 kg/m2, class-II from 35 to 39.9 kg/m2, class-III ≥ 40 kg/m2. Normal WC was <88 cm in female and <102cm in male. Urine test was performed with a dipstick; subjects were considered proteinuric when urine dipstick was positive for proteinuria ≥30 mg/dL. RESULTS: Data pertaining to 4550 students (median age:18 years; IQR:18-19) were analyzed both as a whole cohort, and divided on the basis of sex and 4 areas of our country – i.e. Northern, Central, Southern and Islands. Incident HTN was found in n. 71 (1.6%) participants (n.31 female; n.39 male). ISH was present in 7,6 % of students. In hypertensive participants (HP) median SBP and DBP were 144 mmHg (IQR:140-150) and 90 mmHg (IQR:90-94), respectively. Stage-1 HTN and Stage-2 HTN was present in 94.3% and 5.7% of HP, respectively. Overweight, class-I,II,III obesity percentage was 21.1, 10.1, 7.1, 1,4 in HP, respectively. Compared to participants without HTN, HP had median: BMI=23.7(IQR:21.9-27.8) Vs 21.8 (IQR:20.0-24.1), p=0.001; Ci=1.22 (IQR:1.16-1.31)Vs 1.21(IQR:1.14-1.29), p=0.527; WC= 88.0 (IQR:80.0-98.5) Vs 81.0 (IQR:74-89), p=0.001; WHt-ratio:0.50 (IQR:0.46-0.59) Vs 0.47 (IQR:0.44-0.52), p=0.001. Multivariate linear regression analysis showed that WHt-ratio was predictor of HTN (p=0.02) while WC was predictor of SBP (p=0.001) At urine dipstick, proteinuria was present in 14,7 %, leucocyturia in 14,5 %, hematuria in 8,6 %. The percentage of adolescents with normal weight was 73,1%, overweight 15,7%, class-I obesity 2,4 %, class-II obesity 0,7 %, class-III obesity 0,1 %. In univariate analysis proteinuria was associated (p=0.01) positively to SBP and pulse pressure but inversely to BMI; no association was found with other variables.In multivariable linear regression analysis no predictive factor was found among anthropometric indicators, urinary abnormalities and BP levels. CONCLUSIONS: “School project” of WKD is an important survey to the prevention of kidney diseases in young adolescents. Overweight and obesity are present in a significant percentage of our students. This phenomenon is strictly connected to the presence of HTN in our populations: WHt-ratio is significantly associated to the presence of HTN and WC is associated to levels of SBP. Independent from these factors, also albuminuria is quite often present in adolescents and it is associated with SPB and pulse pressure but not with anthropometric indicators. Other studies are necessary to understand the role of routine measurement of albuminuria in asymptomatic overweight and obese adolescents.