The prevalence of orthostatic proteinuria among schoolchildren in Muratpaşa district in Antalya

Although it is reported that orthostatic proteinuira (OP) is the most common cause of proteinuira in children, especially in adolescents, the number of studies regarding its prevalance is not satisfactory due to the benign characteristic of the disease; and in our country, as far as we know, no study exist on the frequency of OP in children. The aim of this study was to determine the prevalence of OP in healthy elementary and secondary school students (6-15 years old) in Antalya city centre, evaluating its relationship with age, gender and body mass index. 61092 students, aged between 6-15, from 124 elementary and secondary schools in Muratpaşa district in Antalya constituted the population in our study. Using cluster sampling method, 1500-2500 students in 64 classes chosen from 58 schools constituted our study group. Cases with chronic diseases, who were constantly using medicine, who don't want to give urine sample or whose parents' consents were not taken were excluded from the study. Height and weight measurements and urine samples were taken from all cases. Body mass index (BMI) was calculated using height (cm) and BW (kg); BMI <5p was classified as thin, 5-85p normal weight, 85-95p over weight and >95p as obese. In cases with a proteinuira level of 1+ and above in the first urine sample, in order to exclude temporary proteinuira, second and third urinary samples (at any time of the day) were taken within at least two weeks apart. The cases in which proteinuira was not determined in protein/creatine (UPe/UCr) ratio or in strip test were evaluated as temporary proteinuira; in cases with continuing proteinuira, first morning urine samples were collected. The cases in which proteinuira was not detected in first morning urine samples were diagnosed as orthostatic proteinuira. A total of 1701 children were taken in the study; 881 boys (51.8%) with a mean age of 10,5 ± 0,06 years. Proteinuira was detected in 64 cases (3,7%) in the first analysis. The frequency of orthostatic proteinuira was found as 0,64%. 8 of 11 cases were girls. It was observed that, though not statistically significant, OP was higher in children with an age group of 11-15 years compared to 6-10 years (0,63% vs. 0,36%). OP was highest in thin children (1,3%), whereas it was lowest in obese cases. Mean UPr/UCr ratio was 0,30±0,23 (0,21-1,30) mg/mg in children with OP. As a result, OP ratio was found relatively low in our study. However, it was still the most common cause of asymptomatic isolated proteinuira in children when temporary reasons were excluded. It was seen more commonly in thin children over 10 years of age . It was observed that proteinuira was variable and low to moderate in amount; apart from massive proteinuira cases, it seems quite impossible to distinguish OP and persistent proteinuira, considering the amount of urinary protein excretion.