Urinary calcium to creatinin ratio in children
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《美国医学杂志》
1 Department of Pediatric Nephrology ,Babol Medical University, Iran
2 Department of Social Medicines and Health Babol Medical University, Iran
Abstract
Due to difficulty of 24hr urine collection in children for detection of hypercalciura, random urine calcium to creatinin ratio (U Ca/Cr) has been used for screening hypercalciuria. The purpose of this study was to determine normal U Ca/Cr ratio in primary school age children in North of Iran. This study was performed on 590 healthy school-age children, aged between 7-11 years. Early morning random urine samples from all children were analyzed for calcium and creatinine. Mean value and 95th percentile for U Ca/Cr ratio were 0.155 ± 0.095 and 0.36, respectively. A negative correlation observed between age and U Ca/Cr ratio was R=-0.101, P=0.014. With regard to variations in U Ca/Cr ratio among different studies, it is recommended to determine this ratio in every geographic area
Keywords: Children; Ca to Cr ratio; Hypercalciuria
The most important ion in the musculoskeletal system is calcium, and kidney is the major organ for calcium, homeostasis.[1] Hypercalciuria could be associated with frequency, dysuria syndrome, enuresis, abdominal pain, hematuria and urolithiasis. Calcium has been known as the most important element in most renal stones. Calcium excretion of more than 4 mg/kg in 24hr urine has been defined as hypercalciuria. [2],[3] It is difficult to take the accurate 24 hr urine in young and non-toilet trained children, so hypercalciuria can be screened by random urine calcium to creatinin ratio. [4],[5],[6] Many authors reported that U Ca/Cr ratio varies in different ages and geographic areas. [5],[6],[7] This study was done to determine U Ca/Cr ratio in school age children (North of Iran, near Caspian sea).
Methods and Materials
Case selection: 590 children (298 girls and 292 boys) aged between 7 to 11 years were randomly selected from 6 primary schools between March and May 2003. All of them had normal physical examination, growth and blood pressure, and were told not to change their eating habits and physical activities. Children with positive history of renal disease, hematuria, chronic disease, and metabolic disorders and malnutrition were excluded. Early morning samples were used to determine calcium and creatinin.
Urine examination: Urine calcium and creatinine were measured by the cresolphthalein complexont spectophotometric method[8] and kinetic jaffe reaction, respectively. Hitachi 704 automated analyzer was used, and then urinary Ca/Cr (mg/mg) ratio was calculated.
Statistical analysis: Data was statistically analyzed by students t-test; analysis of variance (ANOVA), P<0.05, was considered significant.
Results
From all the cases, 298 (50.5%) were girls and 292 (49.5%) were boys. Mean ratio of urine Ca/Cr in all children was 0.155 ± 0.095; for girls and boys, this ratio was 0.16 ±0.1 and 0.15 ± 0.09 respectively. 95th percentile and mean values for U Ca/Cr decreased by ageing. Pearson correlation coefficient test showed a negative correlation between age and U Ca/Cr ratio table1. Mean and 95th percentile ratio did not show a significant difference in both sexes table2.
Discussion
In children, urinary solute/Cr ratio is a useful and reliable method for determining hypercalciuria and also is a non-invasive and relative inexpensive method. [9],[10]Reusz showed that there is a relationship between the first morning and 24 hr urine Ca/Cr ratio.[7] For every age-group, different urine Ca/Cr ratio was reported.[4], [11],[12] These differences may be due to exposure to sun light, climate, genetics, nutritional habits, drinking water and ethnicity. [12],[13]
In North of Iran, it was seen an inverse relationship between 95th percentile and mean value of U Ca/Cr ratio, with ageing in children that was reported by others. [8],[9],[14],[15] Ceran reported that children under 7 months have 3-fold higher U Ca/Cr ratio compared to ones above 7 years.[15] Also, So showed U Ca/Cr ratio decreased by aging.[16] Safarinejed showed intra-individual and inter-individual variations of U Ca/Cr ratio markedly decrease by ageing (1 month to 7-years-old), but only a little changes were seen in 7-14-years-old.[14] Sagren et al suggested that high level U Ca/Cr ratio in infants may be secondary to low creatinin excretion per unit body mass.[4]
As previous reports[11],[14],[15] there was no difference in U Ca/Cr ratio between both sexes. 95th percentile for U Ca/Cr ratio in our study was 0.36. The result obtained was the same as some reports and different with others.[9],[14],[15],[16],[17] Although, in some studies, it was seen different in different age groups.[5],[6],[11],[15],[16],[17],[18] In conclusion, some studies showed different U Ca/Cr ratio in various geographic areas. So, it was recommended to determine this ratio in different pediatric age-groups and geographic areas.
Acknowledgment
Research Council of Babol Medical University supported this study. We thank Boali laboratory personals for their expert laboratory assistance.
References
1. Spitzer A, Chensy RW. Role of the kidney in mineral metabolism. In Edelman C Jr, Bernstein J, Meadow SR et al, eds . Pediatrics Kidney Disease . 2nd edn. Little Brown and Company, 1992; 147-184
2. Moxey-Mims MM, Stapleton FB. Hypercalciuria and nephrocalcinosis in children. Curr Opin Pediatr 1993; 5: 186-190.
3. Stapleton FB.Idiopatic hypercalciuria: association with isolated hamaturia and risk for urolithiasis in children. The Southwest Pediatric Nephrology Study Group. Kidney Int 1990; 37 : 807-811.
4. Sargent JD, Stukel TA, Kresel J. Normal values for random urinary calcium to creatinin ratios in infancy. J Pediatr 1993; 123: 393-397.
5. Matos V, Van Melle G, Boulat O et al. Urinary phosphate/creatinin, calcium /creatinin and magnesium/creatinin ratios in a healthy pediatric population. J Pediatr 1997; 131: 252-257.
6. Esbjorner E, Jones IL. Urinary calcium excretion in Swedish children. Acta Pediatr 1995; 34 : 156-159.
7. Reusz GS, Dobos M, Byrd D et al. Urinary calcium and oxalate excretion in children 1995; 9: 39-44
8. Lorentz K. Improved determination of serum calcium with 2-cresolphthalein Complexone. Clin Chem Acta 1982; 126; 327-334.
9. Kaufman JM, Martin LG, Seegmiller JE. Urine uric acid to creatinin ratio, a screening test for inherited disorders of purine metabolism. J Pediatr 1968; 4: 583-592.
10. Ginsbery JM, Chang BS, Matarese RA et al. Use of single voided urine samples to estimate proteinuria. N Eng J Med 1993; 309 : 1543-1546.
11. Chen Y H, Lee AJ, Chen CH et al. Urinary mineral excretion among normal Taiwanese children. Pediatr Nephrol 1994; 8: 36-39.
12. Sweid HA, Bagga A, Vasvani M et al. Urinary excretion of minerals, oxalate and uric acid in north Indian children. Pediatr Nephrol 1997; 11 : 189-192.
13. Juuti M, Heinonen P, Alhava EN. Seasonal variation in urinary excretion of calcium, oxalate, magnesium, and phosphate on free and standard diet in men with urolithiasis. Scan J Urol Nephrol 1981; 15 : 137-141.
14. Safarinejad MR. Urinary mineral excretion in healthy Iranian children. Pediatr Nephrol 2003: 18: 140-144.
15. Caren O, Akin M, Akturk Z. Normal urinary/ creatinin ratios in Turkish children. Indian Pediatrics 2003; 40: 884-887.
16. So NP, Osorio AV, Simon SD et al. Normal urinary calcium/creatinin ratios in African-American and Caucasian children. Pediatr Nephrol 2001; 16: 133-139.
17. Rath B, Aggarwal MK, Mishra TK, Talukdar B, Murthy NS, Kabi BC.Urinary calcium creatinine ratio and hypercalciuria. Indian Pediatr 1994; Mar; 31(3): 311-316.
18. Vachvanichsanong P, Lebel L, Moore ES. Urinary calcium excretion in healthy Thai children. Pediatr Nephrol 2000; Aug; 14(8-9): 847-850.(Sorkhi Hadi, Haji Aahmadi)
2 Department of Social Medicines and Health Babol Medical University, Iran
Abstract
Due to difficulty of 24hr urine collection in children for detection of hypercalciura, random urine calcium to creatinin ratio (U Ca/Cr) has been used for screening hypercalciuria. The purpose of this study was to determine normal U Ca/Cr ratio in primary school age children in North of Iran. This study was performed on 590 healthy school-age children, aged between 7-11 years. Early morning random urine samples from all children were analyzed for calcium and creatinine. Mean value and 95th percentile for U Ca/Cr ratio were 0.155 ± 0.095 and 0.36, respectively. A negative correlation observed between age and U Ca/Cr ratio was R=-0.101, P=0.014. With regard to variations in U Ca/Cr ratio among different studies, it is recommended to determine this ratio in every geographic area
Keywords: Children; Ca to Cr ratio; Hypercalciuria
The most important ion in the musculoskeletal system is calcium, and kidney is the major organ for calcium, homeostasis.[1] Hypercalciuria could be associated with frequency, dysuria syndrome, enuresis, abdominal pain, hematuria and urolithiasis. Calcium has been known as the most important element in most renal stones. Calcium excretion of more than 4 mg/kg in 24hr urine has been defined as hypercalciuria. [2],[3] It is difficult to take the accurate 24 hr urine in young and non-toilet trained children, so hypercalciuria can be screened by random urine calcium to creatinin ratio. [4],[5],[6] Many authors reported that U Ca/Cr ratio varies in different ages and geographic areas. [5],[6],[7] This study was done to determine U Ca/Cr ratio in school age children (North of Iran, near Caspian sea).
Methods and Materials
Case selection: 590 children (298 girls and 292 boys) aged between 7 to 11 years were randomly selected from 6 primary schools between March and May 2003. All of them had normal physical examination, growth and blood pressure, and were told not to change their eating habits and physical activities. Children with positive history of renal disease, hematuria, chronic disease, and metabolic disorders and malnutrition were excluded. Early morning samples were used to determine calcium and creatinin.
Urine examination: Urine calcium and creatinine were measured by the cresolphthalein complexont spectophotometric method[8] and kinetic jaffe reaction, respectively. Hitachi 704 automated analyzer was used, and then urinary Ca/Cr (mg/mg) ratio was calculated.
Statistical analysis: Data was statistically analyzed by students t-test; analysis of variance (ANOVA), P<0.05, was considered significant.
Results
From all the cases, 298 (50.5%) were girls and 292 (49.5%) were boys. Mean ratio of urine Ca/Cr in all children was 0.155 ± 0.095; for girls and boys, this ratio was 0.16 ±0.1 and 0.15 ± 0.09 respectively. 95th percentile and mean values for U Ca/Cr decreased by ageing. Pearson correlation coefficient test showed a negative correlation between age and U Ca/Cr ratio table1. Mean and 95th percentile ratio did not show a significant difference in both sexes table2.
Discussion
In children, urinary solute/Cr ratio is a useful and reliable method for determining hypercalciuria and also is a non-invasive and relative inexpensive method. [9],[10]Reusz showed that there is a relationship between the first morning and 24 hr urine Ca/Cr ratio.[7] For every age-group, different urine Ca/Cr ratio was reported.[4], [11],[12] These differences may be due to exposure to sun light, climate, genetics, nutritional habits, drinking water and ethnicity. [12],[13]
In North of Iran, it was seen an inverse relationship between 95th percentile and mean value of U Ca/Cr ratio, with ageing in children that was reported by others. [8],[9],[14],[15] Ceran reported that children under 7 months have 3-fold higher U Ca/Cr ratio compared to ones above 7 years.[15] Also, So showed U Ca/Cr ratio decreased by aging.[16] Safarinejed showed intra-individual and inter-individual variations of U Ca/Cr ratio markedly decrease by ageing (1 month to 7-years-old), but only a little changes were seen in 7-14-years-old.[14] Sagren et al suggested that high level U Ca/Cr ratio in infants may be secondary to low creatinin excretion per unit body mass.[4]
As previous reports[11],[14],[15] there was no difference in U Ca/Cr ratio between both sexes. 95th percentile for U Ca/Cr ratio in our study was 0.36. The result obtained was the same as some reports and different with others.[9],[14],[15],[16],[17] Although, in some studies, it was seen different in different age groups.[5],[6],[11],[15],[16],[17],[18] In conclusion, some studies showed different U Ca/Cr ratio in various geographic areas. So, it was recommended to determine this ratio in different pediatric age-groups and geographic areas.
Acknowledgment
Research Council of Babol Medical University supported this study. We thank Boali laboratory personals for their expert laboratory assistance.
References
1. Spitzer A, Chensy RW. Role of the kidney in mineral metabolism. In Edelman C Jr, Bernstein J, Meadow SR et al, eds . Pediatrics Kidney Disease . 2nd edn. Little Brown and Company, 1992; 147-184
2. Moxey-Mims MM, Stapleton FB. Hypercalciuria and nephrocalcinosis in children. Curr Opin Pediatr 1993; 5: 186-190.
3. Stapleton FB.Idiopatic hypercalciuria: association with isolated hamaturia and risk for urolithiasis in children. The Southwest Pediatric Nephrology Study Group. Kidney Int 1990; 37 : 807-811.
4. Sargent JD, Stukel TA, Kresel J. Normal values for random urinary calcium to creatinin ratios in infancy. J Pediatr 1993; 123: 393-397.
5. Matos V, Van Melle G, Boulat O et al. Urinary phosphate/creatinin, calcium /creatinin and magnesium/creatinin ratios in a healthy pediatric population. J Pediatr 1997; 131: 252-257.
6. Esbjorner E, Jones IL. Urinary calcium excretion in Swedish children. Acta Pediatr 1995; 34 : 156-159.
7. Reusz GS, Dobos M, Byrd D et al. Urinary calcium and oxalate excretion in children 1995; 9: 39-44
8. Lorentz K. Improved determination of serum calcium with 2-cresolphthalein Complexone. Clin Chem Acta 1982; 126; 327-334.
9. Kaufman JM, Martin LG, Seegmiller JE. Urine uric acid to creatinin ratio, a screening test for inherited disorders of purine metabolism. J Pediatr 1968; 4: 583-592.
10. Ginsbery JM, Chang BS, Matarese RA et al. Use of single voided urine samples to estimate proteinuria. N Eng J Med 1993; 309 : 1543-1546.
11. Chen Y H, Lee AJ, Chen CH et al. Urinary mineral excretion among normal Taiwanese children. Pediatr Nephrol 1994; 8: 36-39.
12. Sweid HA, Bagga A, Vasvani M et al. Urinary excretion of minerals, oxalate and uric acid in north Indian children. Pediatr Nephrol 1997; 11 : 189-192.
13. Juuti M, Heinonen P, Alhava EN. Seasonal variation in urinary excretion of calcium, oxalate, magnesium, and phosphate on free and standard diet in men with urolithiasis. Scan J Urol Nephrol 1981; 15 : 137-141.
14. Safarinejad MR. Urinary mineral excretion in healthy Iranian children. Pediatr Nephrol 2003: 18: 140-144.
15. Caren O, Akin M, Akturk Z. Normal urinary/ creatinin ratios in Turkish children. Indian Pediatrics 2003; 40: 884-887.
16. So NP, Osorio AV, Simon SD et al. Normal urinary calcium/creatinin ratios in African-American and Caucasian children. Pediatr Nephrol 2001; 16: 133-139.
17. Rath B, Aggarwal MK, Mishra TK, Talukdar B, Murthy NS, Kabi BC.Urinary calcium creatinine ratio and hypercalciuria. Indian Pediatr 1994; Mar; 31(3): 311-316.
18. Vachvanichsanong P, Lebel L, Moore ES. Urinary calcium excretion in healthy Thai children. Pediatr Nephrol 2000; Aug; 14(8-9): 847-850.(Sorkhi Hadi, Haji Aahmadi)