Analysis of Urine Test Results of Han and Tibetan 0- 6 Years Old Children in Gansu Province, Western China: A Cross-Sectional Study

Yanfen Li Northwest Minzu University Hongbo Pei (  peihb@lzu.edu.cn ) Institute of Epidemiology and Biostatistics, School of Public Health, Lanzhou University. https://orcid.org/0000-0003-0943-5900 Hao Qiu Second provicial People's Hospital of Gansu Jinqiao Cui Northwest Minzu University Liang Ma Sichuan University West China Hospital Ping Fu Sichuan University West China Hospital Xiaoyan Zhen School of public health, Lanzhou University


Conclusion
The differences in physiology, diet, and living environment in children belonging to different ethnic groups were in uencing factors for different urine abnormalities.
Background Kidney disease has been described as the most neglected chronic disease [1]. Chronic kidney disease has posed serious health damage and a heavy economic burden on human beings. Kidney disease in children often occurs insidiously and may develop into chronic nephropathy [2]. The incidence and morbidity of kidney disease in children tend to increase [3]. Urine examination can better re ect kidney and urinary system diseases, which is an important means for the early detection of kidney disease [4]. As early as in the 1960s and 1970s, developed countries such as Japan, South Korea, and Singapore used urine screening for primary and secondary school students as one of the measures for children's health. The detection rate of latent nephropathy in local children improved [5]. Routine urine examination has been used as an early screening and prognostic measure for kidney diseases in many countries around the world [6] [7] [8] [9]. In Asia, Japan, South Korea, Taiwan, and China have launched a regular urine screening program for children and adolescents [10] [11] [12]. China's western region is sparsely populated, and its economic development is lagging behind. Ethnic and frontier areas are two main characteristics of the region. In these places, Tibetans, who are characterized by high-altitude living and Buddhism, are different from Han in terms of diet, lifestyle, and cultural characteristics [13]. Using regular urine tests, this study examined the morning urine of children aged 0-6 years in Lanzhou City and

Urine routine test
The urine samples of children visiting the outpatient clinic were taken for a routine urine examination using a dry chemical analyzer and urine sediment detection [4]. The morning mid-stage urine was collected and tested immediately after on-site collection by uni ed training testing staff using a uni ed standard method so as to control the quality of urine examination.
Information collection using the questionnaire The children were surveyed using the questionnaire designed by the research group. The contents of the questionnaire comprised the children's personal status, environmental exposure, diet, parents' age, parents' education level, parents' income status and parents' history of kidney disease. These parents lled the questionnaire, and the investigator on the spot checked and collected the questionnaire.

Statistical analysis
Important indicators of the detection rate of urine in the two ethnic groups of children were analyzed by case-control analysis. Children with abnormal urine test results formed the case group. Children with negative test results formed the control group (case:control = 1:3; vitamin C level 1:1). The correlations between abnormal urine results and the following factors were analyzed: personal conditions (body mass index, BMI), environmental exposure (harmful environmental factors including heavy metals, pesticides, chemicals, high temperature, high humidity, electromagnetic radiation, noise, and so on). "Frequently passive smoking" meant that the same occupants smoked more than one time per day for more than15 min in the children's living environment. "Residing in newly decorated houses" meant that the children lived in newly renovated houses within 1 year before and after birth, and the dietary status ("food intake") was determined by comparison with peers. "Frequent intake of lead-containing foods" referred to eating lead-containing pine eggs, popcorn, and animal offal more than two times a week).

Diagnostic criteria
Urine vitamin C, protein, red blood cells, white blood cells, nitrite, glucose, bilirubin, urobilinogen, ketone bodies, and so forth are semi-quantitative indicators divided into "-," "+-," "+," "++," and " +++." IA detection Indicator with one or more "+" is de ned as positive. The occult blood-positive patients were examined by urinary sediment microscopy. The red blood cells more than 3/HP (per high-power eld) indicated a positive result. The white blood cell-positive patients were reviewed by urinary sediment microscopy, and the standard was more than 5/HP.

Statistical analysis
The database was built using Epidata3.1 data management software, and the occurrence of an abnormal urine test in Han and Tibetan children was described using SPSS22.0 and EXCEL2010. The differential detection of the indicators between the two ethnic groups was conducted using the c 2 test. The multivariate logistic regression analysis was used to explore the possible in uencing factors for abnormal urine. The case group comprised children with abnormal urine test results. The control group comprised children with normal urine test results. The detection results of indicators revealed that the ratio of the sample of the case group to the sample of the control group was 1:3, but it was 1:1 for the vitamin C level.  Table 2 .

Results
The positive detection rate of urine vitamin C in Han and Tibetan children was 41.32% and 18.21%, respectively, with a statistically signi cant difference (P < 0.001). The positive detection rate of ketone bodies was 5.99% and 17.57%, respectively, with a statistically signi cant difference (P < 0.001). The positive detection rate of urinary bilirubin was 2.06% and 0.80%, respectively, with a statistically signi cant difference (P = 0.046). The detection rate of urinary protein was 0.39% and 3.83%, respectively, with a statistically signi cant difference (P < 0.001). The abnormal detection rate of other indicators among children in the two ethnic groups was not statistically signi cantly different, as shown in Table 3.
The results of multivariate logistic regression analysis showed that the detection rate of urine vitamin C in Han boys was 1.385 times that in girls (95% CI = 1.041-1.842). Among Han children, the positive detection rate of urine vitamin C in the 1-year-old group was lower than that in the 4-to 6-year-old group (OR = 0.208, 95% CI = 0.086-0.507); and the rate in the 1-to 3-year-old group was lower than that in the 4to 6-year-old group (OR = 0.128, 95% CI = 0.052-0.313). Parents' histories of kidney disease was a risk factor (OR = 2.506, 95% CI = 1.661-3.781). In Tibetan children, the positive detection rate of urine vitamin C in the 1-to 3-year-old group was higher than that in the 4-to 6-year-old group (OR = 3.011, 95% CI = 1.277-7.096); living in the passive smoking environment was a risk factor for urine vitamin C (OR = 1.919, 95% CI = 1.102-3.340). The detection rate of urine ketone body in Han boys was 2.283 times that in girls (95% CI = 1.203-4.333). In Tibetan children, age, lead-containing foods, and living in newly decorated houses for a long time were in uencing factors for the urine ketone body. The detection rate of urinary white blood cells in boys of both ethnic groups was lower than that in girls (OR Han = 0.095, 95% CI  Table 4.

Discussion
Routine urine tests have been conducted in a few developed cities in China for children with chronic occult kidney disease. However, data among children from ethnic minority areas in western China are rarely reported. Urine white blood cells, urine occult blood, and urine protein are commonly used to initially detect and analyze the occurrence of latent nephropathy in children. A comparison of urine test results of Han and Tibetan children revealed that the detection rate of urinary protein was higher in Tibetan children than in Han children. In this study, for urinary protein, the multivariate analysis was not carried out because of fewer children with positive results for urinary protein. The in uencing factors for urine protein detection in the two ethnic groups need further exploration.
Other multivariate regression analysis showed that male sex was a protective factor for urinary white blood cells, which might be related to girls' short urethra, urethral opening close to the anus, and easy contamination by feces, causing urinary tract infection. The results of this study showed that "frequent intake of lead-containing foods" was a risk factor for urinary white blood cells in Tibetan children. At present, few studies have been conducted on the correlation between urinary white blood cells and lead exposure [14]. The ability of kidneys to resist in ammation caused by blood-borne pathogens might be weakened by the effect of lead intake on kidney structure and function [15]. However, since blood-borne infections account for less than 3% of urinary tract infections, the in uence of lead intake on kidney needs further con rmation.
Male sex is a protective factor for urinary white blood cells in both Han and Tibetan children [16].
Urinary occult blood is mainly used for the diagnosis of kidney and urinary tract diseases [17]. The present study showed that a history of parental kidney disease was the risk factor for urinary occult blood found in Han children [18]. Age 4-6 years and "residence in newly decorated houses" were the risk factors for urinary occult blood in Tibetans. Newly decorated houses contain harmful chemical substances such as formaldehyde and benzene series. Toxicological studies have shown that gaseous formaldehyde can cause obvious oxidative damage to kidney tissue [19] [20]. Increased exposure to environmental risk factors increases the positive detection rate of urinary occult blood in growing children.
The nutritional status is essential for healthy kidneys in children [21]. The present study found that the positive rate of urinary vitamin C was higher in Han than in Tibetan children. The results of multivariate regression analysis showed that the lower age group (1-3 years old) was a protective factor for urinary vitamin C compared with the higher age group (4-6 years old) in Han children. However, the risk factors in Tibetan children were unclear. The reason for the analysis might be related to the eating habits of Han and Tibetan children. Tibetans prefer to eat beef, mutton, and dairy products, and have less intake of vegetables and fruits [22]. Han children started consuming complementary foods with increasing age. Also, the ingestion of a variety of vegetables and fruits gradually increased, resulting in the high detection rate of urine vitamin C in the higher age group. However, Tibetan children ingested less vegetables and fruits, leading to a low detection rate of vitamin C in the higher age group. This study also showed that a passive smoking environment and parents' history of kidney disease were both risk factors. Also, smoking cessation restored the renal protective effect of ACEIs by reducing renal and oxidative stresses, suggesting that parents should pay attention to children's daily life and environmental health so as to prevent environmental damage to kidneys of children, especially children with a family history of kidney disease.
A positive detection rate of urinary ketone bodies is more common in diabetic ketoacidosis, nondiabetic ketosis, stress, exercise, fasting, infectious diseases, severe diarrhea, vomiting, and so in [23]. The present study found that the positive rate of ketone bodies was lower in Han children than in Tibetan children.
The multivariate regression analysis showed that the positive rate of ketone bodies was higher in boys than in girls among Han children, and the detection rate of ketone bodies was higher in the higher age group (4-6 years old) than in the lower age group (1-3 years old) in Tibetan children. It might be due to more daily activities of Tibetan children compared with Han children, boys compared with girls, and the higher age group compared with the lower age group. These factors led to increased fat metabolism and relative insu ciency of carbohydrates, resulting in positive detection of ketone bodies. Among Tibetan children, "residence in newly renovated decorated houses" was a risk factor for the detection of urine ketone bodies. The decoration materials contain many harmful chemicals, and therefore it is suggested that parents should pay more attention to children's living environment.

Conclusions
The differences in physiology, diet, and living environment of children in different ethnic groups may be fundamental in uencing factors for urine abnormalities. Further, the susceptibility of girls' urinary system is worthy of attention. Hence, health education for children and their parents should be strengthened. Also, good hygiene habits, reasonable intake of nutrients, avoidance of lead-containing foods, and healthy living environment should be promoted. At the same time, children should be encouraged to actively participate in urine screening to prevent childhood kidney disease.

Declarations
Ethics approval and consent to participate The present study was approved (approval no. gssdermyyyxllzfh201605) by the Ethics Committee in The Second People's Hospital of Gansu Province, China. The participation of children and their parents in the present study was voluntary. Written informed consent was obtained from a parent for participants under 16 years old.

Consent for publication
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