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With completing a baseline survey of a large natural population cohort, conducting regular follow-up has become a key factor in further improving the quality of cohort construction and ensuring its sustainable development. Typical cohort follow-up methods include repeat surveys, routine monitoring, and community-oriented surveillance. However, in practical applications, there are often issues such as high costs, difficulty, and high error rates. Telephone follow-up is an important supplementary method to the methods mentioned above, as it has the characteristics of low cost, fast response, and high quality. However, the with difficult organization, quality control is challenging, response rates are low, and management levels vary widely, which limits its widespread use in large-scale population cohort studies. Given the above problems, this study draws on customer relationship management based on the actual needs of the China Northwest Cohort follow-up. It relies on the REDCap electronic data collection platform to build a telephone follow-up management and quality control system. Targeted solutions are provided for key issues in telephone follow-up implementation, including organizational structure, project management, data collection, and process quality control, to improve the quality control level of telephone follow-up comprehensively and thereby enhance the quality and efficiency of follow-up. We hope to provide standardized follow-up programs and efficient quality control tools for newly established and existing cohort studies.

Objective: To study the relationship between the Chinese dietary guidelines compliance index for pregnant women (CDGCI&#95;PW) and congenital heart disease (CHD) in offspring. Methods: In a hospital-based case-control study conducted in Xi'an, Shaanxi province, semi-quantitative food frequency questionnaires were used to investigate the diets of pregnant women throughout pregnancy. The modified CDGCI&#95;PW score was used to evaluate dietary quality during pregnancy, logistic regression was applied to analyze the relationship between CDGCI&#95;PW score and offspring CHD, and the ROC curve was adopted to construct the prediction model of CDGCI&#95;PW for offspring CHD. Results: A total of 1 422 subjects were enrolled, including 474 in the case group and 948 in the control group. The CDGCI&#95;PW score in the case group M ( Q 1 , Q 3 ) was 46.0 (26.0, 65.0) lower than that in the control group, which was 60.0 (40.0, 77.0). The difference between the two groups was significant ( P <0.001). Compared with those in the Q 1 of CDGCI&#95;PW, the offspring in the Q 2 , Q 3, and Q 4 of CDGCI&#95;PW had a lower risk of total CHD ( OR =0.60, 95% CI : 0.43-0.83; OR =0.64, 95% CI : 0.45-0.89; OR =0.29, 95% CI : 0.19-0.44), with the trend test P <0.001. The risk of total CHD was reduced by 17% ( OR =0.83, 95% CI : 0.79-0.88) when 10 points increased the CDGCI&#95;PW score. The area under curve predicted by constructing the ROC curve was 0.793 (95% CI : 0.768-0.818), and at the maximum of the Youden index, the sensitivity was 0.740, and the specificity was 0.725. Conclusion: This study suggests that improving dietary quality during pregnancy may reduce the risk of CHD in offspring.

Isotemporal substitution model is a powerful tool to explore the real association between physical behavior and health outcomes, which has the potential of the application in large-scale cohort study. This paper systematically introduces the principle of isotemporal substitution model and its implementation method in specific analysis to provide analytical ideas for the epidemiological research related to physical behavior in China. The baseline data of Regional Ethic Cohort Study in Northwest China conducted in Shaanxi province were used to analyze the relationship between physical behavior and cardiovascular disease with single-factor model, partition model and isotemporal substitution model. The advantages and disadvantages of different models were compared, and the advantages of isotemporal substitution model in quantifying physical activity health risk were introduced. Isotemporal substitution model could qualify physical behavior and health outcomes, which has wide application value in epidemiological research.

In medical research, the quality of data is the key to success. Thus, data quality control becomes an important part of ensuring the research's high quality. REDCap system is an emerging data acquisition system in medical research, which is gradually applied in research at home and abroad. It is a hot issue to realize double data entry and data quality control in using the REDCap system, which researchers are concerned about when this system is supposed to apply. This article will systematically introduce how to use the REDCap system for double data entry and quality control from the aspects of research project creation, data collection tool design, double data entry, data checking and exporting.

Objective: This study explored the association between antenatal calcium supplementation in the childbearing aged women and risk of small for gestational age infant (SGA) among singleton in Shaanxi province,China. Methods: Multi-stage random cluster sampling method was employed to collect information about pregnant women, who were pregnant and had definite outcomes, and their infants, from 30 districts (counties) in 2010 to 2013. Information was collected by face-to-face questionnaire survey. Generalized linear mixed models were employed after adjusting covariates. Dependent variable was whether single-birth neonate was SGA, and independent variable was calcium supplementation of childbearing aged women in different pregnant periods. Results: A total of 28 357 childbearing aged women was recruited in this study. The age of these women was (28.08±4.74) years old, of which, 79.28% were rural residents and 60.90% had calcium supplementation intake. There was a number of 12 810 female in singleton neonates. The neonatal birth weight and gestational age were (3.27±0.16) kg and (277.44±8.80) day, respectively. The prevalence of SGA was 11.35% in total, and 10.48% in mothers with maternal calcium supplementation and 12.70% in mothers without maternal calcium supplementation in whole antenatal period. There were statistically significant differences seen in antenatal calcium supplementation within the subgroups of maternal age (whether the mother was an advanced maternal woman), residential area, maternal occupation, maternal parity, maternal education level, and household incomes ( P <0.05). After adjusting these covariates, the risk of SGA among childbearing aged women with antenatal calcium supplementation showed 16% decreased risk ( OR =0.84, 95% CI : 0.77-0.92). Further analysis of the different antenatal periods showed that calcium supplementation during the second and third trimester had a statistically significant difference in reducing the risk of neonatal SGA ( P <0.05). Besides, subgroup analysis showed that there was a statistically significant difference between the perinatal calcium supplementation and the single-born neonates with SGA Significance ( P <0.05) in non-advanced women, those who had a low education level and moderate household economic status groups. Conclusion: The risk reduction of SGA among singleton neonates is related to calcium supplementation during antenatal period in Shaanxi province.

Cohort study is one of the basic methods used in epidemiological research. With the development of the etiological analysis of complex diseases such as cardiovascular diseases, large natural population-based cohort study has become a popular topic in medical research. In the process of cohort development, one of the important issues is to ensure the efficiency and safety on data collection. As a database management system, with open source, free clinical research data collection and high quality, REDCap can widely be applied in large population-based cohort studies. This article summarizes the baseline survey and follow-up procedures on cohort studies and introduces a REDCap-system-based solution for data collection and management. Contents on the establishment of data working groups, data collection, cohort follow-up methods and field application are also discussed in this paper, in order to improve the efficiency of data collection and management in cohort study to help the development of cohort study in China.

Editor office’s response for Ahead of Print article withdrawn The article “Potential false-positive rate among the ‘asymptomatic infected individuals’ in close contacts of COVID-19 patients” was under strong discussion after pre-published. Questions from the readers mainly focused on the article’s results and conclusions were depended on theoretical deduction, but not the field epidemiology data and further researches were needed to prove the current theory. Based on previous discussions, the article was decided to be offline by the editorial board from the pre-publish lists. Objective: As the prevention and control of COVID-19continues to advance, the active nucleic acid test screening in the close contacts of the patients has been carrying out in many parts of China. However, the false-positive rate of positive results in the screening has not been reported up to now. But to clearify the false-positive rate during screening is important in COVID-19 control and prevention. Methods: Point values and reasonable ranges of the indicators which impact the false-positive rate of positive results were estimated based on the information available to us at present. The false-positive rate of positive results in the active screening was deduced, and univariate and multivariate-probabilistic sensitivity analyses were performed to understand the robustness of the findings. Results: When the infection rate of the close contacts and the sensitivity and specificity of reported results were taken as the point estimates, the positive predictive value of the active screening was only 19.67%, in contrast, the false-positive rate of positive results was 80.33%. The multivariate-probabilistic sensitivity analysis results supported the base-case findings, with a 75% probability for the false-positive rate of positive results over 47%. Conclusions: In the close contacts of COVID-19 patients, nearly half or even more of the 'asymptomatic infected individuals' reported in the active nucleic acid test screening might be false positives.

Objective: To explore the effect of maternal animal sourced food intake during pregnancy on neonate birth weight and provide scientific basis for guiding the reasonable diet intake in pregnant women and increasing neonate birth weight. Methods: Data were derived from a cross-sectional project of"the prevalence and risk factors of birth defects in Shaanxi province" , which were conducted in 30 counties in Shaanxi province from July to November in 2013. A stratified multistage random sampling method was used to select women who were pregnant between January 2010 and December 2013 for a random semi-quantitative food frequency questionnaire survey to collect the data on the frequency and amount of food consumption on animal protein sources and the data of newborns. Children aged 0-1 years and their mothers were selected as the study subjects. The generalized linear model was used to analyze the relationship between the neonate birth weight and maternal animal sourced food intake during pregnancy, and by using neonate birth weight as dependent variable, food intake frequency as independent variable, three adjustment models were established for stratified analysis. Results: Totally 11 459 participants were involved in this study. The average birth weight of newborn was (3 279.9±454.6) g, the average weekly intake of animal sourced foods was4.00 times for egg, 1.50 times for meat, 3.00 times for dairy foods, 0.50 times for fish and 5.00 times for overall animal sourced foods in pregnant women. Without stratification, three models shown that meat and overall animal sourced food intake had effects on neonate birth weight. After adjustment for gestational weeks, maternal age, social and demographic factors and others, meat intake increased by 1 time a week, the increase of neonate birth weight was about 5.26 (95 %CI : 1.32-9.20) g, and the overall animal food increased by 1 times a week, the average neonate birth weight increased by 3.24 (95 %CI : 1.09-5.39) g. Stratified analysis showed that meat and overall animal sourced food always had more influences on baby girls and those living in rural area. In the region classification, the overall animal sourced food intake had more influences on women living in northern area and Guanzhong area of Shaanxi, and meat intake had greater influence on women living in southern Shaanxi. And the influences were positive, the more animal sourced foods were taken, the greater the birth weight increased. Conclusion: Animal sourced food intake during pregnancy would benefit the increase of neonate birth weight. It suggests that pregnant women should pay more attention to the intake of animal sourced food.

Objective: To investigate the influencing factors on congenital malformation of body surface. Methods: Multi-stage stratified random sampling method was adopted. A questionnaire survey was conducted among the childbearing aged women who experienced more than 28 weeks pregnancy or having definite pregnancy outcomes in Shaanxi, during 2010-2013. Results: Results from the logistic regression model showed that factors as: intrahepatic cholestasis of pregnancy ( OR =21.76, 95 %CI : 4.46-106.25), histories with abnormal pregnancy or reproduction ( OR =11.88, 95 %CI : 9.14-15.45), having birth defects in the family ( OR =6.15, 95 %CI : 2.66-14.23), being twins ( OR =5.74, 95 % CI : 3.34-9.86), being worker (compared with others, OR =2.47, 95 % CI : 1.30-4.68) or farmer (compared with others, OR =1.91, 95 %CI : 1.14-3.20), less than 4 times of antenatal care (compared with >7, OR =1.84, 95 % CI : 1.28-2.64), occupational exposure to related risks during pregnancy ( OR =1.74, 95 % CI : 1.26-2.42), mother's hometown was from mid-part of Shaanxi (compared with northern Shaanxi, OR =1.65, 95 %CI : 1.20-2.28), mother's native residence was from the rural areas ( OR =1.75, 95 % CI : 1.13-2.71), drug use ( OR =1.64, 95 % CI : 1.26-2.13) etc . were risk factors for congenital malformation of body surface. Iron supplement during pregnancy ( OR =0.46, 95 %CI : 0.21-0.99) appeared as protective factor for congenital malformation of body surface. Conclusion: The following factors seemed to be of risk for congenital malformation of body surface, including: mother's native area was from the middle part of Shaanxi and living in rural area, being worker or farmer, histories of abnormal pregnancy and reproduction, history of birth defects in the family, being twins, with antenatal care less than 4 times, occupational exposure to dangerous materials, drug use, intrahepatic cholestasis during pregnancy etc .

Objective: To explore the ethnic differences on nutritional status of children under three years old, in the western areas of China and to identify the affecting factors., Methods: 14 072 children under the age of three years and their mothers were recruited, using the proportion population sampling method in 45 counties in the western areas of China. Height and weight were used as the measurement on nutrition of children., Results: Height and weight of children with Han, Uyghur, Tibetan and Zhuang ethnicities were all lower than the WHO standards and with differences on height and weight among them. There were also ethnic differences on the status of malnutrition. Prevalence rates of stunting were 14.7%, 20.3%, 26.9% and 26.5% for Han, Uyghur, Tibetan and Zhuang ethnicities, respectively. Prevalence rates of underweight were 6.1%, 10.7%, 6.8% and 15.5% among the Han, Uyghur, Tibetan and Zhuang ethnicities, respectively. The prevalence rates of wasting were 4.2%, 5.3%, 2.9%, 8.9%, and of under nutrition were 19.2%, 25.5%, 30.3% and 36.5% for the Han, the Uyghur, the Tibetan and the Zhuang ethnicities, respectively. When factors as family size, years of schooling of parents, family numbers, sex, age (months), mother's height and weight, ways of feeding and sources of family income etc. were adjusted, children with Uyghur, Tibetan, Zhuang and other ethnicities were still presented more malnutrition than the children with Han ethnicity., Conclusion: There were differences on malnutrition status of children under the age of three years among the studies on different ethnicities. Undernutrition was less than nutritional status, seen in children of the Han nationality than other minority ethnicities. Ethnicity seemed to be related to differences in the nutritional status of children in western China while children of the Han nationality would be better than other minorities on nutritional status if they were in same living conditional.

Objective: To investigate the current status of unintentional injuries among rural children aged 0 - 12 years in Shaanxi., Methods: Using a three-stage stratified random sampling method to study the status of unintentional injuries among 4668 children aged 0 - 12 years old during the period of 2010 in rural areas of Shaanxi province., Results: The overall incidence of injure was 27.3%, with boys as 28.7% and girls as 25.6% respectively (χ(2) = 5.91, P = 0.015). Age differences in unintentional injuries rate were also significant (χ(2) = 9.91, P = 0.007), with children under 0 - 3 years old having the highest rate of injuries, followed by 7 - 12 and 4 - 6 year-olds. Falls took the leading type of accident among both sexes and all age groups. Poorer the family economic situation was, higher the incidence of unintentional injuries appeared., Conclusion: Falls was the leading cause of unintentional injuries among rural children in Shaanxi province, with age 0 - 3 year group appeared the highest to suffer unintentional injuries. Unintentional injuries were associated with the economic status of the families.

Objective: To study the current status and risk factors of spontaneous abortion of women at reproductive age in rural areas of Shaanxi province., Methods: Pregnant women who lived in Changwu and Bin counties of Shaanxi province were interviewed on their former reproductive history and being followed on the outcomes of pregnancy from 2002 to 2005., Results: There were 5844 pregnant women under study with a total number of 9638 pregnancies including 1153 spontaneous abortive episodes. Among the pregnant women in rural areas of Shaanxi province, the ratio between spontaneous abortion and pregnancies was 12.0% and the spontaneous abortion rate(SAR) was 13.6%. Ratio between the number of women who had experienced spontaneous abortion and the total number of women under survey was 16.4 %. The risks of having spontaneous abortion would increase among women who were aged > or =30 years and those with more than 3 pregnancies., Conclusion: To reduce the incidence of spontaneous abortion among rural area women, the approaches should include: strengthening the family planning management, reducing of the frequency of pregnancy, extending the pregnancy interval and avoiding advanced ageing pregnancies.

Objective: To study the status of spontaneous abortion among reproductive Tibetan women aged 15 - 49 years., Methods: A cross-sectional survey was conducted on reproductive history of Tibetan women and the sample was chosen under the stratified multistage cluster random sampling technique., Results: A total number of 3741 women were studied with a total number of 10,245 pregnancies. There were 386 spontaneous abortions reported with an incidence rate of 3.9%. Women living in the urban area had a higher rate than living in the rural areas. Women living in area where altitudes were above 4500 m, had a 2-time risk of having spontaneous abortion than those living in areas below 3500 m. The risk of having spontaneous abortion increased among women aged > or = 35 and those with more than 3 pregnancies., Conclusions: High altitude could contribute to the increase of spontaneous abortions incidence, suggesting that improvement of maternal care and nutrition and reduction of the frequency of pregnancy had important roles to play in reducing the incidence of spontaneous abortion among Tibetan women. Despite the fact that retrospective study on reproductive history could underestimate the incidence of spontaneous abortion, the incidence rate among Tibetan women might not be much higher than women living in the lowland areas.

Objective: To assess nutritional status among children younger than 3 years in 40 counties of western China, using anthropometry., Methods: With cross-sectional study and random sampling, a survey with a sample size of 7252 was conducted in 40 counties of western China on children under 3 years old. Height and weight were measured and nutrition status was evaluated with WHO/NCHS reference using Z scores., Results: SD of height for age (HA) and weight for age (WA) were 1.10 - 1.30 and 1.06 - 1.40, respectively and SD of WAZ for infants varied. The distribution of HA Z and WAZ shifted downward to 1 unit and 0.4 unit for distribution of weight for height (WHZ). The prevalence of stunting, underweight and wasting were 23.0%, 22.6% and 7.5% respectively. The prevalence rates were low among those yourger than 3 months. Stunting and underweight increased sharply after 6 months and reached 20% - 30%. Significant correlation was found between underweight and stunting or wasting with coefficients of 0.815 and 0.636, respectively. No correlation was found between stunting and wasting., Conclusion: The nutrition status adversely affected children as a whole but not only for individuals. There was a higher prevalence of malnutrition mainly on low height to children. Weight for age must be interpreted cautiously because of the inability of this indicator in distinguishing stunting and wasting just by itself. Assessment by anthropometry called for accurate information on age and measurement of height and weight.

Objective: To understand the prevalence of anemia in children living in poor rural villages in western China and to find out related factors affecting hemoglobin level of children so as to search for proper intervention., Methods: 3747 children under 3 years old and their families were studied using stratified random sampling in 40 counties in western China. Databases were set up, and data logically checked by Epi 6.0 software. All the data were input with duplication method and analyzed by SPSS 10.0 software., Results: The prevalence of anemia of children under 3-year-old was 32.7% in 40 counties with significant difference among provinces with the highest in Guizhou province (43.5%). The lowest was in Ningxia and Qinghai provinces, which was 20%. The prevalence of anemia of children was relatively high in 6 and 18 months of age after birth, but declining when children grew older. Many factors were associated with children's anemia, viz. feeding pattern, age, diarrhea, family income, nationality, mother with anemia and drinking clean water etc., Conclusion: Interventions as popularizing knowledge of appropriate feeding, drinking clean water and decreasing the prevalence of common diseases including diarrhea would decrease the prevalence of anemia of local children.

Objective: To understand the feeding status of Tibetan children aged below three years old., Methods: Cross-sectional study and randomly sampling were used. The information on complementary food was obtained through the recollection from mother of the child. Data of complementary food of Tibet children was compared with those of the children from the surveys of nine cities in China and 40 poor counties in western China., Results: One thousand six hundred and fifty-five children were studied. The findings indicated that the age of introduction of Zanba (a kind food of mixture of highland barley flour and butter) was 1.98 months after birth and the age of introduction of egg and meat was about 8 - 9 months. Boys were fed with Zanba earlier than girls but there was no significant difference in the introduction of other complementary food between sexes. Urban children were introduced with complementary food earlier than rural children, and children in the agricultural region earlier than those in the pasturing region. The proportion of no introduction of any complementary food by the age of 4 months was about 10.6% for urban children, but 21.7% for rural children while 14.2% for children in the agricultural region and 30.9% for children in the pasturing region. The proportion of no introduction of complementary food was 11.5% for Tibetan children compared with 45.2% for the children of 40 poor counties in western China. The proportions of introduction of the following complementary foods were 89.1% for Zanba, 22.1% for egg, 29.1% for fresh milk, 23.5% for meat, 17.5% for vegetable, 0.75% for bean products, 1.03% for fish and 3.35% for chicken respectively., Conclusions: The main complementary foods for Tibetan children included Zanba, milk, mutton and beef. There was a small amount of vegetable in diet. The introduction of bean, chicken and fish was not common. Early and monotony seemed to be the character of introduction of complementary food for Tibetan children. Improving introduction of complementary food is important in enhancing the nutritional status of Tibetan children.