Objective:To analyze the external quality control assessment results of fluoride testing laboratories in endemic disease prevention and control institutions nationwide from 2006 to 2023, investigate the quality control capabilities of these laboratories in various provinces, prefectures, cities, and counties nationwide, and ensure the accuracy and reliability of surveillance data on endemic fluorosis nationwide.Methods:Using retrospective analysis, the external quality control assessment results of all participating fluoride testing laboratories of national endemic disease prevention and control institutions from 2006 to 2023 were summarized and analyzed. The assessment results from 2006 to 2008 were tested for outliers using Grubbs method, homogeneity of variance using Cochran method, excluding the assessment data of unqualified laboratories, calculating the total mean and total standard deviation, Z-score method was used to test the assessment of laboratories, and statistical analysis and judgment were done when the result of │Z│ < 3. The assessment results from 2009 - 2023 were obtained from all laboratories. In 2010, two tests were conducted in the first and second half of the year, and the Z-ratio scores of each laboratory were calculated using robust statistics. When │Z│≤2, the assessment was qualified; when 2 < │Z│ < 3, the assessment was basically qualified; when│Z│≥3, the assessment was unqualified, and the consensus value came from all participating laboratories in the assessment.Results:From the beginning of quality control operation in 2006 to 2023, the number of laboratories participated in external quality control assessments had significantly increased. The number of laboratories participated in water fluoride assessment increased from 30 in 2006 to 1 277 in 2023, and the number of laboratories participated in urine fluoride assessment increased from 29 to 497. The number of laboratories participated in the brick tea fluorine assessment had increased from 43 in 2014 to 193 in 2023. The assessment results showed that when │Z│ < 3, the total qualified rate of fluoride external quality control in fluoride testing laboratories of national endemic disease control institutions was 95.2%, with the lowest being 87.1% (27/31) in 2008 and the highest being 100.0% (394/394) in 2014. When │Z│≤2, the total feedback pass rate was 88.4%, with the lowest being 79.3% (288/363) in the first half of 2010 and the highest being 99.5% (392/394) in 2014. The assessment results showed that when │Z│ < 3, the total pass rate of urine fluoride external quality control in fluoride testing laboratories of national endemic disease control institutions was 98.0%, with the lowest being 86.2% (25/29) in 2006 and 2007, respectively, and the highest being 100.0% (68/68) in 2014. When │Z│≤2, the total qualification rate was 93.7%, with the lowest being 86.5% (64/74) in the second half of 2010 and the highest being 100.0% (68/68) in 2014. The assessment results showed that when│Z│ < 3, the total pass rate of extra-fluoride quality control of brick tea in fluoride testing laboratories of national endemic disease control institutions was 95.4%, with the lowest being 85.0% (164/193) in 2023, and the highest being 100.0% (43/43, 51/51, 79/79) in 2014, 2015 and 2016, respectively. When │Z│≤2, the total pass rate was 89.2%, with the lowest being 72.7% (32/44) in 2017 and the highest being 100.0% (43/43) in 2014. From 2009 to 2023, there were a total of 21 provincial-level laboratories that passed the water fluoride detection assessment, including 3 provinces where all prefecture level and county-level laboratories were qualified. The assessment results of urinary fluorine showed that there were 11 qualified provincial-level laboratories and 1 prefecture-level laboratory. From 2014 to 2023, the assessment results of brick-tea fluorine showed that there were 5 provincial-level laboratories that passed the tea fluorine testing assessment and no prefecture-level laboratory.Conclusions:Conclusion: From 2006 to 2023, the number of fluoride testing laboratories participating in external quality control assessment has increased year by year, and most provincial, municipal and county-level laboratories have good fluoride testing capabilities, which can meet the testing needs of endemic disease prevention and monitoring. For some laboratories with problems, targeted rectification should be carried out to improve the quality of detection, in order to provide better technical support for the monitoring of endemic fluorosis areas.

Objective:To study and establish a high-throughput and rapid detection method for fluorine ion content in water based on 96-well plate and microplate reader, and to evaluate its performance.Methods:According to the principle of blue ternary complex formed by reaction of fluorine ion with fluorine reagent and lanthanum nitrate, the absorbance of the complex at the wavelength of 650 nm was proportional to the concentration of fluoride ion, and the content of fluoride ion in water samples was quantitatively determined by microplate reader. The accuracy, precision and detection limit of the method were evaluated by the standard recovery rate method and the reference material method.Results:The linear correlation coefficient of the standard curve of this method was > 0.999; the standard recovery rates of different concentrations were 99.00% - 103.33% in the accuracy experiment of this method, and the average recovery rate was 101.08%. In the standard material method, the measured values are all within the calibration range of the standard solution. The relative standard deviation of water samples with different concentrations was ≤10% in the precision experiment and the detection limit was 0.06 mg/L.Conclusion:The method has good accuracy and precision, low detection limit and small sample consumption, and this method can greatly improve the detection efficiency.

Objective:To analyze the relationship between dietary composition of residents in endemic fluorosis areas and skeletal fluorosis.Methods:A case-control study was used to analyze the difference of dietary composition between patients with skeletal fluorosis (case group) and residents without skeletal fluorosis (control group). In August 2019, taking the drinking water-borne endemic fluorosis area in Wenshui County, Lvliang City, Shanxi Province as the survey site, a cluster sampling method was adopted to select local residents aged over 18 years old, and a questionnaire survey was conducted by face-to-face interview. The survey contents included gender, age and consumption frequency of various foods. Binary logistic regression was used to analyze the relationship between food consumption frequency and skeletal fluorosis. The diagnosis of skeletal fluorosis was made by using portable digital radiography (DR) to take X-ray films of forearm and lower leg, combining with clinical signs, and according to the Diagnostic Standard for Endemic Skeletal Fluorosis (WS/T 192-2008) to determine.Results:A total of 1 061 subjects were included in this study, including 376 in the case group and 685 in the control group. The age composition of patients in the case group (≤60, > 60 years old: 162, 214 cases) was significantly different from that in the control group (≤60, > 60 years old: 423, 261 cases, χ 2 = 34.52, P < 0.001). There was no statistically significant difference in gender ratio (χ 2 = 1.37, P = 0.251). The proportion of patients in the case group who ate meat and eggs > 1 time/week was lower than that in the control group (χ 2 = 8.06, 5.46, P < 0.05), the proportion of patients who ate milk > 1 time/week was higher than that in the control group (χ 2 = 4.01, P = 0.046), and the proportion of patients who ate seafood ≥1 time/week was lower than that in the control group (χ 2 = 4.16, P = 0.046). The results of binary logistic regression analysis showed that after adjusting for age, sex, and urinary fluoride, the frequency of eating meat, eggs or milk > 1 time/week and the frequency of eating seafood ≥1 time/week were not related to the risk of skeletal fluorosis ( P > 0.05); however, in the group ≤60 years old, the frequency of eating eggs > 1 time/week was associated with the risk of skeletal fluorosis [odds ratio ( OR) = 0.59, 95% confidence interval ( CI): 0.39, 0.88]. Conclusions:The consumption frequency of meat, milk, eggs and seafood is significantly different between the skeletal fluorosis patients and the control people. In the population ≤60 years old, consumption frequency of eggs > 1 time/week may reduce the risk of skeletal fluorosis.