[The evaluation of dietary salt and potassium intake assessed by two 24-hour urine specimens among 284 primary and secondary school students].

To estimate the dietary salt and potassium intake by two 24 hour urine salt and potassium excretion in primary and secondary school students. The boarders from Grade 5 to 6 in a rural primary school and Grade 1 to 3 in a rural middle school in Changde City, Hunan Province were recruited from October to December in 2017. Subjects who had 2 and more urinary incontinence episodes or a history of kidney disease or diarrhea and girls in menstruation were excluded. The final analysis included 284 subjects. Questionnaires on basic demographic information were collected, and height and weight were examined. Two inconsecutive 24-hour urine specimens were collected in weekdays. The differences and consistency between two 24-hour urine were tested and dietary salt and potassium intake were assessed by the average of two 24-hour urine collections. A Total of 284 participants was (12.1±1.5) years old, of which 148 (52.1%) were boys and 36 (12.7%) were overweight. In the first 24-hour urine, the volume [(50) ((25), (75))=670 (513, 868) ml], potassium concentration [(50) ((25), (75))=29 (21, 39) mmol/L] and potassium excretion [(50) ((25), (75))=0.7 (0.6, 1.0) g] were similar to those in the second 24-hour urine [(5)0 ((25), (75)) values were 660 (490, 916) ml, 30 (21,40) mmol/L, and 0.8 (0.6, 1.0) g, respectively]. But the sodium and creatinine concentrations, salt excretion in the first 24-hour urine [(50) ((25), (75)) values were 175 (123, 219) mmol/L, 7.20 (5.15, 10.86) mmol/L and 6.6 (5.0, 8.7) g, respectively] were lower than those in the second 24-hour urine [(50) ((25), (75)) values were 188 (133, 248) mmol/L, 8.66 (5.99, 12.47) mmol/L and 7.3 (5.2, 9.2) g, respectively] (all values<0.05). The intraclass correlation coefficients between salt and potassium excretions in the two 24-hour urine were 0.534 (95: 0.412-0.631) and 0.478 (95: 0.341-0.587) (0.001), respectively. The mean± of salt consumed was (7.3±2.5) g (range: 2.3 to 18.8 g) per day by all participants. Overweight children consumed more salt [(8.2±2.6) g/d] than those non-overweight [(7.2±2.4) g/d] (0.05). The mean± of potassium consumed was (1.1±0.3) g (range: 0.4 to 2.3 g) per day. Boys consumed more potassium [(1.1±0.3) g/d] than girls [(1.0±0.3) g/d] (0.05), and overweight children had higher potassium intake [(1.2±0.3) g/d] than those non-overweight [(1.0±0.3) g/d] (0.05). A total of 212 participants (74.6%) consumed more salt than the recommended level and all participants had inadequate potassium intake. The problem of excessive salt intake and insufficient potassium intake of rural primary and middle school students was serious.