Salt sales survey: a simplified, cost-effective method to evaluate population salt reduction programs--a cluster-randomized trial.

Twenty-four-hour urine collection, as a gold standard method of measuring salt intake, is costly and resource consuming, which limits its use in monitoring population salt reduction programs. Our study aimed to determine whether a salt sales survey could serve as an alternative method. This was a substudy of China Rural Health Initiative-Sodium Reduction Study (CRHI-SRS), in which 120 villages were randomly allocated (1:1:2) into a price subsidy+health education (PS+HE) group, a HE-only group or a control group. Salt substitutes (SS) were supplied to shops in the intervention groups; 24-h urine was collected from 2567 randomly selected adults at the end of the trial to evaluate the effects of the intervention. Ten villages were randomly selected from each group (that is, 30 villages in total), and 166 shops from these villages were invited to participate in the monthly salt sales survey. The results showed that during the intervention period, mean monthly sales of SS per shop were 38.0 kg for the PS+HE group, 19.2 kg for the HE only and 2.2 kg for the control group (P<0.05), which was consistent with the results from the 24-h urine sodium and potassium data. The intervention effects of CRHI-SRS on sodium and potassium intake estimated from SS sales were 101% and 114%, respectively, of those observed from the 24-h urine data. Furthermore, the salt sales survey cost only 14% of the cost of the 24-h urine method and had greater statistical power. The results indicate that a salt sales survey could serve as a simple, sensitive and cost-effective method to evaluate community-based salt reduction programs in which salt is mainly added by the consumers.