We assessed the validity of a recently developed dish composition database (DCD) against urinary biomarkers compared with a standard food composition database (FCD).

Intakes of protein, Na and K were estimated by 2 × 24 h urine collections and by 4 d dietary record data based on the DCD (including 128 dishes) or FCD (including 1878 foods).

Japan.

A total of 161 men and 163 women aged 20–69 years.

Compared with the 24 h urine-based estimates, the median intakes estimated using the DCD and FCD differed significantly for protein and Na in men and for Na and K in women. Deattenuated Spearman correlation coefficients using 24 h urine-based estimates for the intakes of protein, Na and K were lower in the DCD (respectively: 0·26, 0·15 and 0·44 in men; 0·22, 0·27 and 0·22 in women) than those in the FCD (respectively: 0·43, 0·40 and 0·59 in men; 0·33, 0·45 and 0·42 in women). When data on dish portion size reported by participants were used for estimation instead of standard portion-size data based on the DCD, the accuracy of the estimated median intakes did not change notably, whereas the deattenuated correlation coefficients improved (for protein, Na and K respectively: 0·32, 0·31 and 0·56 in men; 0·31, 0·41 and 0·39 in women).

The DCD supported by individual-level information on dish portion size showed fair to moderate validity in ranking individuals according to their intakes of protein, Na and K, similar to the FCD.

Measurement of mean population Na and K intakes typically uses laboratory-based assays, which can add significant logistical burden and costs. A valid field-based measurement method would be a significant advance. In the current study, we used 24 h urine samples to compare estimates of Na, K and Na:K ratio based upon assays done using the field-based Horiba twin meter v. laboratory-based methods.

The performance of the Horiba twin meter was determined by comparing field-based estimates of mean Na and K against those obtained using laboratory-based methods. The reported 95 % limits of agreement of Bland–Altman plots were calculated based on a regression approach for non-uniform differences.

The 24 h urine samples were collected as part of an ongoing study being done in rural China.

One hundred and sixty-six complete 24 h urine samples were qualified for estimating 24 h urinary Na and K excretion.

Mean Na and K excretion were estimated as 170·4 and 37·4 mmol/d, respectively, using the meter-based assays; and 193·4 and 43·8 mmol/d, respectively, using the laboratory-based assays. There was excellent relative reliability (intraclass correlation coefficient) for both Na (0·986) and K (0·986). Bland–Altman plots showed moderate-to-good agreement between the two methods.

Na and K intake estimations were moderately underestimated using assays based upon the Horiba twin meter. Compared with standard laboratory-based methods, the portable device was more practical and convenient.