Validation of the smartphone-based dietary assessment tool "Traqq" for assessing actual dietary intake by repeated 2-h recalls in adults: comparison with 24-h recalls and urinary biomarkers.

Background: Conventional dietary assessment methods are affected by measurement errors. We developed a smartphone-based 2-h recall (2hR) methodology to reduce participant burden and memory-related bias.

Objective: Assessing the validity of the 2hR method against traditional 24-h recalls (24hRs) and objective biomarkers.

Methods: Dietary intake was assessed in 215 Dutch adults on 6 randomly selected nonconsecutive days (i.e., 3 2hR-days and 3 24hRs) during a 4-wk period. Sixty-three participants provided 4 24-h urine samples, to assess urinary nitrogen and potassium concentrations.

Results: Intake estimates of energy (2052±503 kcal vs. 1976±483 kcal) and nutrients (e.g., protein: 78±23 g vs. 71±19 g; fat: 84±30 g vs. 79±26 g; carbohydrates: 220±60 g vs. 216±60 g) were slightly higher with 2hR-days than with 24hRs. Comparing self-reported protein and potassium intake to urinary nitrogen and potassium concentrations indicated a slightly higher accuracy of 2hR-days than 24hRs (protein: -14% vs. -18%; potassium: -11% vs. -16%). Correlation coefficients between methods ranged from 0.41 to 0.75 for energy and macronutrients and from 0.41 to 0.62 for micronutrients. Generally, regularly consumed food groups showed small differences in intake (<10%) and good correlations (>0.60). Intake of energy, nutrients, and food groups showed similar reproducibility (intraclass correlation coefficient) for 2hR-days and 24hRs.

Conclusions: Comparing 2hR-days with 24hRs showed a relatively similar group-level bias for energy, most nutrients, and food groups. Differences were mostly due to higher intake estimates by 2hR-days. Biomarker comparisons showed less underestimation by 2hR-days as compared with 24hRs, suggesting that 2hR-days are a valid approach to assess the intake of energy, nutrients, and food groups. This trial was registered at the Dutch Central Committee on Research Involving Human Subjects (CCMO) registry as ABR. No. NL69065.081.19.