Reference outlining the method | Classical measurement error model assumed | Requirements of calibration study | Relationship between reference instrument and dietary instrument of interest. | Aim of the approach |
---|---|---|---|---|
Method of Triads [105] | Yes | Three methods of assessment of dietary intake to be available (e.g. FFQ, 24-h dietary recalls and a biomarker) | The minimal statistical requirements are that the measurements from the three instruments are linearly related to the true intake levels and their random errors are statistically independent (i.e. uncorrelated). | To assess the ‘relative validity’ of dietary intake when the quantitative information was available for three methods (usually FFQ, 24-h dietary recalls and a biomarker). |
Method of Triads Extension 1(MOTEX1) [2004] [27] | No | Superior or gold standard reference instrument available | The correlation between errors in the dietary instrument of interest and reference instrument can be non-zero (i.e. the errors are not statistically independent). | Aim to estimate the magnitude of correlations between errors in reference and the dietary instrument of interest (e.g. a FFQ). |
Method of Triads Extension 2 (MOTEX2) [2005] [36] | No | Multiple dietary assessment methods required (e.g. self-reported instruments and biomarkers). | Three surrogate variables questionnaire (Q); M, and P where M and P are both instrumental (often biological) variables. No conventional reference instrument is required. M and P can be concentration biomarkers rather than recovery biomarkers. | To estimate the correlation between a dietary instrument of interest (Q) and true intake (T). |
Method of Triads Extension 3 (MOTEX3) [2007] [35] | No | Multiple dietary assessment methods required (e.g. self-reported instruments and biomarkers). | No conventional reference instrument is required. Requires that error correlations between dietary estimates and biomarkers or between biomarkers be close to zero. M, and P are biomarkers with M being a direct measure of dietary intake and M and P are chose so that one has a long half-life and the other a short half-life. | Aimed to produce corrected estimates of the effects on an outcome variable of changing the true exposure variables by one standard deviation, a standardized regression calibration. |