Table 2.

Type of calibration study with typical design and information to be extracted

Type of calibration study	Typical design	Relevant information to extract
Reliability study	• Employs a comparison of several instruments to estimate dietary intake one of which may be a "gold-standard" • Uses a sub-sample of subjects from the main study or an external sample	• Number of instruments used • Number of subjects • Were biochemical markers used? • Was the sub-sample from main study or an external sample?
Validation study	• Employs a "gold-standard" compared with another instrument used to estimate dietary intake • Uses a sub-sample of subjects from the main study or an external sample	• Number of instruments used • Number of subjects • What was the "gold-standard" (biochemical marker/other instrument)? • Was the sub-sample from main study or an external sample?
Reproducibility study	• Employs replicate measurements for an instrument used to estimate dietary intake • Uses a sub-sample of subjects from the main study or an external sample	• Instrument used • Number of subjects • Number of repeat measures used, • Spacing of repeat measures, • Were biochemical markers used? • Was the sub-sample from main study or an external sample?