Food and portion reporting was made easier by the use of a validated reference book showing various portions of the common food and beverage choices (Suvimax, 2000).
Furthermore, the use of multiple validated reference genes, rather than a single gene, improved the normalization of the RNA concentration across all samples.
Increasing stringency by controlling primers for cDNA synthesis, designing intron-spanning primers for amplification and the use of alternative validated reference genes during the analysis appears to reduce the number of significant genes at 24 h.
Finally, there are challenges in analyzing the data which include the lack of validated references and suitable validated interpretation tools.
Further studies are required to assess both the clinical utility and validity of the depression and somatization subscales of RDC/TMD Axis II using previously validated reference standards [13, 14].
If inappropriate reference genes are used for normalization, the experimental results obtained can differ greatly from those using a validated reference gene.
Quality measurements depend on the use of validated methods, determination of the measurement uncertainty, and the availability of reference materials as well as components including appropriate calibrated equipment, trained operators, quality reagents, and the quality of the extracted DNA.
The validation of known metabolites does not include the use of authentic reference standards, but instead relies on previously described compounds for Arabidopsis, the use of validated fragmentation patterns, and mass shifts of 13C, 15N, and 34S isotope labeled Arabidopsis thaliana samples (Giavalisco et al., submitted).
Strengths of the study are the large and unselected population and the use of validated diagnoses.
Another strength is the use of validated questionnaires that were published prior to the study.
