Abstract:
The “Dairy Diary” is a user-friendly web-based dairy intake screener. The reliability
and validity are unknown. We aimed to evaluate the screener in terms of test–retest
reliability and comparative validity. In a diagnostic accuracy study, a purposefully recruited sample of 79 (age: 21.6 ± 3.8 years) undergraduate dietetics/nutrition students
from three South African universities completed 3 non-consecutive days of weighed
food records (reference standard) within a seven-day period (comparative validity),
followed by two administrations, 2 weeks apart, of the screener (index test) (reliability). For the four dairy product serving scores (PSSs) and the summative dairy serving
scores (DSSs) of the screener and the food records, t-tests, correlations, Bland–
Altman, Kappa, McNemar's, and diagnostic accuracy were determined. For reliability,
mean PSSs and DSSs did not differ significantly (p> .05) between the screener administrations. The mean PSSs were strongly correlated: milk (r= .69; p< .001), maas (fermented milk) (r= .72; p< .001), yoghurt (r= .71; p< .001), cheese (r= .74; p< .001). For
DSSs, Kappa was moderate (k= 0.45; p< .001). Non-agreeing responses suggest symmetry (p= .334). For validity, the PSSs of the screener and food records were moderately correlated [milk (r= .30; p= .0129), yoghurt (r= .38; p< .001), cheese (r= .38;
p< .001)], with k= 0.31 (p= .006) for DSS. Bland–Altman analyses showed acceptable
agreement for DSSs (bias: −0.49; 95% CI: −0.7 to −0.3). Categorized DSSs had high
sensitivity (81.4%) and positive predictive value (93.4%), yet low specificity (55.6%)
and negative predictive value (27.8%). The area under the receiver operating characteristic curve (0.7) was acceptable. The “Dairy Diary” is test–retest reliable with moderate comparative validity to screen for dairy intake of nutrition-literate consumers.
