Questions were raised about the overall layout of the instrument; many parents (as well as patients) thought that having frequency and severity of particular items side by side, rather than on two separate pages, would facilitate measuring each symptom comprehensively.
The DUQOL shows the lowest range of severity of items.
In health status assessments, person measures indicate the health of persons, and item measures indicate the severity of items.
It can be seen in Fig. 3 that the range of severity of items is greater in the HRQoLDA in comparison with the WHOQOL-BREF and the DUQOL.
The map of persons and items (Fig. 3) shows the combined position of the HRQoLDA, the DUQOL and the WHOQOL-BREF severity of items on the HRQoL continuum (right side).
Item calibrations indicate the relative severity of an item because items with lower calibrations are affirmed by subjects with lesser degrees of food insecurity than items with high calibrations [ 13, 14].
Thus item 1 correlated with the severity of SCL items 1,7,8 and 15; item 2 correlated with SCL items 1, 7, 8, 11, 15; item 4 correlated with SCL items 1, 7, 8, 11, 13 and 16; item 5 correlated with SCL items 1, 2, 3, 6, 7, 9, 10, 11 and 13; item 6 correlated with SCL items 1, 2, 3, 7, 8, 11, 13 and 15; and item 7 correlated with SCL items 1, 2, 6, 8 and 10.
In the one-parameter logistic model, the probability of a subject, s, giving an affirmative response to item i is estimated from the difference between the item calibration or relative severity of the item, β i, and the trait level or severity of experienced food insecurity of the subject, θs.
The slope index of income-related inequality also increased as the proposed severity of each item increased although estimates were imprecise for the low prevalence items.
This process also provided estimates of the severity of each item calculated as logits, which made it possible to compare CAT scores and SGRQ items using the same metric.
