Internal structure and domain-total score correlation
Validity is a measure that describes to what extend a scale measures what it intends to measure. The currently available information, however, can be only regarded as a good starting point of the validation process in the long run.
The first step of validation was to multivariately demonstrate the internal structure (“dimensions”) of a new scale through factor analysis. The five domains do fit our conceptional expectations and seem to be biologically plausible. Moreover, it was successfully confirmed in an independent population sample in German as described above (see “internal structure of the scale”).
A further aspect of structural validity is the domain and total score correlation. The correlations of the total score with the five domains scores should be high, whereas the correlations among the individual domains should be smaller, because the subscales are supposed to be “independent” according the factor-analytic model we used.
The correlations of the five domains with the total scale ranged from r= 0.44 to r= 0.71 and the correlations among subscales oscillated in the majority around or lower than r= 0.3. In the independent German validation survey, the “domain score – total score correlations” were slightly higher. The correlation with the total score was 0.64, 0.61, 0.68, 0.67, and 0.56 for the domains PSYH, HORM, MENS, SEX, and ABDOM, respectively.
As expected, the correlations among domains were smaller, i.e. ranging well under 0.4 in the normative Italian sample. This was later confirmed in the German validation study with a tendency toward even lower correlations among domains.
Altogether, the SHE scale depicts favorable psychometric characteristics taking the domain-total score correlations together with the item-domain, and item-total correlations.
Concurrent validity with other scales
To get information about the concurrent validity of the SHE scale and its domains, we compared the SHE scale with other established (validated) scales within a small Italian survey (n=47), and a population-based German survey (n=108).
Since the SHE scale was designed also as health-related QoL scale with specific focus on short-term hormonal effects, we were particularly interested in evidence that the SHE scale really measures quality of life: The SHE total score significantly correlated with the generic QoL scale SF-12 (total, physical, and mental health score) in the German survey and similarly in the Austrian sample. However, the correlation coefficients were not high, i.e. ranging between r=0.3 and r=08)
Other significant correlations were observed between domains of the SHE-scale and the domain anxiety of the HADS as well as with the domain ‘psychosomatic QoL’ of the QSF in the German survey (correlation coefficients ranging between r=0.3 and r=0.6) .
Inverse correlations are explained by different directions of the scores, i.e. in one scale the scores increase with better perceived health (e.g. SF-12) and others with increasing complaints (e.g. SHE, QSF).
The psychological domain of the SHE scale showed – as the total score – significant association with mental health and total score (SF-12), anxiety (HADS), and psychosomatic QoL (QSF) (range r=0.3 to r=0.6). The hormone-related domain showed correlations with SF-12 as well as QSF (range r=0.4 to r=0.5). The highest correlation of the abdominal domain of SHE was observed at least in the German sample with SF-12 (total and physical health domain) (r=0.6). The menstrual domain showed only a weak correlation with SF-12 and the self-assessment of sexual dysfunction (QSF scale) (r=0.3). The sexual domain score was correlated with anxiety (HADS) and with psychological QoL (QSF) (range r=0.3 to r=0.4).
No meaningful association of the SHE sexual score was observed with the sexual domain of the QSF scale. Data on low sexual desire, arousal, and satisfaction recorded by the FSEP were only weakly correlated with the score of the sexual domain of the SHE scale. And an inverse correlation was observed between degree of sexual arousal (excitement) and higher scores of the sexual SHE domain (the direction of the scores is inverse in the scales).
Altogether, the SHE scale with its total and domain scores seem to be valid, although not all information about the validity is available yet.
Ability to detect changes
Since the SHE scale was not yet applied in treatment-related observational or the randomized clinical studies, there are no data to describe responsiveness or MID.