PurposeNew patient reported outcome (PRO) measures are regularly developed to assess various aspects of the patients’ perspective on their disease and treatment. For these instruments to be useful in clinical research, they must undergo a proper psychometric validation, including demonstration of cross-sectional and longitudinal measurement properties. This quantitative evaluation requires a study to be conducted on an appropriate sample size. The aim of this research was to list and describe practices in PRO and proxy PRO primary psychometric validation studies, focusing primarily on the practices used to determine sample size.MethodsA literature review of articles published in PubMed between January 2009 and September 2011 was conducted. Three selection criteria were applied including a search strategy, an article selection strategy, and data extraction. Agreements between authors were assessed, and practices of validation were described.ResultsData were extracted from 114 relevant articles. Within these, sample size determination was low (9.6%, 11/114), and were reported as either an arbitrary minimum sample size (n = 2), a subject to item ratio (n = 4), or the method was not explicitly stated (n = 5). Very few articles (4%, 5/114) compared a posteriori their sample size to a subject to item ratio. Content validity, construct validity, criterion validity and internal consistency were the most frequently measurement properties assessed in the validation studies.Approximately 92% of the articles reported a subject to item ratio greater than or equal to 2, whereas 25% had a ratio greater than or equal to 20. About 90% of articles had a sample size greater than or equal to 100, whereas 7% had a sample size greater than or equal to 1000.ConclusionsThe sample size determination for psychometric validation studies is rarely ever justified a priori. This emphasizes the lack of clear scientifically sound recommendations on this topic. Existing methods to determine the sample size needed to assess the various measurement properties of interest should be made more easily available.Electronic supplementary materialThe online version of this article (doi:10.1186/s12955-014-0176-2) contains supplementary material, which is available to authorized users.

Topical corticosteroid phobia is a genuine and complex phenomenon, common among French patients with atopic dermatitis, that has an important impact on treatment compliance.

Background: The objective was to solve two problems of an already validated scale measuring inpatient opinion on care: 1) a high non-response rate for some items due to the "not applicable" response option and 2) a skewed score distribution with high ceiling effect.

BackgroundThe fear of using topical corticosteroids, usually called topical corticophobia, is a frequent concern for atopic dermatitis patients and/or their parents. Assessing patients’ atopic dermatitis and their parents’ topical corticosteroid phobia is an essential step to improving adherence to treatment. Because topical corticophobia appears to be a complex phenomenon, its evaluation by binary responses (yes/no) is too simplistic. Thus, a scale is needed, which is capable of identifying the subtleties of topical corticosteroid phobia.ObjectivesTo develop and validate a scale, TOPICOP©, measuring worries and beliefs about topical corticosteroids among atopic dermatitis outpatients and their parents.MethodsAn initial statistical validation of TOPICOP was carried out, collecting qualitative data about patients’ topical corticophobia behaviors and beliefs using focus-group methodology. Then, 208 outpatients or their parents from five French centers completed a self-administered questionnaire built from focus-group results. The scale-development process comprised an explanatory principal component analysis, Cronbach’s α-coefficients and structural equation modeling.ResultsThe validated questionnaire comprised 12 items, covering two important dimensions relative to “worries” (6 items) and “beliefs” (6 items). Psychometric properties showed that items had very good communality (>0.60) within their own dimension. The final two-factor solution accounted for 47.3% of the variance. Cronbach’s α-coefficients were, respectively, 0.79 and 0.78. Structural equation modeling strongly supported the possibility of calculating a global score.ConclusionsTOPICOP© is the first scale aimed at assessing topical corticophobia in adult patients and parents of children with eczema. TOPICOP® has excellent psychometric properties and should be easy to use in everyday clinical practice for clinicians and researchers. Further studies are needed to confirm our results and validate TOPICOP© in other cultures.

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The TOPICOP score can be feasibly applied across countries and may therefore be useful for obtaining qualitative and quantitative data from international studies and for adapting patient education and treatment.

Overall, these findings provide insight into the influence of perceived supervisor support, value congruence and staffing on nurses' attitudes and behaviours.