Development and validation of a novel measure of adverse patient positioning in mammography

Purpose: The primary aim was to develop and validate a novel mammography positioning measure, specifically incorporating parameters which might relate to mammography pain. We then explored relationships between the new adverse positioning score and (1) pain; (2) patient and technique factors.

Methods: A 15-item instrument incorporating positioning features with potential to relate to mammography pain was developed. Participants’ mammograms (n = 310) were reviewed for presence of these features. Validity was investigated using the Rasch model. Scores produced by the resultant measure were investigated for associations with patients’ pain scores and relevant patient and technique factors, using Pearson correlation, analysis of variance, and multiple linear regression.

Results: Statistical indices within the Rasch measurement framework provided good evidence that the measure reflected a coherent construct of adverse positioning. Thus, the scores produced with the measurement instrument were valid for use in further statistical analysis. There is, however, scope for improvement of the measure’s discriminatory properties.
Adverse positioning scores were higher for greater breast volumes (r = 0.12, p=.0391) and body mass index (BMI) (r = 0.13, p=.0349), and varied by mammographer (F(11,298) 2.38, p = .0078). The relationships with BMI and mammographer persisted in regression modelling. No relationship was found between adverse positioning and pain.

Conclusions: Evidence from Rasch analysis suggests that this novel measure is valid for quantifying a coherent “adverse positioning” construct in mammography. Adverse positioning scores varied by mammographer and were related to higher patient BMI but not to mammography pain. The measure warrants expansion, further refinement, and testing in larger studies.