Rasch-assisted medical diagnosis

The Rasch model has the great advantage for clinical practice that it allows the practitioner to examine and diagnose subject behavior patterns. Post-Traumatic Subjective Syndrome (PTSS) is a condition following from skull trauma, and can be identified through 14 symptoms. Though these symptoms are not recognized in normal medical instrumental examinations, they may nevertheless cause patients to feel unwell.

Our study consisted of 26 subjects. Following skull trauma and consequent coma (averaging 1.9 minutes), they experienced symptoms which - organic causes having been excluded - were considered due to PTSS. All patients were asked whether they had experienced one or more of the 14 PTSS symptoms. Initial Rasch analysis revealed a poor fit for one symptom "dysmnesia", so this was dropped from subsequent analysis.

The Table (in the printed text) shows the remaining 13 symptoms and the 12 possible non-extreme scores. Rasch analysis produced subject measures and item calibrations on an "intensity of PTSS symptoms" variable. Each cell contains the probability of reporting a symptom given the symptom's calibration and the measure corresponding to a subject's raw score. This table is a useful tool for clinical diagnosis of PTSS. When a patient suffering from 5 of the 13 symptoms (r=5, Br=-.6) includes "insomnia", this symptom is usual, because its probability of occurrence is high (p=.6). But the same cannot be said when a patient reports the occurrence of "phobias", because these are infrequent (p=.2) at a score of 5.

"What is the probability of clinical PTSS?" First, the fewer the symptoms, the less likely is PTSS, but now, which symptoms are reported for a given raw score is also important. The less expected a reported symptom for a score, the less likely the medical diagnosis is PTSS. Thus combining expert knowledge with Rasch statistics enables us to construct a prediction equation for clinical diagnosis of PTSS from patient measures and fit statistics.

Medical diagnosis. Cristante F, Robusto E. … Rasch Measurement Transactions, 1995, 8:4 p.395

Rasch Books and Publications
Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, 2nd Edn. George Engelhard, Jr. & Jue Wang	Applying the Rasch Model (Winsteps, Facets) 4th Ed., Bond, Yan, Heene	Advances in Rasch Analyses in the Human Sciences (Winsteps, Facets) 1st Ed., Boone, Staver	Advances in Applications of Rasch Measurement in Science Education, X. Liu & W. J. Boone	Rasch Analysis in the Human Sciences (Winsteps) Boone, Staver, Yale
Introduction to Many-Facet Rasch Measurement (Facets), Thomas Eckes	Statistical Analyses for Language Testers (Facets), Rita Green	Invariant Measurement with Raters and Rating Scales: Rasch Models for Rater-Mediated Assessments (Facets), George Engelhard, Jr. & Stefanie Wind	Aplicação do Modelo de Rasch (Português), de Bond, Trevor G., Fox, Christine M	Appliquer le modèle de Rasch: Défis et pistes de solution (Winsteps) E. Dionne, S. Béland
Exploring Rating Scale Functioning for Survey Research (R, Facets), Stefanie Wind	Rasch Measurement: Applications, Khine	Winsteps Tutorials - free Facets Tutorials - free	Many-Facet Rasch Measurement (Facets) - free, J.M. Linacre	Fairness, Justice and Language Assessment (Winsteps, Facets), McNamara, Knoch, Fan
Other Rasch-Related Resources: Rasch Measurement YouTube Channel
Rasch Measurement Transactions & Rasch Measurement research papers - free	An Introduction to the Rasch Model with Examples in R (eRm, etc.), Debelak, Strobl, Zeigenfuse	Rasch Measurement Theory Analysis in R, Wind, Hua	Applying the Rasch Model in Social Sciences Using R, Lamprianou	El modelo métrico de Rasch: Fundamentación, implementación e interpretación de la medida en ciencias sociales (Spanish Edition), Manuel González-Montesinos M.
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar	Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch	Rasch Models for Measurement, David Andrich	Constructing Measures, Mark Wilson	Best Test Design - free, Wright & Stone Rating Scale Analysis - free, Wright & Masters
Virtual Standard Setting: Setting Cut Scores, Charalambos Kollias	Diseño de Mejores Pruebas - free, Spanish Best Test Design	A Course in Rasch Measurement Theory, Andrich, Marais	Rasch Models in Health, Christensen, Kreiner, Mesba	Multivariate and Mixture Distribution Rasch Models, von Davier, Carstensen

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