Measuring counted fractions in healthcare
Measuring counted fractions in healthcare
Índice
1. Counted fractions in healthcare
2.Quality assurance of counted fractions
3. Restitution of counted fractions and metrological references
4. Case studies
5 . Metrological item banks
In establishing metrological quality assurance in healthcare, one major hurdle is the correct treatment of ordinal data typical of questionnaires, performance tests and other categorical data collected widely in care.
Despite being known well over a century, there are still many examples of measurements in healthcare – for example, (i) on-line tables of percentage performance indicators (e.g. fraction of patients seeing a doctor within seven days) and (ii) correlation plots for Alzheimer sufferers of cognitive scores against biomarker concentration – where the ‘counted fraction’ distortion of scales is not compensated for. The Rasch form of generalised linear model not only handles counted fraction ordinality but also enables separation of object and instrument attributes (such as task difficulty and patient ability) essential for metrological restitution in measurement systems in healthcare. A perspective is given of a new kind of certified reference material employing causal Rasch models in terms of construct specification equations for metrological item banking in the social sciences. This is part of the response to a recent call for: ‘a new international body to bring together metrology, psychometrics, philosophy, and clinical management to support the global comparability and equivalence of measurement results in patient centred outcome measurement to improve healthcare’.
Prof. L R Pendrill, Ph D Atomic Physics 1978, has until recently been R&D Director at Measurement Technology Division and the National Metrology Institute of SP at Borås. He plays a leading role, nationally and internationally, recently as Chairman (2009-12) for EURAMET (www.euramet.org), the European association of national metrology institutes in Europe. Pendrill is currently Chair of ISO/TC12 Quantities & Units. He develops new quality-assured measurement methods in which Man is focus by measuring PCOM (e.g. perceived comfort), as well as optimised measurement uncertainty, where the effects of measurement are weighed against the effects of product evaluations.
Dr. J Melin has the last years been working with measurements in health care. She is now working at the division for Metrology at RISE Research Institute of Sweden, where she is included in several project where person-centered metrology is used and further developed. During her PhD project she took part in the development of the PPRQ at the Gothenburg Centre for Person-Centred Care (GPCC). After her dissertation in December 2016 she has both continue the development of PPRQ and her skills in metrology.
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Metrology; Quality assurance; Rasch Measurement Theory; Psychometrics
