The Population Comparison Index: An Intuitive Measure to Calibrate the Extent of Impairments in Patient Cohorts in Relation to Healthy and Diseased Populations

Götz Gelbrich (), Caroline Morbach (), Timo Deutschbein, Martin Fassnacht, Stefan Störk and Peter U. Heuschmann
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Götz Gelbrich: Institute of Clinical Epidemiology and Biometry, University Würzburg, 97080 Würzburg, Germany
Caroline Morbach: Comprehensive Heart Failure Center, University Hospital Würzburg, 97078 Würzburg, Germany
Timo Deutschbein: Department of Medicine I, Division of Endocrinology and Diabetes, University Hospital Würzburg, 97080 Würzburg, Germany
Martin Fassnacht: Comprehensive Heart Failure Center, University Hospital Würzburg, 97078 Würzburg, Germany
Stefan Störk: Comprehensive Heart Failure Center, University Hospital Würzburg, 97078 Würzburg, Germany
Peter U. Heuschmann: Institute of Clinical Epidemiology and Biometry, University Würzburg, 97080 Würzburg, Germany

IJERPH, 2023, vol. 20, issue 3, 1-12

Abstract: We assume that a specific health constraint, e.g., a certain aspect of bodily function or quality of life that is measured by a variable X, is absent (or irrelevant) in a healthy reference population (Ref0), and it is materially present and precisely measured in a diseased reference population (Ref1). We further assume that some amount of this constraint of interest is suspected to be present in a population under study (SP). In order to quantify this issue, we propose the introduction of an intuitive measure, the population comparison index (PCI), that relates the mean value of X in population SP to the mean values of X in populations Ref0 and Ref1. This measure is defined as PCI[X] = (mean[X|SP] − mean[X|Ref0])/(mean[X|Ref1] − mean[X|Ref0]) × 100[%], where mean[X|.] is the average value of X in the respective group of individuals. For interpretation, PCI[X] ≈ 0 indicates that the values of X in the population SP are similar to those in population Ref0, and hence, the impairment measured by X is not materially present in the individuals in population SP. On the other hand, PCI[X] ≈ 100 means that the individuals in SP exhibit values of X comparable to those occurring in Ref1, i.e., the constraint of interest is equally present in populations SP and Ref1. A value of 0 < PCI[X] < 100 indicates that a certain percentage of the constraint is present in SP, and it is more than in Ref0 but less than in Ref1. A value of PCI[X] > 100 means that population SP is even more affected by the constraint than population Ref1.

Keywords: reference data; normal values; disease severity; disease score; comparability (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2023
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