Abstract
The 25-item Phlegm Pattern Questionnaire (PPQ) has been widely used to examine the relationship between the phlegm pattern (PP), quality of life, tongue colour, vocal qualities, and dysfunctional breathing. However, the concerns of response burden and differences in the respondent's abilities or item difficulty for the original version of the PPQ have not been sufficiently addressed. This study aimed to develop a short-form PPQ using Rasch analysis, an item response theory. Based on the retrospective data, the response order, differential item functioning (DIF), dimensionality, reliability, concurrent validity, and fitting errors were examined for 291 normal participants and 61 inpatients. The discriminative ability of the short-form PPQ was examined using receiver operating characteristic curve analysis. Along with Rasch analysis, another short-form PPQ was developed using equidiscriminative item-total correlation (EITC) analysis and the results between the two short-form PPQs were compared accordingly. Rasch analysis results suggested a 6-point response category for the PPQ, and finally, 8 items without fitting errors or DIF variability were selected for the PPQ (PPQ-8). The PPQ-8 had satisfactory reliability (person separation index = 2.23), unidimensionality (unexplained variance in the first contrast = 1.598), fitting levels (infit mean square, 0.80–1.39; outfit mean square, 0.79–1.34), sensitivity (70.5%), and specificity (76.5%). The PPQ-8 had a moderate discriminative ability of the PP (area under the curve = 0.759), and the cut-off point was 23. Although the 8-item PPQ developed using EITC analysis showed similar levels of reliability, validity, and discriminative ability of the PP to the PPQ-8, it could not present the information of item hierarchy and differences in the respondents' abilities. In conclusion, the PPQ-8 by Rasch analysis is recommended for future use to evaluate the clinical severity of PP.
Highlights
According to the traditional Chinese medicine theory, a pathological pattern is a subcategory of a disease or disorder referring to a diagnostic conclusion based on the pathological changes at a certain stage of disease [1]
Like most questionnaires developed by classical test theory, the original Phlegm Pattern Questionnaire (PPQ) version was limited in that it could not present the information of item hierarchy relating to the respondents’ ability and item difficulty. erefore, Rasch analysis was utilised to address concerns regarding the difficulty of items and the ability of the subjects to answer the PPQ
It should be noted that despite satisfactory reliability and discriminative ability, a limitation of the 8item PPQ by equidiscriminative item-total correlation (EITC), that it did not present the information of item hierarchy or differential item functioning (DIF) characteristics for the subgroups, might remain. Another concern of the 8-item PPQ by EITC was that the determination of the item numbers of the PPQ was somewhat arbitrary because the item numbers in the EITC analysis were forced to match those in the Rasch analysis. erefore, this study suggested that PPQ-8 by Rasch analysis might be preferable to EITC for future use to evaluate phlegm pattern (PP)
Summary
According to the traditional Chinese medicine theory, a pathological pattern is a subcategory of a disease or disorder referring to a diagnostic conclusion based on the pathological changes at a certain stage of disease [1]. Among the diverse pathological patterns, phlegm is a viscous, turbid pathological product that accumulates in the body and covers the areas where fluid or lymphatic circulation may be retarded [5]. Similar to traditional Chinese medicine, Korean medicine recognises that the accumulation of phlegm leads to nasal discharge or sputum and diverse neurological and gastrointestinal problems, including dizziness, palpitation, ingestion, and mucousy stool [6]. Traditional Persian medicine has recognised that the balance among the “4 humours” (black bile, yellow bile, phlegm, and blood) in the human body sustains health preservation, while the lack of this balance results in diseases, especially the dystemperament state [7]. Due to the wide spectrum of pathophysiology and high affinity towards other pathogenic factors, a Korean medical doctor must identify the presence
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