| ObjectiveFirstly, to develop the "Main Symptom scale for Psoriasis Vulgaris" using main symptom as item and to assess its reliability and validity in order to provide an effective measuring tool for evaluation of Chinese medicine. Secondly, preliminary assessment of the Minimal Clinically Important Deferences of Dermatology Life Quality Index, DLQI used in the clinical trial "A Single-blind, Randomized and Controlled Clinical Trial of Auricular Therapy with topical Western medicine in treatment for Psoriasis Vulgaris " (registration number:ChiCTR-TRC-14004916) as an outcome measure.MethodsThis study follow the steps of the FDA guidance of developing a PRO instrument by organizing a working group, ancient and modern literature review to analyze the main symptoms of psoriasis vulgaris, hypothesizing conceptual framework, selecting or generating main symptom items by Delphi, selecting recall period and response, interpreting main symptom to questions easily understood by patients and finally draft the "Main Symptom scale for Psoriasis Vulgaris ".212 patients of psoriasis vulgaris were enrolled to the cross-sectional survey using the new instrument. Clinical data were analyzed through psychometric techniques to assess the acceptability, reliability, and validity of the scale. There were 99 valid data from the clinical trial that we could use to evaluate the MCID of DLQI using distribution-based method and anchor-based method respectively.ResultsThe preliminary version of the "main symptoms of psoriasis Scale" include a total of 14 main symptom items, of which the 14th item only applied to females.213 scales were handed out while 212 returned(99.5%), and 209 finished(98.6%).The data of 209 psoriasis patients,145 males and 58 females with 6 patients unclear due to no sex on the scales was analyzed by SPSS17.0. The average test-retest Spearman’s correlation coefficient was 0.877(P＜0.01).The internal consistency reliability was high (Cronbach’s alpha for the scales of 13 item,0.864 14 item 0.872). The Spearman-Brownwere of Split-half reliability coefficients were 0.825 (13 item) and 0.858 (14 item); Evidence of factor structure validity of scale was demonstrated by both exploratory factor analysis that accounted for 51.27896(13 item, extracted in two common factors, KMO= 0.865,χ2= 914.260, P<0.001) and 71.78%(14 item, extracted in four common factors, KMO= 0.752,χ2= 334.056, P<0.001)) of the total variance. Related validity between PASI severity(mild:PAIS <7.moderate:7≤PASI≤12.severe:PASI>12) and the scale(13 item) showed mild to moderate positive correlation with Spearman correlation coefficients of 0.261 (P<0.05). Correlations between the scale and SAS or SDS were also showed positive correlation(SAS:r= 0.551 (13 item), P＜0.001; r=0.756 (14 item),P<0.001; SDS:r= 0.389 (13 item), P＜0.001; r= 0.736 (14 item), P <0.001).In the trial of "A Single-blind, Randomized and Controlled Clinical Trial of Auricular Therapy with topical Western medicine in treatment for Psoriasis Vulgaris",99 patients’data went into analysis. The internal consistency reliability of DLQI is high(range of Cronbach’s alpha for baseline 0.873, for 4 week 0.875). The Spearman-Brownwere of Split-half reliability coefficients were 0.815(0 week) and 0.875(4 week) rFour weeks after intervention, DLQI score improved in both groups(rate of change was 26.14%, and rank test Z--5.354, P< 0.001),standardized effect size, ES and standardized response mean, SRM were 0.464,0.577 respectively. The MCID of DLQI was 2.53 using reduction of PASI as anchor (PASI decrease<25%, PASI decrease between 25%-49%, PASI decrease between 50-74%, PASI decrease≥75%), which meant, when DLQI decreased 2.53 after treatment, PASI decreased at least above 50%;Effect size ES, Standard Deviation SD and standard error of measurement SEM, were assessed using the distribution-based method respectively. The MCID value obtained for 0.5ES,0.5SD,1SEM were 0.23,2.58,1.84 respectively. Therefore, the MCID value of DLQI in this study was range from 1.84 to 2.58.Conclusion1. It was feasible and scientific to develop the new PRO instrument "Main Symptom scale for Psoriasis Vulgaris". It could provide references for other diseases to develop such a similar instrument using main symptom as item..2. "Main Symptom scale for Psoriasis Vulgaris" had evidence of good" reliability and validity and it might be an effective measurement tool in the treatment evaluation for psoriasis vulgaris with Chinese medicine.3. Combination of distribution-based method and anchor-based method were used frequently and effectively to assess MCID.4. There was different MCID values after assessing by two different methods. Further research should increase sample size. |
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