This study demonstrates that the K-SPI-Stroke questionnaire is a reliable and valid instrument. Reliability and validity are two important factors in designing a questionnaire. Reliability is concerned with the repeatability or reproducibility of the measurements while validity reflects the accuracy of the data and ensures that responses are a true reflection of the issues of interest [14–17]. To test the reliability of the K-SPI-Stroke questionnaire, we evaluated its internal consistency by using Cronbach’s α, which equals zero when the true score is not measured at all and when the data show only errors or noise; when Cronbach’s α equals 1.0, all of the items measure the true score alone without any error contributions.
The K-SPI-Stroke questionnaire had strong internal consistency, with a Cronbach’s α of 0.700 for the total signs and symptoms. However, each pattern was unsatisfactory and varied from 0.424 to 0.674. The poor reliability of the internal consistency in each pattern may suggest that the pattern constructs are not homogenous, or perhaps that the signs and symptoms are not appropriate measures of these constructs for stroke. It is likely that supplementing other patterns of K-SPI-Stroke with additional signs and symptoms, or eliminating poor signs and symptoms, may improve the reliability of the internal consistency for this questionnaire.
Cronbach’s α increased to a maximum of 0.715 when “wheezing in throat with sputum” was removed. Although this result implies that “wheezing in throat with sputum” does not measure stroke with the same validity as the other items, this item was not removed because this symptom had little influence on the overall internal consistency of the K-SPI-Stroke questionnaire.
In the analysis of the validity, we used two methods: scores comparison and a classification accuracy test. The mean score of the patients’ diagnosed pattern was significantly higher than the mean scores of the other patterns. In other words, the QDP, DPP, YDP and FHP patients reported the highest mean score for the QDP, DPP, YDP and FHP pattern, respectively. Thus, each score was a good reflection of the patient’s pathologic pattern. The second method was to compare the classification results with the physicians’ diagnoses to show the classification accuracy. The overall classification accuracy of the four patterns was 65.2 %, and the classification accuracy of the QDP, DPP, YDP and FHP was 64.13 %, 72.61 %, 41.77 %, and 68.23 %, respectively.
The YDP score was significantly higher than the scores of the other patterns (Table 2). However, the classification accuracy of the YDP (41.77 %) was lower than that of the other patterns (Table 3). This result indicates that some of the YDP items may not have accurately reflected the YDP pattern. In order words, the K-SPI-Stroke questionnaire does not discriminate YDP among the four patterns because in TKM, YDP simultaneously includes a Heat element of the FHP and a deficiency element of the QDP.