Thesis (Ph.D.)--Chulalongkorn University, 2012

Readiness to change is a key factor for maintaining cardiac health behaviors including medication taking, exercise, nutrition taking, complication prevention, and symptom management throughout 3-month period after cardiac surgery. Valid and reliable instrument to measure patient’s readiness is important; however, no instrument was developed for this purpose. Aims of this study were to develop two types of scales to measure readiness to change (RTC) for cardiac health behaviors of patients following cardiac surgery. The first type was a set of 5 RTC questionnaires to measure RTC for medication taking, exercise, nutrition taking, complication prevention, and symptom management. The second type was a set of 5 readiness rulers to measure RTC of 5 behaviors mentioned above. The Transtheoretical Model was used as a theoretical basis. Content validity of both scales was assessed using a panel of experts. The original versions of both scales were pilot tested in 150 Thai cardiac surgical patients. After the revision based on pilot data findings, psychometric properties testing of the second draft scales were conducted in a sample of 533 Thai cardiac surgical patients from 4 geographic areas of Thailand. Results of the study showed that the RTC questionnaires had Cronbach’s alpha reliability ranged from .67-.86. Confirmatory factor analysis showed 4-factor structure best fit with the data. The test-retest reliability of the readiness rulers was acceptable (kappa .67-.70). However, percentage agreement of readiness stage allocation by RTC questionnaires and readiness rulers were low as 20-23%. The results revealed initial psychometric properties of the RTC questionnaires while conclusion on construct validity of readiness rulers need further study support.