The relationship between plasma beta-endorphin and the dimensions of the Chinese Cancer Pain Assessment Tool (CCPAT)

Purpose. The purpose of the study was to identify the relationship between plasma β-endorphin (objective variable) and the dimensions of the Chinese Cancer Pain Assessment Tool (CCPAT) (subjective variables). The dimensions included functional, pharmacological, psychosocial, pain beliefs and meanings, emotional and pain intensity. Methods. In this correlational study, 48 Chinese patients who had experienced cancer pain in the 24 hours before the investigation were recruited from an oncology unit by convenience. CCPAT scores and venous blood for β-endorphin were taken from each subject concurrently on two occasions, 8 a.m. and 8 p.m. Plasma β-endorphin was measured by radioimmunoassay. Results. Thirty-eight men and nine women were recruited. With the exception of 14 subjects who did not have the blood-taking procedure in the evening, all subjects completed the CCPAT and their blood was taken. Nineteen subjects suffered from gastrointestinal cancers, 17 from nasopharyngeal carcinoma, 9 from lung cancer and 2 from other types. Twenty-four of them did not have known metastasis. The mean age was 48.8 (SD 11.5). The mean β-endorphin levels for 8 a.m. and 8 p.m. were 42.55 pg/ml (SEM = 5.47) and 42.15 pg/ml (SEM = 5.80) respectively. There was no significant difference between the morning and the evening β-endorphin levels. The mean weighted scores for the functional, psychosocial, pharmacological, emotional, pain belief and meaning and intensity dimensions were 40.02, 13.85, 21.72, 25.37, 25.77, 62.17 and 2.35, respectively. A stepwise regression was done to examine the relationships among the β-endorphin levels and the scores of the six dimensions. The regression model was significant (p = 0.02). A cluster analysis was performed and the results supported the contention that a link may exit between the six dimensions and plasma β-endorphin levels. Conclusions. The importance of psychosocial, emotional and intensity factors in assessment of pain is re-affirmed by this study using β-endorphin as a biological benchmarker.