Reliability and validity of a new scale on internal coherence (ICS) of cancer patients

Abstract Background Current inventories on quality of life used in oncology mainly focus on functional aspects of patients in the context of disease adaption and treatments (side) effects (EORTC QLQ C30) or generically the status of common functions (Medical Outcome Study SF 36). Beyond circumscribed dimensions of quality of life (i.e., physical, emotional, social, cognitive etc.), there is a lack of inventories which also address other relevant dimensions such as the 'sense of coherence' (SOC) in cancer patients. SOC is important because of its potential prognostic relevance in cancer patients, but the current SOC scale has mainly been validated for psychiatric and psychosomatic patients. Our two-step validation study addresses the internal coherence (ICS) scale, which is based on expert rating, using specific items for oncological patients, with respect to its reliability, validity and sensitivity to chemotherapy. Methods The items were tested on 114 participants (57 cancer patients and a matched control group), alongside questions on autonomic regulation (aR), the Hospital Anxiety and Depression Scale (HADS), self-regulation (SRQ) and Karnofsky the Performance-Index (KPI). A retest of 65 participants was carried out after a median time span of four weeks. In the second part of the study, the ICS was used to assess internal coherence during chemotherapy in 25 patients with colorectal carcinoma (CRC) and 17 breast cancer patients. ICS was recorded before, during and 4 – 8 weeks after treatment. Results The 10-item scale of 'internal coherence' (ICS) shows good to very good reliability: Cronbach-α r = 0.91, retest-reliability r = 0.80. The ICS correlates with r = 0.43 – 0.72 to the convergence criteria (all p < 0.001). We are able to show decreased ICS-values after the third cycle for CRC and breast cancer patients, with a subsequent increase of ICS scores after the end of chemotherapy. Conclusion The ICS has good to very good reliability, validity and sensitivity to chemotherapy.