Evaluating quality of life and response shift from a couple-based perspective: a study among patients with colorectal cancer and their partners.

OBJECTIVES: To examine (1) measurement invariance of quality of life (QoL) domains over time for patients with colorectal cancer and partners (i.e., response shift--recalibration, reprioritization, and reconceptualization), (2) between dyad-member measurement invariance and (3) QoL trajectories.
METHODS: Participants completed the WHOQOL-Bref preoperative (Time-0) and 3 (Time-1) and 6 months (Time-2) postoperative. A stepwise procedure, using nested factor models, examined the viability of restricting specific model parameters to be equal across measurements and between dyad members.
FINDINGS: No reconceptualization and reprioritization was detected, but indications for recalibration were present. Therefore, comparisons were restricted to group-level statistics at factor level. For patients, a decrease in the Physical Health domain occurred at Time-1 (p < 0.001), with partial recovery to baseline at Time-2 (p = 0.055). For partners, factor means in this domain remained constant (p's > 0.05) and were at each time point higher than patients' factor means (p's < 0.05). Patients' and partners' Psychological Health decreased at Time-1 (p's < 0.05), with stabilization at Time-2 (p's > 0.05). Patients and partners' factor means were comparable (p's > 0.05). Patients and partners' Social Relationship factor means decreased at Time-1 (p's < 0.05), which decreased further for patients (p = 0.011) but stabilized for partners (p = 0.214). Partners' factor means were only lower than patients' factor means at Time-1. A similar decrease in the Environmental domain factor means occurred for both patients and partners at Time-1 (p's < 0.05), with stabilization at Time-2 (p's > 0.05).
CONCLUSION: Since both patients and partners are affected by the patients' disease and treatment, we recommend that attention is paid to the couple instead of solely the patient.