Applying the Generalizability Theory to Identify the Sources of Validity Evidence for the Quality of Communication Questionnaire.

Effective doctor-patient-family communication is an integral and sensitive part of health care, assessing its quality is essential to identify aspects needing disclosure and, if necessary, improvement. Cross-sectional study aimed to analyze the sources of evidence of validity and the number of participants needed to reliably apply the Quality of Communication Questionnaire (QoC) through Generalizability Theory (GT). The mean age of the 150 patients hospitalized at the end of life was 50.5 (SD = 13.8) years, the mean hospital length of stay was 7.5 (SD = 10.2) days, 56.9% were male. Regarding the 105 patients' family members of patients whose mean length of hospital stay was 9.5 (SD = 9.1) days, their mean age was 42.2 (SD = 14.7) years, 69.5% were female. GT was used to quantify the minimum number of questionnaires needed, with the aim of reaching a reliable estimate of QoC with G-coefficients. To reach a reliability of .90, there is a need for 25 for the Eρ² questionnaires and 35 for the Φ. The exact estimation identified the minimum number of questionnaires required for the evaluation of physicians by patients. To obtain a reliability of .90, there is a need for 30 and 40 questionnaires for the G-coefficients. A practical and fast application makes it possible to use QoC in its entirety or alone to evaluate general communication or communication about palliative care. Furthermore, based on these results, it was possible to identify which aspects were effective or ineffective in these contexts.