Thresholds for clinical importance were established to improve interpretation of the EORTC QLQ-C30 in clinical practice and research

Abstract

Objective: The objective of this study was to establish thresholds for clinical importance (TCIs) for the five functioning and nine symptom scales of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). Study Design and Setting: In this diagnostic study, cancer patients with mixed diagnoses and treatments completed the EORTC QLQ-C30 and anchored the questions in each domain in terms of their clinical importance. The anchor questions, concerned limitations in daily life, need for help/care, and the worries of the patient and his/her partner/family. These questions allowed categorizing patients into whether they exhibited a clinically important symptom/functional impairment for each scale and performing a receiver operating characteristic curve analysis to establish TCIs. Results: Data from 498 patients from six European countries (mean age 60.4 years, 55.2% women) were analyzed. For the TCIs generated using the patient questionnaire data, the EORTC QLQ-C30 scales showed sensitivity values between 0.71 and 0.97 and specificity values between 0.62 and 0.92 (area under the curve above 0.80 for all scales). Conclusion: This EORTC Quality of Life Group study provides TCIs for the functioning and symptom scales of the EORTC QLQ-C30. These TCIs can increase the interpretability of the questionnaire results and foster its use in daily clinical practice and in clinical research.

Thresholds for clinical importance were defined for the European Organisation for Research and Treatment of Cancer Computer Adaptive Testing Core—an adaptive measure of core quality of life domains in oncology clinical practice and research

“…Patients completed the study questionnaires (a short form based on the EORTC CAT Core and anchor items on clinical importance) either on paper or electronically via the software program Computer-Based Health Evaluation System CHES [19]. This analysis relies on the same data set that has been used previously for establishing TCIs for the EORTC QLQ-C30 [17].…”

“…In this study, we used the same anchor items as have been used previously to establish TCIs for the EORTC QLQ-C30. Details on the rationale for defining anchor items have been published elsewhere [17]. Briefly, following a mixed methods study in 150 cancer patients and health professionals [21] and a consensus meeting within the EORTC QLG, we defined clinical importance of a symptom or functional health impairment in terms of three criteria: limitations in everyday life, worries by the patient or his/her family/partner, and the need for help or care.…”

“…For RF, SF, and PA, we did not ask about limitations because interference with daily life is already included in the EORTC CAT Core for these three domains. In line with previous studies [17,22], we used the standard QLQ-C30 response format for the anchor items (a 4-point Likert scale with responses choices ''not at all,'' ''a little,'' ''quite a bit,'' and ''very much''). A patient was categorized as a case (i.e., as having a clinically important problem/symptom) if (s)he selected ''quite a bit'' or ''very much'' on any of the anchor items.…”

“…At the time of assessment, most patients (76.7%) were on-treatment (60.6% with curative intention). Further details are reported in Table 1 and elsewhere [17].…”

“…In a previous analysis [17], we established TCIs for the scales of the EORTC QLQ-C30 and found excellent diagnostic accuracy for all scales as well as invariance of thresholds across various patient groups. The EORTC CAT Core covers the same functional health and symptom domains as the EORTC QLQ-C30 but provides more flexibility regarding assessment length (number of questions) and improved measurement precision [8,18].…”