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Abstract ISPOR 

A methodological investigation to define a clinical relevant cut-off point in the ordinal scale of the EORTC QLQ-C30 questionnaire.  

All the advisory board will be included as co-authors 
 

Objectives

The objective of this analysis was to identify a clinical relevant cut-off point in the EORTC QLQ-C30 ordinal pain score by comparing patient and clinician reporting for the same symptom.  

Methods

A retrospective pooling of closed European Organisation for Research and Treatment of Cancer Randomized Controlled Trials, where the symptom pain was scored at baseline by the patient (EORTC QLQ-C30) and the clinician [Common Toxicity Criteria (CTC)], allowed secondary analysis to quantify and test the optimal cut-off point. The CTC was dichotomized as 0,1,2 vs. 3,4; defined as a clinical relevant cut-off point for clinical practice. Percent agreement with various dichotomizations of the QLQ-C30 pain scale was calculated, and McNemar’s test applied. Verification of the accuracy and generalizibility of the findings was evaluated with a validation set and by applying the same cut-off point on another symptom, i.e. fatigue.  

Results

Data at entry of study were available for pain [number of trials (t)=8, number of patients (n)=1214] and fatigue [t=5, n=1237]. Model and validation set were obtained by splitting the dataset in half. Agreement between patient and clinician dichotomized scores using different cut-off points for the QLQ-scale produced the following percentage agreement and p values for McNemar tests; median (<2.19 vs >2.19) (64%, p<.01), quartile (<=3.0 vs >3.0) (81%, p=0.55), decile (<4.0 vs 4.0) (85%, p<.01). These results indicate that the quartile split reflects best the dichotomized CTC score. This was confirmed in the validation set (quartile cut-off point: 82%, p=0.86). However, when the quartile cut-off was applied to the QLQ-C30 fatigue scale, a significant difference (p<.01) between patient and clinician results was found. 

Conclusion

Our results indicate that a quartile split of the QLQ-C30 pain score is optimal. However, a single cut-point may not generalize to other QLQ-C30 symptoms; symptom-specific cut-points may be required.