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
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.
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,
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.
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.