Reliability and Validity of the Greek QLQ-C30 and QLQ-MY20 for Measuring Quality of Life in Patients with Multiple Myeloma

Table 2

Summary results of scaling assumption tests.

	𝑁^a	Item-internal consistency		Item-discriminant validity
		Range of correlations^b	# Success/total^c	Range of correlations^d	# Success/total^e
QLQ-C30
Global health status/QoL	2	0.85	2/2	0.34–0.59	16/16
Functional scales
Physical functioning	5	0.35–0.73	4/5	0.17–0.55	27/40
Role functioning	2	0.82	2/2	0.27–0.64	15/16
Emotional functioning	4	0.62–0.74	4/4	0.21–0.68	29/32
Cognitive functioning	2	0.40	2/2	0.10–0.47	2/16
Social functioning	2	0.65	2/2	0.22–0.51	10/16
Symptom scales/items
Fatigue	3	0.75–0.83	3/3	0.27–0.57	22/24
Nausea and vomiting	2	0.66	2/2	0.08–0.41	16/16
Pain	2	0.67	2/2	0.14–0.56	12/16
QLQ-MY20
Disease symptoms	6	0.18–0.68	5/6	0.01–0.51	9/12
Side effects of treatment	9^f	0.23–0.57	5/9	0.03–0.43	6/18
Future perspective	3	0.60–0.69	3/3	0.16–0.38	6/6

^aNumber of items and number of item-internal consistency tests per scale (single-item scales excluded).
^bRange of correlations between items and hypothesized scale corrected for overlap.
^cNumber of correlations exceeding the 0.40 standard/total number of correlations.
^dRange of correlations between items and other scales.
^eNumber of successful discriminant validity tests/total number of discriminant validity tests.
^fItem no.42 concerned only 10% of the sample suffering hair loss and was omitted from this analysis.