Table 4.

Construct validity of PBC-40 and PBC-27

Domains	RAND-36 scales	Pearson’s coefficient*	P value
PBC-40
Symptoms	Physical functioning	−0.535	<0.001
Symptoms	Physical pain	−0.620	<0.001
Itch	Physical functioning	−0.322	<0.001
Fatigue	Vitality	−0.834	<0.001
Cognition	Mental component summary	−0.579	<0.001
Social	Social functioning	−0.779	<0.001
Emotional	Mental health	−0.708	<0.001
Emotional	Role emotional	−0.478	<0.001
PBC-27
Symptoms	Physical functioning	−0.474	<0.001
Symptoms	Physical pain	−0.617	<0.001
Itch	Physical functioning	−0.322	<0.001
Dryness	Physical functioning	−0.423	<0.001
Dryness	Physical role	−0.262	<0.001
Fatigue	Vitality	−0.834	<0.001
Cognition	Mental component summary	−0.579	<0.001
Social	Social functioning	−0.744	<0.001
Emotional	Mental health	−0.646	<0.001
Emotional	Role emotional	−0.481	<0.001

*Pearson’s coefficients are negative because the RAND-36 scales and PBC-40/PBC-27 scales move in the opposite direction. A better HRQoL translates to a higher RAND-36 score but lower PBC-40/PBC-27 scores.

HRQoL, health-related quality of life.