Validation of the Dermatology Life Quality Index as an outcome measure for urticaria-related quality of life.
BACKGROUND
Chronic idiopathic urticaria (CIU) is a debilitating skin disease that affects patients' quality of life (QOL). The Dermatology Life Quality Index (DLQI) assesses QOL parameters across several types of dermatologic conditions. However, an evaluation of the validity of the DLQI for use in CIU patients has not been undertaken, because CIU, unlike other chronic skin conditions, is subject to daily or weekly symptom fluctuations.


OBJECTIVE
To test the reliability and validity of the DLQI in 2 samples of CIU patients treated with fexofenadine hydrochloride (20, 60, 120, or 240 mg twice daily).


METHODS
Data were obtained from 2 similar multicenter, double-blind, randomized, placebo-controlled, parallel-group studies of CIU patients (n = 418 and n = 439). Patients completed the 10-item DLQI during 3 clinic visits (approximately 2 weeks apart). Clinic personnel also recorded patients' symptoms.


RESULTS
The results of the DLQI items were similar to those obtained with other skin disease populations, indicating the presence of relatively symmetrical distributions. Reliability was high, demonstrating the lack of excessive random measurement error (alpha coefficient = .89 and .87 for samples 1 and 2). Factor analysis resulted in a unidimensional pattern, supporting the use of a total DLQI score. Most DLQI items distinguished patients with varying degrees of QOL impairment, highlighting the sensitivity of this instrument. Construct validity was moderate, providing evidence that the DLQI was responsive to changes in patients' clinical status.


CONCLUSIONS
The DLQI is a valid, reliable, and clinically useful outcome measure for assessing QOL in CIU patients.
Psychometric Technologies Inc, Hillsborough, North Carolina 27278, USA. rlennox@mindspring.com
Richard D
RD
Lennox
Michael J
MJ
Leahy
D002908:Chronic Disease; D003880:Dermatology; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006634:Histamine H1 Antagonists / Q000008:administration & dosage; D006801:Humans; D017063:Outcome Assessment, Health Care; D011237:Predictive Value of Tests; D011537:Pruritus / Q000188:drug therapy / Q000523:psychology; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018434:Sickness Impact Profile; D013223:Statistics as Topic; D016593:Terfenadine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D016896:Treatment Outcome; D014581:Urticaria / Q000188:drug therapy / Q000523:psychology*
D006634:Histamine H1 Antagonists; D016593:Terfenadine; C093230:fexofenadine