Atopic dermatitis (AD) is a chronic inflammatory skin disease that causes pruritus, xerosis, and scaling. Its clinical course is marked by periods of exacerbation and remission.1,2 Little is known about the prevalence of AD in Spain. Although the International Study of Asthma and Allergies in Childhood reported that 10.3% of adolescents had had the condition at some point in their lives,3 that estimate was based on a questionnaire survey that had not been validated for use in the Spanish population The overall prevalence in adults has been estimated to be between 1% and 3%.4

AD and the pruritus it causes have a negative impact on health-related quality of life (HRQOL).5–8 Furthermore, pruritus, whether in the context of AD or not, can itself be a very debilitating symptom, leading to psychological problems and sleep disorders.9,10

The Itch Severity Scale (ISS), a recently developed and validated instrument for quantifying the intensity of pruritus and its effect, has been validated in patients with psoriasis.11 The ISS can also be used to assess the effectiveness of treatment and compare population groups.

Given the usefulness that such an instrument might have in clinical practice or research in Spain, the Spanish study group on Itch Severity in Patients With Atopic Dermatitis (PSEDA, the Spanish acronym) sought to produce a culturally adapted version of the ISS for use in both children and adults with AD. We present an analysis of the measurement properties of the Spanish version of the scale.

This naturalistic, prospective, epidemiologic, multicenter study was carried out in Spain between October 2007 and November 2008. A total of 115 dermatologists from hospitals all over the country participated.

The dermatologists selected subjects for 3 study groups: patients with AD who had clinically unstable or active lesions, patients with AD who had stable or inactive lesions, and a control group of patients who had benign skin tumors. Enrolled patients had been diagnosed at least 1 year earlier with AD (according to the criteria of Hanifin and Rajka12) or with a benign tumor. All pediatric patients were older than 2 years and younger than 18 years of age. Adults were aged 18 years or older. Patients with AD were seen at baseline and at 3 and 6 months; patients with tumors (control group) were seen only at baseline. Written informed consent was obtained from all patients (or from the parent or legal guardian of the children). The clinical research ethics committee of Hospital Universitario de La Princesa in Madrid approved the study.

The baseline visit was used to record sociodemographic variables (age, sex and education, and in adults, occupational status) and clinical variables related to AD (time since onset and severity), and concomitant diseases. Changes in AD severity were noted during both follow-up visits. Patient-centered information (self- or parent-reported) was collected at all visits by means of the ISS1 and the Dermatology Life Quality Index (DLQI),13 or the Children's Dermatology Life Quality Index (cDLQI) in the case of the pediatric AD group. The patient's own health assessment was also noted. The pediatric questionnaire was completed by the parent or legal guardian.

AD severity was assessed on the modified Eczema Area and Severity Index (mEASI),14 which gives an overall score between 0 (no disease) and 90 (maximum severity of disease).

The cDLQI and the DLQI are generic dermatologic HRQOL inventories. Each has 10 items and gives a score between 0 (minimal impact on HRQOL/good HRQOL) and 30 (maximum impact on HRQOL/poor HRQOL). The patients’ perception of their health status was assessed with a questionnaire with 7 categorical responses from “very good” to “very bad.”

The ISSa is a specific instrument for assessing and quantifying the intensity of pruritus. To develop the Spanish ISS, the original version11 was translated and culturally adapted for use in Spain following standard methods.14,15 In the definitive Spanish version finally developed (Appendix A), items are scored exactly as in the original version. The ISS contains 7 items and provides a global score between 0 (no itching) and 21 (very severe itching). Item 6, which refers to sexual desire and function is omitted from the pediatric version.

This study demonstrates that the Spanish version of the ISS is valid for use in both its adult and pediatric versions and that its measurement properties are similar to those of the original version.11 ISS scores correlated moderately with those of both the pediatric and adult versions of the DLQI.

No statistically significant differences in the sociodemographic characteristics of the AD patient and control groups were detected, indicating that the 3 groups were homogeneous. This similarity between the groups other than the finding of a greater frequency of diseases associated with AD than with benign tumors supports the robustness of the results we report.

The pediatric ISS has proven feasible for use in a Spanish population (response rate >80%) as well as valid; it is sensitive to change (large effect size) and has good internal consistency (Cronbach α more than 0.7). The properties of the pediatric version cannot be compared to those of the original ISS, which did not have a version for use in children.

The adult Spanish ISS also proved feasible and valid, with good sensitivity to change and reliability in terms of internal consistency. The correlations between ISS results on this version and scores on the mEASI and the DLQI at the baseline visit (ranging from 0.46 to 0.72) were higher than correlations found for the original version in relation to the DLQI (which ranged from 0.22-0.55).11 In both cases, however, the correlations were moderate, a finding that is not unusual in studies of the relation between clinical variables and HRQOL. A moderate correlation indicates that higher ISS scores correspond to patients with more serious AD whose state of health is poorer.

Given that itch intensity has considerable impact on a patient's health and perception of HRQOL,16 it seems reasonable for the ISS score to be related to the patient's own sense of health. In other words, the patient's report of having less itching will be consistent with feeling healthier.

The MIDs of the Spanish ISS allow us to assume that a patient will perceive improvement if there is a change of at least 4 points in the score. In the study to validate the original version of the ISS, the differences above which the instrument detected improvements was between 2.2 and 5.5 points.15

The levels of internal consistency of the Spanish version and the original version15 were also similar and in both cases over 0.7.

Test-retest reliability was found to lie between 0.61 and 0.66. Thus, this statistic did not reach or exceed the stipulated threshold of 0.70 for the Spanish version and fell below the test-retest reliability of the original. The failure to match this property is probably attributable to the difference in the timing of the first and second testing sessions in the 2 validation studies: retesting of the original version took place at 2 weeks, whereas retesting of the Spanish ISS took place after 3 months had passed. It is to be expected that test-retest reliability would be higher for the shorter period of time.

The subjective nature of itching might constitute a limitation of this study. As this symptom cannot be measured objectively, validity was assessed by comparing the Spanish ISS score to the same HRQOL questionnaire (the DLQI) that was used in validating the original version of the ISS. Other studies have found HRQOL to be affected in the presence of pruritus in patients with chronic AD,16 as well as in patients with other skin conditions, such as psoriasis17,18 or seborrheic dermatitis.19 Given these results, a dermatologist can use the Spanish ISS to monitor the degree or intensity of itching in patients as an indirect measure of the effectiveness of a treatment, to help in setting a treatment regimen for an individual patient.

This study has demonstrated that, like the original version of the ISS, the Spanish instrument has good measurement properties in terms of feasibility, validity, sensitivity to change, and internal consistency. The Spanish ISS can be useful for evaluating the intensity of pruritus in patients with AD, whether children or adults, in routine practice.

This study was funded by Astellas Pharma, SA.

Dr E. Daudén is or has been a member of advisory boards, has received consulting fees and research grants, has participated in clinical trials and received speaker's fees from the following companies: Abbott, Astellas, Biogen, Centocor Ortho Biotech Inc, Galderma, Glaxo, Janssen-Cilag, Leo Pharma, Merck-Serono, Pfizer, Novartis, Schering-Plough, Stiefel, Wyeth Pharmaceuticals, 3M, and Celgene.

Dr J. Sánchez-Pérez participates or has participated in clinical trials funded by the following pharmaceutical laboratories: Abbott, Astellas, Biogen, Galderma, Pfizer, Shering-Plough, and Wyeth Pharmaceuticals.