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Anais Brasileiros de Dermatologia

Print version ISSN 0365-0596On-line version ISSN 1806-4841

An. Bras. Dermatol. vol.79 no.5 Rio de Janeiro Sept./Oct. 2004 



Validation of life quality questionnaires for psoriasis patients*



Gladys Aires MartinsI; Lucia ArrudaII; Aline Schaefer Buerger MugnainiIII

ISpecialist in Dermatology, M.Sc. Dermatology. Volunteer Professor at the School of Medicine, UnB. Coordinator of the Psoriasis Ambulatory, Brasília Teaching Hospital
IISpecialist in Dermatology, M.Sc. in Dermatology. professor of Dermatology - Faculty of Medicine; Head of Dermatology Service and Coordinator of Psoriasis Ambulatory at Hospital and Maternity Celso Piero - PUC/Campinas
IIISpecialist in Pediatrics





Psoriasis is a chronic disease that affects about 0.1 to 3% of the world's population and most people underestimate the social and psychological impact of the disease.1 Several studies have described the many ways in which psoriasis affects patients' lives, and techniques have been described to quantify the disability caused.1,2 It is important to assess the perceived levels of health status, disability and quality of life when considering what kind of treatment options to offer patients with psoriasis. Underscoring the importance of this, the EMC-D article focuses on a validation of two quality of life questionnaires translated into Brazilian Portuguese.

Key-words: dermatology; psoriasis; quality of life.




Psoriasis is a chronic inflammatory disease of the skin, it can cause physical and psychological discomfort, resulting in a series of adaptive restrictions. Techniques to evaluate the impact that the disease causes on the patients' daily life have been the object of various studies. The results of those publications demonstrate that psoriasis is associated to significant psychosocial comorbidity and to substantial impairment in the psoriatics quality of life.1-10

In a study carried out in the United Kingdom involving 369 patients with severe psoriasis, it was observed that the disease caused great impact on their quality of life. In that study, only 150 out of the 369 psoriatics were working, and, of those, 59% presented a relatively high degree of absenteeism due to the disease (on average 29 days working days lost per year).2

The impact of psoriasis on the quality of life of 100 patients with age varying from 20 and 70 years showed that 99% of these had already experienced overt social rejection in places such as gyms, swimming pools, hairdressers and the working environment, thus inducing feelings of discrimination.3 Patients with psoriasis have affirmed that their clinical condition triggers feelings of rage, depression, shame and anxiety, culminating in social isolation and in a greater consumption of alcohol and tobacco.4,5

According to the results of research done in the United States involving approximately 18,000 members of the National Psoriasis Foundation, the perception of those with psoriasis is that the doctors usually underestimate the impact of the disease on the patients' life, and often a condition considered severe by the psoriatic is considered less so by the doctor.6

Cutaneous diseases cause great impact on the patients' life, and approximately 10 years ago, this has began to be evaluated in a systematic way. Since then, there has been greater interest in the development of methods in dermatology to measure life quality.7

Good quality of life is perceived when "an individual's hopes and expectations are fulfilled through their experience".8 The concept of "quality of life" has been divided into several components, including the psychological, social and physical aspects.9 Quality of life in dermatology is evaluated for clinical, research and auditing reasons, as well as for political and economic objectives.

Doctors, when they decide how to manage a cutaneous disease use an intuitive method of evaluation, regarding how much the disease is affecting the patient's life, however, this can lead to a different vision from that which the patient has about his or her condition.10 More accurate measures of life quality can aid the decision making process, such as for instance, in the benefits of introducing of high cost or high risk medicines. The use of simple measures to evaluate quality of life is well received by the patients who want to express their concerns.7

Measure of the extension and severity of psoriasis11 is based on an evaluation of the signs and symptoms of the disease. However this measurement is not necessarily correlated to an evaluation of life quality. Treatment for psoriasis may halve the score for signs and symptoms, but, if the disease is located in a visible area and is still present, the life quality index may be unaffected. Consequently, this score provides an additional opinion on therapeutic effectiveness.7

The objective of this study was to validate two questionnaires translated into Portuguese (Brazilian) to evaluate the quality of life for use by dermatologists: PDI (Psoriasis Disability Index)12 and DLQI (Dermatology Life Quality Index), elaborated by Finlay.13

This study was based on the need to obtain more detailed information regarding the quality of life among Brazilian psoriasis bearers, in order that measures can be adopted to minimize the impact of the disease on the patients' life.



The author of the questionnaires for evaluation of life quality** was contacted and authorization was requested for validation of the questionnaires and also instructions on the validation procedures.

The following process was adopted: initially they were translated into Portuguese, by two independent translators. Based on those translations, a single version in Portuguese was obtained for each of the questionnaires, that was then forwarded to two other translators, for a "back-translate" (version in English). Those versions were submitted to the author for validation. This procedure took place three consecutive times until the author's final approval was obtained.

After approval of the questionnaires in the Portuguese language, the phase to evaluate reproducibility began, that involved 30 psoriasis patients accompanied at the Teaching Hospital of Brasília. Approval was obtained from the Committee of Ethics in Research of the above mentioned center. The questionnaires were answered by the patients after written consent The evaluations took place in individual sessions, to protect the patient's privacy.

They inclusion criteria were as follows:
• men and women between 18 and 65 years of age;
• men and women with psoriasis;
• capacity to understand and to agree with the terms of the study and giving free and informed consent in writing to participate.

The exclusion criteria were:
• Patients that had received a new drug under investigation in the last 30 days;
• Patients with a history of psychological disease or with conditions that could interfere in the capacity to understand the requirements of the study.

Besides the questionnaires, data were also obtained on the course of the disease, sex and marital status of each one of the patients.



In the reproducibility phase, 30 patients with psoriasis were included (18 males and 12 females) with a mean age of 39.03 years. The mean Psoriasis Area and Severity Index (Pasi) was 8.26, therefore, most (73.3%) presented moderate psoriasis; 20% presented the severe form, and only 6.7%, the mild form. The mean disease duration was 11.27 years (Table 1).



Of the total patients, 66.7% were married. Regarding the type of psoriasis, 93.3% presented the plaque form, 3.3%, psoriasis guttata, and 3.3%, the erythrodermal form.

Internal consistency of DLQI (Table 2) and PDI (Table 4): this parameter consists of analyzing the correlations (or degree of association) between the individual questions and the total score of the questionnaires. The Pearson Correlation (r) method was used, as the data presented a normal distribution (parametric). The Pearson Coefficient of Correlation (Levin, 1981): measures the correlation between two variables minimally ordinal, with a parametric or normal distribution. It varies from 0 to 1 (in module), the closer to 1, the more perfect the correlation. The degree of association can be classified as: excellent (r > 0.90), good (0.75 > r > 0.90), moderate (0.50 > r > 0.75) and weak (r < 0.50), provided it is statistically significant (p <0.05). The analysis of the coefficient of correlation in general should be used with caution, because this test measures the association between two variables, and not the causality. This fact has to be considered, because, sometimes, the items in the questionnaire might have been delineated by the author to measure aspects independent of life quality, although there could be a certain association between them.

To evaluate the capacity to discriminate subgroups with different levels of life quality, an analysis was performed to compare the mean PDI scores of the subgroups (regarding the variables of sex, marital status, educational level, severity of the psoriasis and presence of comorbidities). The statistical test used was the non-paired T Test.

Sample was divided into male and female, married and single, and associated disease (yes vs. no). There was no statistical difference in relation to the mean values of the subgroups evaluated. Results related to the severity of the psoriasis are given in table 3.

The above results refer to the T test for independent samples. When the analysis of variance was performed (Anova), no difference was detected between the groups.

It is not possible to define, however, if this pattern of results would be maintained with a larger sample without an analysis of the test power (type II error, or Beta). This analysis enables an evaluation when faced with a results without statistical difference in a sample, when, in fact, the difference could exist if larger samples or a whole population were evaluated. It should be noticed that the mild psoriasis group comprised only two individuals and the severe group of only six, against the group with a moderate degree of psoriasis, a fact that limited the comparison analysis between groups. However, that was not the main objective of this study.

Part of the Validity Construction, process included in the analysis of validation of the questionnaires, included an appreciation of the measuring properties of the two questionnaires under study, DLQI and PDI, through the Pearson coefficient of correlation.

Observation: The questions regarding symptoms and self-consciousness included in the DLQI have no equivalent in the PDI questionnaire.



In the last 10 years, the number of instruments available to evaluate the quality of the patients' life has been increasing. They can be divided in two different groups: generic and specific.14

The generic examples evaluate the life quality out of the clinical context. Of these, the best known and most used are the SIP (Sickness Impact Profile),15,16 SF-36 (the short-form 36) and NHP (Nottingham Health Profile).17,18 These questionnaires can be equally applied in the general population or used in various clinical pathologies. Their advantage consists of the fact that they can compare the life quality between diseases.14

The specific questionnaires, in turn, are used for a single disease, and since they consider the exclusive manifestations of a certain clinical condition, they are more sensitive when compared to the generic counterparts. Some of these questionnaires have been developed in dermatology, particularly for diseases such as psoriasis (PDI: Psoriasis Disability Index)12 and atopic dermatitis.14

DLQI, is a specific instrument for dermatological diseases, it was developed by Finlay and Khan,13 and comprises 10 questions. It can be used both to measure and to compare the life quality between different cutaneous diseases.14 The scores vary from 0 to 30, with the higher scores denoting a greater degree of incapacity.12

PDI, questionnaire for evaluation of life quality among patients with psoriasis, includes 15 items related to the impact of psoriasis on four areas: daily activities, work or school, leisure and personal relationships. The patient should take into account the last four weeks, and it can also evaluate the impact of psoriasis separately on each area.20

It is probable that if a larger sample was analyzed, a significant correlation between PDI and DLQI would be found in the area of work and school. The correlation between the two questionnaires in this study varied in general from weak to moderate (Table 5).



According to the answers obtained by the DLQI and PDI, the areas that had the greatest impact on the life quality of these patients were leisure and daily activities. Nichol et al have obtained an equal result. In their publication, the strongest correlation between these questionnaires was found in social function and mental health.21

It is interesting to observe that the relationship between the severity of psoriasis (Pasi) and the incapacity caused by the psoriasis was moderate. Finlay et al found a correlation between the clinical evaluation and PDI, but other authors only obtained this result when areas considered "emotionally charged", such as the face, neck and genital area, were analyzed by Pasi. These data suggest that the mild and moderate varieties of psoriasis have a strong psychosocial component.22,23,24



The degree of incapacity caused by psoriasis has been considered in the past comparable to other chronic diseases, such as diabetes and asthma, and varies substantially between patients. Some of these patients, despite presenting severe forms of the disease, prefer to live with the condition rather than undergo the adverse effects of some medicines.1 Others demand aggressive treatment event though they present mild forms of the disease. What is considered important and very incapacitating for some may be considered irrelevant by others, depending on the personal attitude and lifestyle.24

In view of this, it is very important to evaluate the perception of the sufferer of psoriasis in relation to their health condition, incapacity and life quality in order to establish the best therapeutics for each individual.

According to the validation of the translation of the questionnaires by Professor Finlay and respecting the results found in the statistical analysis, the properties evaluated in this study can be considered satisfactory (Annexes 1 and 2).



The validation of these questionnaires was made possible by support from the Roche laboratories for the statistical analysis, translations, supply of printed material and payment of the fee required by the author for use of the DLQI.



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Gladys Aires Martins
Brasília Shopping, Torre Norte, sala 930 - Asa Norte - SCN
70715-900 Brasília DF
Telefone: (61) 327-8188

Received on September 20, 2004.
Approved by the Editorial Council and accepted for publication on September 20, 2004.



* Work done at the Hospital Universitário de Brasília-DF.
** Andrew Finlay. Department of Dermatology; University of Wales College of Medicine; Wales, United Kingdom (e-mail: FinlayAY@Cardiff. ac. UK).

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