Journal Information
Vol. 109. Issue 4.
Pages 365-366 (May 2018)
Vol. 109. Issue 4.
Pages 365-366 (May 2018)
Case and Research Letter
DOI: 10.1016/j.adengl.2017.02.029
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Source of Bias in the Spanish Language Version of the WPAI:PSO (Work Productivity and Activity Impairment—Psoriasis v.2.0) Questionnaire
Sesgo en el Cuestionario de productividad laboral y deterioro de las actividades: psoriasis (WPAI:PSO v2.0) en la población española
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E. Margarita,b,
Corresponding author
emargarit@santpau.cat

Corresponding author.
, A. López-Ferrera, E. Vilarrasaa, L. Puiga
a Servicio de Dermatología, Hospital de la Santa Creu i Sant Pau, Universidad Autónoma de Barcelona (UAB), Barcelona, Spain
b Facultad de Psicología, Universidad Autónoma de Barcelona (UAB), Bellaterra, Barcelona, Spain
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Tables (2)
Table 1. Categorized Responses to Our Survey Question About Work Status.
Table 2. Contingency Table Showing Reported Work Status Distributed According to Responses to Item 1 of the Spanish WPAI:PSO v.2.0 Versus Our Survey Records.
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Dear Editor:

The 6-item Work Productivity and Activity Impairment–Psoriasis questionnaire (the WPAI:PSO)1 has been used in numerous clinical trials and other studies to evaluate the impact of psoriasis. It is supported by the WPAI validation study,2 version 2.0 of the Spanish language adaptation (the WPAI:PSO v.2.0),3 and a validated adaptation to Spanish of the general health version of the questionnaire (the WPAI:GH).4 This questionnaire, which measures effects on both work and other activities of daily living, includes items to be answered with yes or no, a time estimate in hours, or a choice on a 10-point scale. In our clinical practice in Spain we have detected that patients with psoriasis who are not employed by a company under a so-called indefinite contract—one that does not have a term limit—often do not respond as expected to the question on work status in the WPAI:PSO v.2.0.

We devised an observational, cross-sectional survey to assess the validity of information obtained from the Spanish questionnaire's first item, on work status: “¿Está actualmente empleado (tiene un trabajo a sueldo)?” Back-translated to English, this item would be “Are you currently employed? (Do you have a job with a salary?).” We enrolled 50 patients diagnosed with psoriasis in the dermatology department of Hospital de la Santa Creu i Sant Pau in March and April 2016. Participants had to be over the age of 18 years and give their written informed consent to inclusion before undergoing any part of the study. They then responded to the Spanish WPAI:PSO v.2.0 in a room in our outpatient clinic. After they had completed the questionnaire, we recorded age, sex, and work status. To give us this last information, the patients answered the Spanish question, “¿Realiza actualmente algún tipo de trabajo remunerado?” (“Are you currently doing some type of paid work?”) The respondent was then asked to give specifics about the work situation. Their answers are categorized in Table 1.

Table 1.

Categorized Responses to Our Survey Question About Work Status.

Work Situation  No. of Patients 
Employee (with an indefinite-term contract)  24  48 
Unemployed  14 
Retired 
Homemaker 
Student 
On sick leave 
Othera  10  20 
a

Situations including freelance work, jobs done off the books (compensated with cash in hand that is not reported for tax purposes), internships or work done under a grant, or ownership of a business.

All of the recruited patients agreed to participate. The mean (SD) age was 44.46 (13.69) years, and 60% were men. We detected no significant differences in responses according to sex or age. The correlation between our survey findings and the information from item 1 of the questionnaire was high (α=0.81). All patients with employee status and who received a salary answered the WPAI:PSO question correctly. However, a comparison with the work situations recorded in our survey (Table 1) revealed that 9 of the 10 working patients in the category “other” (18% of the total) responded incorrectly to item 1 of the Spanish WPAI:PSO v.2.0 (Table 2).

Table 2.

Contingency Table Showing Reported Work Status Distributed According to Responses to Item 1 of the Spanish WPAI:PSO v.2.0 Versus Our Survey Records.

  No, Not Working (Our Survey)  Yes, Working (Our Survey) 
No, not working (WPAI:PSO v.2.0)  16 (32%)a  9 (18%)b 
Yes, working (WPAI:PSO v.2.0)  0 (0%)  25 (50%)c 

ABBREVIATION: WPAI:PSO v.2.0, Work Productivity and Activity Impairment—Psoriasis, version 2.0 in Spanish.

a

Patients who were officially unemployed, retired, homemakers, students, or on sick leave.

b

All 9 were in the category “Other” (Table 1), which includes freelancers, those working off the books or receiving stipends from a grant, or business owners.

c

Salaried workers plus others.

The incorrectly responding patients were all freelancers, occasional-contract workers, or persons working without any contract whether legally or not. These 9 patients answered no to the Spanish item 1, which asked specifically if they had a “job with a salary.” We should point out that Spain had 1974881 persons registered as doing freelance work on September 30, 2016, namely 10% to 11% of the country's active population.5 In addition, a small portion of workers have no contract and are paid sums that are not legally declared. Statistics about such workers are not available, but most patients in this situation who come to our clinic will report that they do not work at all because they fear revealing that they work illegally.

Given the results of our study, we then examined the original English version of item 1 of the questionnaire, which asks, “Are you currently employed (working for pay)?” The definition of the word pay includes any type of monetary compensation. The Spanish version, on the other hand, specifies compensation received as a salary, which is a fixed regular payment made to a worker or professional within a company. This subtle difference presents us with a possible problem in the Spanish adaptation of the English questionnaire.

A new, validated adaptation to Spanish of the WPAI for use in Crohn disease (the WPAI:CD, v.2.1)6,7 has rendered item 1 as follows: “¿Está actualmente empleado (tiene un trabajo remunerado)?” The back-translation of the parenthetical phrase would be, “Do you do paid work?” The use of paid work rather than salary widens the meaning of the concept of work considerably, so that respondents can more clearly see what information the questionnaire is attempting to elicit. In spite of the availability of this version for Crohn disease, most studies of Spanish patients with psoriasis use the WPAI:PSO v.2.0.

In summary, in order to obtain more reliable responses to the Spanish WPAI:PSO v.2.0, clinicians should explain item 1 to patients, saying it asks them to report any type of paid work, not just work done in a salaried position. Patients should also be reminded that the questionnaire they are filling out is not concerned with the legality of their work situation and that the information they provide will remain completely anonymous. It would be useful to make a new version 2.1 of the Spanish WPAI:PSO available in order to avoid bias in gathering information from our patients with psoriasis.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

References
[1]
WPAI:PSO 2016 [cited 2016 Feb 19]. Available from: http:www.reillyassociates.net/WPAI
[2]
M.C. Reilly, A.S. Zbrozek, E.M. Dukes.
The validity and reproducibility of a work productivity and activity impairment instrument.
Pharmaco Economics, 4 (1993), pp. 353-365
[3]
WPAI:PSO (v2.0 Spanish-Spain) 2016 [cited 2016 Feb 19]. Available from: http://www.reillyassociates.net/WPAI_Translations.html
[4]
M.C. Gawlicki, M.C. Reilly, A. Popielnicki, K. Reilly.
Linguistic validation of the US Spanish work productivity and activity impairment questionnaire, general health version.
Value Health, 9 (2006), pp. 199-204
[6]
M. Vergara, A. Montserrat, F. Casellas, M. Maudsley, O. Gallardo, E. Ricart, et al.
Validation of the Spanish Work Productivity and activity impairment questionnaire: Crohn's disease version.
Eur J Gastroenterol Hepatol, 21 (2009), pp. 809-815
[7]
M. Vergara, A. Montserrat, F. Casellas, A. Villoria, D. Suarez, M. Maudsley, et al.
A new validation of the Spanish Work Productivity and Activity Impairment questionnaire Crohn's disease version.
Value Health, 14 (2011), pp. 8849-8861

Please cite this article as: Margarit E, López-Ferrer A, Vilarrasa E, Puig L. Sesgo en el cuestionario de productividad laboral y deterioro de las actividades: psoriasis (WPAI:PSO v2.0) en la población española. Actas Dermosifiliogr. 2018;109:365–366.

Copyright © 2017. Elsevier España, S.L.U. and AEDV
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