Self-Estimated Functional Inability because of Pain questionnaire for Brazilian workers with musculoskeletal pain: face and content validity

ABSTRACT Our study aimed to perform the face and content validity of Self-Estimated Functional Inability because of Pain (SEFIP) for workers, here called the SEFIP-work questionnaire. This is a questionnaire validity study. Our group previously translated and adapted the original version of the SEFIP, which was developed to investigate musculoskeletal pain and dysfunction to be applied to dancers (SEFIP-dance). However, due to the broad scope of the SEFIP-dance, we made changes and adaptations in the Brazilian Portuguese version of the SEFIP-dance to allow its use in workers. Therefore, face and content validity were performed for the development of the SEFIP-work based on opinions of committee of occupational disease and rehabilitation experts. After face and content validity, this SEFIP-work version was applied to 30 working individuals with musculoskeletal pain. The participants were native Brazilian Portuguese speakers aged 18 years and older. Thus, three changes were made to the questionnaire. All participants understood the SEFIP-work items and alternatives. The average total SEFIP-work score was 6.59 (SD=3.66), with the item “parte inferior das costas” (lower back) being the most marked (n=28; 93.33%), with an average score of 1.18 (SD=0.73). In conclusion, the Brazilian Portuguese version of SEFIP-work presents an acceptable level of understanding by workers in the investigation of musculoskeletal pain or discomfort.


INTRODUCTION
Researchers and occupational health professionals have used different occupational health assessment instruments to implement preventive, ergonomic, and/or rehabilitation measures [1][2][3][4] . Most of these instruments are questionnaires and, due to their basic characteristics, are based on the measurement of variables related to the worker's own report, as in the case of pain investigation 5,6 .
In general, we can divide occupational health evaluation into ergonomic assessment and worker's health assessment. Within the context of ergonomics and its relationship to biomechanical risks during the execution of work tasks, the instruments commonly used for this evaluation are: Rapid Upper Limb Assessment 1 , Rapid Entire Body Assessment 4 , Quick Exposure Check 3 , and Rapid Office Strain Assessment 2 .
Regarding occupational health, several variables can be measured by questionnaires. The Need for Recovery Scale is a questionnaire that measures worker's fatigue 7 ; the Strain Index measures risk of upper limb dysfunction 1 ; the Maastricht Upper Extremity Questionnaire investigates arm, cervical, and shoulder involvement 8. In addition to these specific instruments, there are questionnaires to measure various dimensions of pain, including the Numerical Rating Scale 5 and Örebro Musculoskeletal Pain Questionnaire 6 .
Despite the wide variety of questionnaires for workers' health, the Nordic Musculoskeletal Questionnaire (NMQ) is still the most used instrument. This instrument was developed approximately three decades ago and allows for regionalized measurement of musculoskeletal pain, i.e., considering separate body parts. Musculoskeletal pain in the NMQ is investigated at two different times: the previous 12 months and last 7 days 9,10 . However, the NMQ lacks a severity or disability score.
In addition to and based on the NMQ, researchers developed a questionnaire to assess musculoskeletal pain in dancers entitled the Self-Estimated Functional Inability because of Pain (SEFIP-dance). The SEFIPdance also contains a disability score that ranges from 0 to 4 points, a feature that allows for a total score 11 . Given this context and considering the broad and generic construction of this questionnaire, our study aimed to perform the face and content validity of SEFIP for workers, here called the SEFIP-work questionnaire. Our hypothesis is that the adapted SEFIP-work questionnaire is adequately understood by the target population of our study.

Study design
This questionnaire validity study was conducted based on the Guidelines for the Process of Cross-cultural Adaptation of Self-Report Measures 12 and Consensus-based Standards for the Selection of Health Measurement Instruments 13 .
Our study was conducted at the Department of Physical Education of the Universidade Federal do Maranhão (São Luís, MA, Brazil). All participants included in the study signed an informed consent form. The study participants were recruited from communities around the university by verbal invitations, posters, and social media.

Adaptation of the SEFIP-work questionnaire
Our group previously translated and adapted the original version of the SEFIP, which was developed to investigate musculoskeletal pain and dysfunction in dancers (SEFIP-dance) 14 . However, due to the SEFIPdance broad scope, we made changes and adaptations in the Brazilian Portuguese version to allow its use in workers (SEFIP-work). Therefore, face and content were validated in two stages for the development of the SEFIP-work 15 . A committee of occupational disease and rehabilitation experts was consulted to adjust or change the SEFIP-dance. This consultation provided features for the SEFIP-work to enable its application to workers.
In the first stage, four physical therapists that work in occupational disease rehabilitation were instructed to perform technical judgment, alterations, inclusion, or exclusion of items. Moreover, these four physical therapists were asked to give their opinion on the ability of the SEFIPwork to measure musculoskeletal-pain-related disability.
In the second stage, four healthcare professionals were consulted to verify possible difficulties in reading the questionnaire, clarity of response alternatives, presence of typographical errors, font size, level of understanding of items, length, application time, and overall evaluation.
We have adopted the following inclusion criteria for physical therapists: working with occupational health for at least 24 months; be native and fluent in Brazilian Portuguese; be available for meetings and consultations to clarify the opinion issued. For healthcare professionals (two physical therapists and two physical education professionals), we adopted the following inclusion criteria: prior experience using questionnaires in patient assessment; be Brazilian and speak Brazilian Portuguese as mother tongue; be available for meetings and consultations to clarify the opinion issued.
After face and content validation, with 100% of agreement of the experts, the pre-final SEFIP-work version was established and applied to 30 workers with musculoskeletal pain. The participants were aged 18 years and older with Brazilian Portuguese as their mother tongue. Participants answered the questionnaire and established their understanding of the pre-final version of the SEFIPwork by ticking "yes" or "no" for each item. An item understood by less than 20% of the participants would be changed and retested in a new sample of 30 participants until the achievement of the desired understanding level 12,13 . This procedure established the final version of the SEFIPwork in the Brazilian Portuguese.

SEFIP-work score
The questionnaire consists of 14 items, each item related to a body part. There are five answers for each item, with scores that range from 0 to 4. Thus, the total score varies between 0 and 56 points; the higher the score, the higher disability 11 . In addition to this total score, we suggest estimating a separate score for each body region to produce a score from 0 (no disability) to 4 (maximum disability). This regionalized score avoids errors in interpreting the magnitude of disability that can be generated by pure analysis of the total score.

Statistical analysis
Descriptive analysis was performed; qualitative variables are presented as absolute numbers (percentage) and quantitative variables as means (standard deviation[SD]). Data processing was performed using SPSS software version 17.0 (Chicago, IL, USA).

RESULTS
After face and content validation, three changes were made to the questionnaire: the answer associated with score 4 was changed from "Não consigo dançar por causa da dor" (I cannot dance because of the pain) to "Não consigo trabalhar por causa da dor" (I cannot work because of the pain); item 13 was changed from "Tornozelos/pés" (ankles/ feet) to "Tornozelos" (ankles), item 14 was changed from "Dedos dos pés" (toes) to "Pés" (feet). Therefore, this version subjected to the face and content validity was considered the pre-final SEFIP-work version. Thirty workers that spoke Brazilian Portuguese as mother tongue answered the questionnaire. The average age of participants was 34.76 years (SD=6.84); 20 (66.66%) participants were men. Table 1 shows other personal and worker characteristics. All participants understood the SEFIP-work items and alternatives, and thus no changes in the pre-final phase were necessary. The average total SEFIP-work score was 6.59 (SD=3.66), with the item "parte inferior das costas" (lower back) being the most marked (n=28; 93.33%), with an average score of 1.18 (SD=0.73). Table 2 shows further details on the results of functional disability and pain measured by SEFIP-work. Figures 1  and 2 show the final version of the SEFIP-work questionnaire in Brazilian Portuguese and English, respectively.   Figure 1. Brazilian Portuguese version of Self-Estimated Functional Inability because of Pain for workers (SEFIP-work)

DISCUSSION
We performed the face and content validity of the SEFIP-work questionnaire for Brazilian workers. This process is the first step in the validation process of this questionnaire, and it will allow its future use to investigate musculoskeletal injuries in this population.
The process of initial validity is usually published as the basis for future studies that focus on the analysis of psychometric properties. In this sense, the methods and objectives of our study are similar to the investigations conducted by Kamonseki, Fonseca and Calixtre 16 , Donat et al. 17 , and De Bortoli et al. 18 . Our study and these investigations [16][17][18] were mainly based on the classics publications of Beaton et al. 12 and Prinsen et al. 13 .
According to a previous study 19 , the understanding of a questionnaire by 80% of the sample included in the pre-final testing phase is acceptable. In our study, 100% of the sample comprehended all SEFIP-work items, statements, and instructions. This result was expected for the questionnaire due to the simple presentation, straight forward structure, and absence of long and interpretive sentences.
"Lower back", followed by "upper back", were the regions with the highest prevalence of musculoskeletal pain. Our sample consisted of workers from various professional fields. Using NMQ, other studies also investigated pain distribution in workers and found similar results: Akodu and Ashalejo 20 identified a greater presence of lower back pain in hospital nurses, López-González, González and González-Menéndez 21 found the highest presence of pain in the neck region of laboratory technicians, and Özdinç et al. 22 observed higher prevalence of pain in the neck and lumbar region of scholars.
Our study has some limitations. Although face and content validity is the first step in the validation process, it alone does not support research or occupational use. Thus, future studies should measure the psychometric properties of the SEFIP-work in Brazilian Portuguese. Moreover, we recommend the translation the SEFIP-work questionnaire and its adaptation to other languages. We present in our article an English version of the SEFIPwork ( Figure 2); however, it has been freely translated. Thus, textual revisions and cross-cultural adaptations must be performed by researchers that speak English as mother tongue. Finally, we include workers from different professional categories, which makes the sample heterogeneous. This fact must be considered when interpreting the results presented here.