Psychometric properties of the Work Limitations Questionnaire applied to nursing workers

Objective: to evaluate the psychometric properties of the Work Limitations Questionnaire and to measure presenteeism in a sample of nursing workers. Method: a cross-sectional study, with non-probabilistic sampling. Data was collected between July 2018 and February 2019 in two high-complexity hospitals, and the sample was composed of 304 participants. The validity analysis of the Work Limitations Questionnaire was performed by means of Confirmatory Factor Analysis. Results: most of the participants were women (88.5%), with a mean age of 40.9 years old. The validities of the factorial, convergent and discriminant construct and the reliability of the complete version and of the 16-item version of the instrument were adequate after adjusting the models to the sample. A statistically significant and negative correlation (p<0.001) was verified between the workload, working time and the Time Management and Physical Demands dimensions; as well as a statistically significant (p<0.001) correlation between working time and the Mental-Interpersonal Demands and Production Demands dimensions. Gender and professional category did not influence presenteeism. The rate of loss of productivity at work was 19.51%. Conclusion: the Work Limitations Questionnaire showed adequate validity and reliability and can be considered a valid and reliable instrument for assessing presenteeism in the nursing team.

in the Northern region of the state of Paraná and the other in the Northwest region of the state of São Paulo, both in municipalities considered references for health treatment and with high population density.
A total of 600 nurses, nursing technicians and assistants working in the aforementioned institutions were invited to participate in the research. The inclusion criteria considered were the following: working for at least six months in the institutions; not being away from work during the data collection period; referring having health problems; and reporting having worked ill in the last two weeks prior to the date of data collection.
The established criteria are based on the theoretical assumptions that supported the elaboration of the WLQ, which consider presenteeism as a phenomenon resulting from health problems that interfere in the individual's working capacity (21,23) .
The minimum sample size was estimated considering the need for five to 10 respondents per parameter to be estimated (25) . As the WLQ has 25 items, 56 parameters were considered (25 items, 25 errors and six correlations between the factors), requiring a minimum sample size of 280 to 560.
A total of 476 workers (adherence rate = 78.6%) agreed to participate in this study. However, according to the inclusion criteria adopted, 172 (36.1%) workers denied having any health problem and having worked ill in the last two weeks, being excluded from the sample.
Thus, the sample was composed of 304 participants.

Data collection
Data collection took place between July 2018 and February 2019. Nursing workers active in all sectors of the two institutions studied in this research were personally invited to participate. The invitation was made individually and during working hours, and up to three attempts were made to approach each worker. All the participants received information about the study and signed an Informed Consent Form (ICF).
After signing the informed consent form, the participants were invited to go to a private room and, in the presence of the researcher, but without interference, they answered the data collection instruments. Everyone had the option to fill out the forms immediately or to answer them at a time they deemed most appropriate; in these cases, a new period for the collection of information was scheduled.

Data collection instruments
To characterize the participants, an instrument was used with demographic and occupational information such as age, gender, marital status, schooling level, professional category, working time in nursing and in the institution, weekly workload, type of employment contract, presence/absence of double employment contract and health conditions of the workers, which was subjected to a validation process by the Expert Committee before being applied (26) .
Regarding the type of employment contract, the following categories were considered: civil servants (represented by the workers who passed To evaluate presenteeism, the Work Limitations Questionnaire (WLQ) was used, an instrument originally developed by Lerner and collaborators (21) in the English language. The WLQ is a self-applicable tool, which asks the participant to assess their own degree of difficulty to perform specific tasks required in their score, there is a manual with guidelines through which it is possible to calculate the global WLQ score and the index of lost productivity at work (16) .
In addition to the original version with 25 items, using the same theoretical bases as the original version, reduced versions of WLQ have also been proposed, such as WLQ-16 (27) and WLQ-8 (28)(29)(30) . Initially, the 16-item version was developed for a study of carpal tunnel syndrome and maintained the four domains of the original version (27) .
The eight-item version was developed based on the eight issues predictive of economic results related to the loss of productivity of the original version (13) . Given its short size, WLQ-8 is commonly used in non-research settings, as a tool for rapid assessment of workers' health (28)(29)(30) .
In Brazil, the WLQ was translated and culturally adapted for the first time in 2007 (10) , being the version used in this study.
It is noted that, for the use of WLQ, authorization was obtained from the Mapi Research Trust, a non-profit organization coordinated by the authors of the original version of the instrument.

Data analysis
Descriptive statistics was used to analyze the data related to the characterization of the participants.
To validate the WLQ, the psychometric sensitivity of the items, the validity of the factorial, convergent and discriminant construct, the validity of divergent and competing criteria, and the reliability of the instrument were estimated.
The psychometric sensitivity of the WLQ items was assessed using summary (mean, median and standard deviation) and form (skewness and kurtosis) measures of the participants' answers, being considered adequate when the absolute values of skewness and kurtosis were below three and seven, respectively, that is, when the distribution of the items did not severely violate normal distribution (31)(32) .
The factorial construct validity was tested by means

Presenteeism scores in the sample
After adjusting the complete WLQ model to the data, the instrument's global score was measured in order to assess the levels of presenteeism in the sample. For this, the guidelines by the authors of the original instrument were followed (21) , with three stages being carried out. In stage 1, the arithmetic means of the WLQ domains were calculated, following Equation 1.
(2).   After data validation, the WLQ scores were calculated for the sample (Table 1).    Table 2 shows that no statistically significant differences were observed between the WLQ scores according to gender and professional category. Table 3 shows the correlation matrix between the domains of the WLQ and the working time in nursing and the workload. to the work of these professionals (3,5) , which was also verified in this study from the participants' reports. In status, exhaustion and reduced productivity (3,22) .
In addition to the physical demands, nursing workers face excessive workloads, unhealthy work environments, This fact corroborates the assumptions of the Demand-Control Model (22) , relating inappropriate work processes to the generation of demands of various natures, which lead to psychological wear out and other health problems in the workers.
A study carried out with nursing workers at an Intensive Care Unit showed that high levels of pressure