Single item presenteeism question: Reliability and validity of Persian version in participants with low back pain

Abstract

BACKGROUND:

Single item presenteeism question (SIPQ) is a rating scale to assess the impact of low back pain (LBP) on presenteeism.

OBJECTIVE:

To translate the SIPQ into Persian language (SIPQ-P) and evaluate the reliability and validity of the SIPQ-P in participants with LBP.

METHODS:

In the first stage, the English SIPQ was translated into Persian language in a cross-sectional design following standard forward-backward approach with expert panel review and pilot testing. In the second stage with a prospective cohort design, 100 participants with LBP (84 male and 16 female, mean age±SD: 33.9±11.2 years) participated. Participants were asked to answer the SIPQ-P and rate their LBP from 0 to 10 according to the numerical pain rating scale (NPRS) for concurrent criterion validity. To evaluate the convergent construct validity of SIPQ, participants completed Persian Functional Rating Index (PFRI). For the divergent validity, the Spearman’s correlation test was used to evaluate the association between the SIPQ-P and education. For the test-retest reliability, 50 participants answered the SIPQ-P after 7 days. Fifty healthy participants (mean age±SD: 24.24±8.07 years) answered the SIPQ-P for evaluating discriminant validity.

RESULTS:

There was a significant difference between the SIPQ-P score of participants and the healthy participants (p < 0.001). The concurrent criterion validity was demonstrated by a significant correlation between the SIPQ-P and pain NPRS (Spearman’s rho = 0.46, p < 0.001). The Spearman correlation coefficient showed a significant correlation between the SIPQ-P scores and the Persian FRI (r = 0.56, p < 0.001). There was no correlation between the SIPQ-P score and the education level (r = –0.001, p = 0.99). The ICC_agreement was 0.77 indicating a very good test-retest reliability.

CONCLUSIONS:

This study showed that the Persian version of SIPQ is a reliable and valid scale to assess the effect of LBP on presenteeism in Persian speakers with LBP.

Keywords

Single item presenteeism question musculoskeletal disorders productivity assessment Persian language

1 Introduction

Low back pain (LBP) is one of the most common musculoskeletal disorders (MSDs) that affects nearly 600 million people globally [1 –4]. About 10%–28% of LBP may become chronic persisting for more than 12 weeks [5, 6]. MSDs including LBP affect the routine functions [7]. LBP has been stated as the leading cause of disability [8, 9]. It follows that the burden of LBP on function and work status can be enormous.

The impact of LBP on work capacity and participation of patients is important in terms of productivity and costs at the social level [10]. The decrease in productivity in patients with LBP can be from work absenteeism or limitation in work with low quantity and quality while the patient is physically present at work (presenteeism) [11, 12].

In the United States, a study has estimated the cost for annual losses of productivity from LBP-related work absence is $28 billion [13]. The costs of presenteeism are even significantly higher than those of absenteeism [14, 15]. Therefore, the effects of presenteeism on work disability should be emphasized and measured using appropriate scales.

There are different multi-item self-report tools to assess the impact of MSDs on presenteeism [10] among which the Work Productivity and Activity Impairment Questionnaire [16], Work Limitation Questionnaire [17], and Health and Work Performance Questionnaire [18] are in common use. But, these instruments despite being reliable and valid [19] have limitations: they are long which increases the burden on patients and clinicians; they have items not relevant to the occupation; and their interpretation is not easy [20]. Consequently, global single-item measures in particular the Single-Item Presenteeism Questions (SIPQs) have been advocated and used in various investigations [21 –23] for simplicity, easy scoring and interpretation, and finally reduced demand.

The Single Item Presenteeism Question (SIPQ) is the adapted version of the standardized World Health Organization HPQ questionnaire [24] for low back pain asking respondents one question “To what extent has back pain affected your performance at work over the past 30 days?”; and the respondents are further asked to rate their performance at work from 0 = not at all to 10 = extremely worst [25]. The adapted SIPQ has been recently demonstrated that it is a valid and responsive instrument for assessing the impact of LBP on presenteeism in patients with LBP [25]. However, the SIPQ is in English and for use in another language must be translated and adapted first. To our knowledge, the SIPQ is not available in Persian language. Therefore, the present study aimed to translate and adapt the SIPQ to Persian language and to investigate the validity and reliability of the Persian language version of the SIPQ in participants with LBP. The priori hypotheses were that the SIPQ-P would discriminate participants with LBP and healthy participants, and would have good correlation with pain (concurrent criterion validity) and disability (convergent construct validity) measures. As well, we hypothesized that there would be no significant correlation between the SIPQ-P score and the education level for examining divergent construct validity.

2 Method

2.1 Study design

This study used a cross-sectional design to translate and adapt the SIPQ to Persian language. The reliability and validity of the Persian SIPQ was then evaluated using a prospective cohort design. The study protocol was approved by the review board, School of Rehabilitation, and the Ethical Committee of Tehran University of Medical Sciences (TUMS). All participants gave their written informed consent after an explanation about the study aims.

2.2 Participants

Participants with LBP persistant for more than one month, aged ≥18 years and willing to volunteer for the study were included. The exclusion criteria was the presence of any disorders other than LBP affecting their working ability.

2.3 Translation and cultural adaptation of the SIPQ

The English SIPQ was translated to the Persian language following a standard procedure [26] used previously [27 –32]. Briefly, the English version of the SIPQ was forward translated independently by two bilingual translators (T1 and T2). An expert committee with three physiotherapists, one experienced methodologist, and both translators reviewed the translations and produced a synthetized Persian SIPQ (T12). Another two English translators back translated the synthetized Persian version into English language (BT1 and BT2). The expert committee and all the translators reviewed the documents and approved the pre-final Persian SIPQ.

The pre-final Persian SIPQ was pilot tested with 60 individuals (30 healthy participants and 30 participants with LBP). The individuals answered the questions and commented on if the Persian SIPQ was clear and understandable. Subsequently, the expert committee established the final version of the Persian SIPQ (SIPQ-P) for psychometric testing (Appendix).

2.4 Psychometric testing of Persian SIPQ

The patients were recruited from musculoskeletal physiotherapy clinics in Tehran, Iran. A sample of 100 participants with LBP [33] were recruited and answered the SIPQ-P, a 0–10 numerical pain rating scale (NPRS) [34], and the Persian Functional Rating Index (FRI) [35]. Fifty healthy participants answered the SIPQ-P for discriminant validity evaluation. For test-retest reliability, 50 participants (a sub-sample of the initial group of 100 with LBP) completed the SIPQ-P with an interval of 1 to 2 weeks between the first and second measures.

2.5 Statistical analysis

Descriptive statistics of mean±SD or median (interquartile range) were used to describe the characteristics of participants and outcome measures. The frequency of the lowest or highest possible score on the SIPQ-P were calculated for floor or ceiling effects with ≥15% as significant. The discriminant validity of SIPQ-P was analyzed using the Mann-Whitney U test. The concurrent criterion validity and convergent as well as divergent construct validity of the SIPQ-P were analyzed using Spearman rank correlation test with NPRS, Persian FRI, and education, respectively. The correlation coefficients were interpreted as: excellent 1.0 to 0.81; very good 0.80 to 0.61; good 0.60 to 0.41; fair 0.40 to 0.21; and poor.20 to 0.00 [35]. To determine the test-retest reliability of SIPQ-P, the intra-class correlation coefficient (ICC _agreement, two-way random effects model, average measure) was used. An ICC value of a minimum of 0.7 was considered acceptable The statistical analyses were performed with SPSS software version 18.0 (SPSS, Inc, IL).

3 Results

One hundred participants with LBP (84 male/16 female, age 33.9±11.2 years; duration 45.5±65.9 months; education 13.4±3.9 years) and 50 healthy participants (48 male/2 females, age 24.2±8.1 years; education 14.7±1.6 years) completed the study. Fifty participants (from the initial 100) were re-tested (47 males/3 females; age 30.4±9.1 years; education 13.2±3.0 years; duration 38.5±54.9 months).

In participants with LBP (n = 100), the median (interquartile range, IQR) for SIPQ-P was 5.0 (3.0–6.75). For the 50 participants who participated in the test-retest reliability phase of the study, the median SIPQ-P was 4.5 (IQR = 3.0–6.0) for test and 4.0 (IQR = 2.0–6.0) for retest.

3.1 Cross-cultural adaptation

The SIPQ was successfully translated and adapted into Persian language. Forward and Back translation encountered no problems and the SIPQ-P corresponded well with the original English one. The expert committee agreed on the pre-final as well as the final version of the SIPQ-P. Pre-testing revealed no difficulties in understanding the SIPQ-P. The participants with LBP reported no ambiguities in the SIPQ-P.

3.2 Floor and ceiling effects

For test (n = 100), six persons achieved the lowest score 0.0 and seven persons achieved the highest score 10.0. For retest (n = 50), three persons achieved the lowest score 0.0 and two persons achieved the highest score 10.0.

3.3 Discriminant validity

The Mann-Whitney U test showed a significant difference in SIPQ scores between participants with LBP (median = 4.5, IQR = 3.0–6.0) who participated in test-retest reliability phase of the study and healthy participants (median = 0.0, IQR = 0.0–1.25) (Z = –7.43, p < 0.001).

3.4 Concurrent criterion validity

There was a significant correlation between the Persian SIPQ scores and the pain intensity NPRS (Spearman’s rho = 0.46, p < 0.001).

3.5 Construct validity

The correlation between the Persian SIPQ scores and the Persian FRI (40.85±18.24;7.5–95.0) for convergent construct validity was statistically significant (r = 0.56, p < 0.001). There was no statistically significant correlation between the SIPQ-P score and the education for divergent construct validity (r = –0.001, p = 0.99).

3.6 Test-retest reliability

The ICC_agreement for the SIPQ-P was 0.77, with 95 % CI 0.60–0.87, p < 0.001.

4 Discussion

This translation and cultural adaptation of SIPQ into Persian language and subsequent validation analysis supports the reliability and validity of the Persian SIPQ for use in Persian-speaking countries. The validation findings, together with the results of test-retest reliability analysis, convergent as well as divergent construct validity, and discriminant analysis, support the possible use of Persian SIPQ to assess the effects of LBP on work presenteeism in clinical and research settings. The validity findings of the SIPQ-P in this study is consistent with the original English version [25] indicating that the SIPQ-P instrument measures what it is expected to assess. The present study is the first to use and validate the SIPQ instrument into Persian language in Iranian Persian-speaking adults with LBP.

4.1 Clinical utility

Consistent with the original English version [25] all participants in this study responded to the SIPQ-P. This indicates the utility and acceptability of the SIPQ-P. Reasons for this finding could be that the SIPQ-P as a single item measure is simple to administer, requires a short time to respond, is not tiresome for respondents, and from the ethical point of view minimizes participant burden [37]. Additionally, the SIPQ-P was translated easily indicating the potential for further adaptability of the SIPQ to different cultures.

4.2 Floor and ceiling effects

Participants in this study were asked to rate their performance at work on the 10-point SIPQ-P scale. The end-points on the SIPQ-P selected by the participants did not reach the 15% cut-off for floor or ceiling effect. The absence of floor or ceiling effects indicates the content validity and the ability of the SIPQ-P to detect changes over time [31]. The responsiveness of the SIPQ-P was not studied in this study to evaluate whether it is able to detect the effects of interventions in a population with LBP. However, the responsiveness of the original English SIPQ [25] together with the lack of floor or ceiling effects found in this study indicates the SIPQ-P is likely to be responsive in clinical situations to demonstrate improvements or worsening after an intervention. The floor and ceiling effects were not reported for the original English version [25].

4.3 Discriminant validity

As expected, discriminant validity was observed in the current study when looking specifically at median scores of the participants with LBP and healthy participants (4.5 vs 0.0). The SIPQ-P discriminated between participants with self-reported impact of LBP on presenteeism and healthy participants without LBP. The ability of the SIPQ-P to discriminate between groups (LBP vs healthy participants) may derive from the specificity of the single item question related to the impact of LBP on presenteeism. The English SIPQ has shown known group validity to discriminate among subgroups of patients with different intensity levels of LBP [25].

4.4 Concurrent criterion validity

In this study, the impact of pain on presenteeism was assessed in adult participants with LBP. Hence, the NPRS was considered as a criterion for evaluation of concurrent criterion validity. The significant good correlation between the two measures demonstrates criterion validity of the SIPQ-P. However, an excellent correlation was not obtained between the SIPQ-P and the NPRS. One possibility for this finding could be that short scales and in particular single item measures may not have better criterion related validity than the long scales due to the error variance [38]. Additionally, the correlation between SIPQ-P and NPRS construct may not be expected to exceed the reliability of the test considering the 95% CI obtained for the test-retest reliability of the SIPQ-P [38]. One further reason could be the number of patients recruited for this study. We included 100 patients as recommended by the guidelines [33]. A large number of patients may demonstrate excellent correlation between the two measures evaluated in this study. Presenteeism for the original English SIPQ was found to correlate with average pain intensity (r_Pearson = 0.53–0.77; EuroQol-5D pain; r_Spearman = 0.29–0.58) [25].

4.5 Construct validity

Convergent construct validity of SIPQ-P scores was evaluated by Spearman rank correlation test coefficient with the disability measure of FRI. The SIPQ-P instrument demonstrated construct given the significant good correlation with the Persian FRI. However, the correlation was not excellent in describing the impact of LBP on presenteeism. The Persian FRI used for evaluating the construct validity is a multiple item instrument. Multiple item instruments when compared to a single item measure may have superior content validity as they represent all subfacets constituting the construct [39]. Nevertheless, a significant good correlation was observed. As expected, convergent validity of SIPQ-P was exhibited in the positive direction with higher scores indicating worse outcomes. A good correlation between the SIPQ-P and the Persian FRI indicates that related domains were evaluated, and the SIPQ-P scores reflect an accurate construct of presenteeism. The acceptable “good” level of construct validity demonstrated through this study complements the information regarding the concurrent criterion validity of the SIPQ-P with pain, suggesting that the SIPQ-P provides a valid measure of presenteeism and functional impairments emanated from low back pain. For the original English SIPQ, association between the SIPQ and the Roland-Morris Disability Questionnaire (RMDQ) ranged between 0.53–0.70 [25].

The divergent construct validity was determined by a nonsignificant correlation between the SIPQ-P score and education. As hypothesized, there was no significant correlation between presenteeism in terms of SIPQ-P score and education suggesting the divergent construct validity of the SIPQ-P.

In the current study, standard presenteeism tools were not used for assessing the SIPQ-P validity, either construct validity or concurrent criterion validity. For future investigations, the standard questionnaires specifically developed for presenteeism must be used to examine the SIPQ-P validity.

4.6 Test-retest reliability

The SIPQ-P exceeded the ICC threshold of 0.70, indicating high test-retest reliability. The validity demonstrated through this study (concurrent criterion validity and construct validity) complements the information regarding test-retest reliability of the SIPQ-P in the study population with LBP. The test-retest reliability is a component of validity. Together, test-retest reliability, construct validity, and concurrent criterion validity data suggest that the SIPQ-P instrument provides a valid measure of presenteeism in patients with LBP. Test-retest reliability of the SIPQ-P reveals the stability of the scores over time when using the SIPQ-P as an outcome measure in patients with LBP. The reliability of the SIPQ-P provides evidence that this measure is suitable for use in clinical practice and research in the future in the Persian-speaking adult patients with LBP. The test-retest reliability was not evaluated for the original English SIPQ [25].

4.7 Limitations

The study has limitations that need to be noted. First, the SIPQ-P is validated in participants with LBP, thus it is not generizable to other health conditions associated with presenteeism [40]. Second, the SIPQ-P consistent with the original English version [25] was not examined against the multi-item Presenteeism Scales for convergent construct validity. However, studies have found that some single item measures are psychometrically sound [38] and that strong correlations between a single-item question and a multi-item index can and do exist [41]. Third, the responsiveness of the SIPQ-P to determine the ability to detect changes following interventions was not evaluated. However, we expect the SIPQ-P should have the same responsiveness as the original English version [25].

5 Conclusion

The presenteeism resulting from low back pain is important. The annual costs of presenteeism are significant. As well, it can decrease the productivity of patients with LBP. Single item presenteeism question (SIPQ) is a scale to assess the impact of LBP on presenteeism. The present study showed the SIPQ-P has good reliability and validity in Persian-speaking participants with LBP. The SIPQ-P demonstrated clinical utility, lack of floor and ceiling effects, ability to discriminate between LBP and healthy participants, both construct and divergent validity, and concurrent criterion validity. Given that the SIPQ-P is not time consuming, simple to use and interpret, clinicians and researchers across the globe can use it in research and clinical settings to assess presenteeism in Persian-speaking patients with LBP.

Conflict of interest

None to report.

Footnotes

Appendix:

Persian single item presenteeism question (SIPQ-P)

Acknowledgments

This research was supported by Research Deputy of Tehran University of Medical Sciences.

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