Construct Validity of Functional Capacity Evaluation in Patients with Whiplash-Associated Disorders

Abstract

Purpose The construct validity of functional capacity evaluations (FCE) in whiplash-associated disorders (WAD) is unknown. The aim of this study was to analyse the validity of FCE in patients with WAD with cultural differences within a workers’ compensation setting. Methods 314 participants (42 % females, mean age 36.7 years) with WAD (grade I and II) were referred for an interdisciplinary assessment that included FCE tests. Four FCE tests (hand grip strength, lifting waist to overhead, overhead working, and repetitive reaching) and a number of concurrent variables such as self-reported pain, capacity, disability, and psychological distress were measured. To test construct validity, 29 a priori formulated hypotheses were tested, 4 related to gender differences, 20 related associations with other constructs, 5 related to cultural differences. Results Men had significantly more hand grip strength (+17.5 kg) and lifted more weight (+3.7 kg): two out of four gender-related hypotheses were confirmed. Correlation between FCE and pain ranged from −0.39 to 0.31; FCE and self-reported capacity from −0.42 to 0.61; FCE and disability from −0.45 to 0.34; FCE and anxiety from −0.36 to 0.27; and FCE and depression from −0.41 to 0.34: 16 of 20 hypotheses regarding FCE and other constructs were confirmed. FCE test results between the cultural groups differed significantly (4 hypotheses confirmed) and effect size (ES) between correlations were small (1 hypothesis confirmed). In total 23 out of 29 hypotheses were confirmed (79 %). Conclusions The construct validity for testing functional capacity was confirmed for the majority of FCE tests in patients with WAD with cultural differences and in a workers’ compensation setting. Additional validation studies in other settings are needed for verification.

Association between social factors and performance during functional capacity evaluations: A systematic review

“…Both studies found differences in FCE performance associated with participant's mother language groups in the German canton of Switzerland (German and non-German) and United States (English and non-English). The study comparing primary German and non-German language speakers evidenced that the German-speaking group performed consistently higher on all FCE tests included in the study, i.e., handgrip strength, waist-tooverhead lift, and overhead work and repetitive reaching task [29]. The study comparing primary English and non-English language speakers evidenced that the English-speaking group showed a moderately higher percentage of valid performance effort (70.2%), with respect to the non-English-speaking group (27.3%) [28].…”

“…There was moderate quality of evidence that higher previous job salary was significantly associated with larger distance walked in the 6MWT [25]. There was low or very low quality of evidence that patients not involved in compensation [19,21] and/or litigation [19] processes, and healthy participants tested after a day's work [24] performed significantly better on FCE tests; also, patients with differences in the instruction [27] and in their primary or mother language [28,29], and both patients and healthy participants with different ethnicity [28,31], had significantly different FCE performances. There was an absence of association of workplace social support reported by patients and healthy participants [22,26] and the different environmental conditions, in which FCE was undertaken [20], with FCE performance.…”

“…The results of the quality assessment for the included articles are displayed in Table 2. Overall, nine articles showed high methodological quality [21][22][23][24][25][26][29][30][31], three showed moderate methodological quality [20,27,28], and one showed low methodological quality [19]. The main limitations found were: unclear study design to answer the research question, incomplete description of sampling strategy, reduced reproducible objective criteria of the measurements, sample size appropriateness, insufficient results details, and estimates of the main results.…”

“…Eleven social or environmental factors were identified. Six involved patients: compensation status [19,21], litigation status [19], country of FCE [23], previous job salary [25], type of instructions [27], and primary or mother language [28,29]; three involved healthy participants: environmental conditions [20], time of day (workday) [24], and examiner's fear behavior [30]; and two involved both populations: self-reported workplace social support [22,26] and ethnicity [28,31]. In addition to this, many social characteristics were gathered such as education level, employment situation, and work experience.…”

“…The results of the quality of evidence assessment for the included articles are displayed in Table 5. Overall, the level of evidence for the factors studied in patients was high for country of FCE [23], moderate for previous job salary [25], low for litigation status [19] and type of instruction [27], and very low for compensation status [19,21] and primary or mother language [28,29]. In healthy participants, the level of evidence for the factors studied was high for examiner's fear behavior [30], and very low for time of day (workday) [24] and environmental conditions [20].…”