STATISTICAL PROCEDURES. The scores of alternate versions were computed. The demographic statistics of the sample including age, sex, total score of all included versions of NDI were described by mean, standard deviation (SD), median, interquartile range, minimum and maximum value. We performed the Wilcoxon signed rank test to perform a non-parametric comparison between NDI scores since the total score of NDI-10 was computed from ordinal scale. Agreement of ▇▇▇▇▇ solutions The normal distribution of mean differences of all three comparisons were inspected by the histogram. Using the B&A plots, we summarized the individual agreement between each of the identified NDI versions by the mean difference and the 95% limits of agreement (LoA; ±1.96 times the standard deviation). To test the average agreement and differences between each NDI score, we examined the mean differences by one-sample t-test(▇▇▇▇▇▇▇▇▇, 2015). We reported the sample size for each comparison, the degree of freedom, mean differences with p-value and 95% confidence interval (CI), standard error of differences (SE). Transformations including logarithmic and linear transformations were applied to normalize the non- uniform pattern of the bias on the plot. For instance, when the B&A plot shows a linear relationship between differences and means, (the differences measurement bias start with negative value and then becomes positive while the magnitude of the mean increases), we can regress differences between the methods (D) on the average of the two methods (A) by D = b1 × A + b0. The 95% LoA for the regression should build on the SD of the residual (SDres) from the established model (±1.96 times SDres) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). All analysis was performed by IBM SPSS statistics, Version 25.0 (IBM Corporation, Armonk, NY). We considered a significance level of p ≤ 0.05 as statistically significant. Results Study Selection and NDI version identification Initially, our search yielded 303 publications. After removing the duplications, 296 articles were left. Six studies were then selected for full text review after title and abstract review. Of these, two ▇▇▇▇▇ solutions that met the study criteria were identified from 2 individual studies including a 8-item version NDI (NDI-8) developed by ▇▇▇ ▇▇▇ ▇▇▇▇▇ and colleagues(▇▇▇ ▇▇▇ ▇▇▇▇▇ et al., 2009) which was based on ▇▇▇▇▇ criteria, and a 5-item version NDI (NDI-5) developed by ▇▇▇▇▇▇ and ▇▇▇▇▇▇▇▇▇ (2013) based on conceptual and ▇▇▇▇▇ criteria (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). This allowed 3 B&A comparisons (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs.NDI-5, and NDI-8 vs. NDI-5). The flowchart of studies through the selection process is displayed in Figure 1. Ordinal score transformation Three NDI scores were calculated for each participant. The first NDI score was derived from the original ordinal scale (maximum of 50)(▇▇▇▇▇▇, 2008). We calculated second set of NDI scores according to the 8 item ▇▇▇▇▇ solution provided by ▇▇▇ ▇▇▇ ▇▇▇▇▇ and collogues (▇▇▇ ▇▇▇ ▇▇▇▇▇ et al., 2009), where 2 items (headache and lifting) were removed and then, the ordinal scores were transferred to linear score with the maximum value of 50. For third score transformation, two steps were taken to derive the total score as recommended in a study that considered both conceptual issues and ▇▇▇▇▇ findings(▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). Firstly, 5 functional items regarding person care, concentration, working, driving, and recreation were kept into the total score calculation. A rescoring strategy, was then used to remedy the disordered threshold of driving related item (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). The original score of responses (012345) was re-coded by collapsing the fourth and fifth options (012334), while the original structure (012345) was retained for other 4 items. Therefore, the maximum total score of NDI 5-item version was 24 on the ordinal scale. This score was transformed in to an equivalent ranging from 0 to 50 to enable the direct comparisons (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). Please see Appendix 2 for a summary of transformations. Sample Table 1 describes the demographic information including age, pain intensity, total scores of ▇▇▇-▇▇, ▇▇▇-▇, and NDI-5 and stratified by sex. Thirty-one subjects experienced injury or trauma related neck-pain including car accident, sports injury, and fall. Other conditions leading to neck pain were arthritis, pinched nerves, and disc problems. The normal distribution of the mean differences of comparisons were confirmed by inspecting the histogram. See Figure 2,3,▇▇▇▇ ▇▇▇▇▇▇▇▇ signed rank test revealed statistically significant differences between total scores from each two NDI versions (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs. NDI-5, and NDI-8 vs. NDI-5). See Table 2 Demographic characteristic of the sample Table 1 Male (N=43) Female (N=158) Total (N=201) Mean (SD) Range, max min- Mean (SD) Range, max min- Mean (SD) Range, max min- Median (IQR) Age, year 49.2 19 - 74 45.7 19 - 74 46.5 19 - 74 NA (12.2) (12.8) (12.8) Pain intensity 2.0 (1.4) 0 -5 2.1 (1.2) 0 - 5 2.1 (1.3) 0 - 5 NA NDI-10 14.6 2 – 44 17.0 0 – 41 16.4 0 – 44 15.0 (14.0) (10.7) (9.8) (10.0) NDI-8 17.8 0 – 33 19.0 0 – 31.5 18.4 0 – 32.3 19.2 (8.2) (7.0) (6.0) (6.2) ▇▇▇-▇ ▇▇.▇ ▇ - ▇▇ ▇▇.▇ ▇ - ▇▇ 21.0 0 – 35.0 22.0 (11.0) (8.3) (7.6) (7.8) NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation Min: minimum Max: maximum IQR: Interquartile range Agreement of ▇▇▇▇▇ solutions Table 2 demonstrated both average and individual agreement results of all three comparisons. Through pairwise comparisons, we identified that the mean difference was approximately 10% of the total score between the NDI-10 and NDI-5 (-4.6 points), whereas the ▇▇▇-▇▇ ▇▇▇▇▇▇ ▇▇▇-▇ and NDI-8 versus NDI-5had similar mean differences that were about half (-2.3 points). We considered the NDI-10 as the reference method during comparisons, negative mean differences indicating that both NDI-8 and NDI-5 systematically scored higher than standard NDI-10 The B&A plots displayed wider 95% LoA for the agreement between NDI-10 and NDI-8 (-12.0, 7.4) and NDI-5 (-14.9, 5.8) compared with the agreement between the NDI-8 and NDI-5 (-7.8, 3.3). Through visual inspection of the ▇▇▇▇▇-▇▇▇▇▇▇ plot, the bias between NDI-10 and NDI-8 tended to be in opposite directions at different point in the scale range, as negative value of differences predominated in the lower end (before scores of 20) and positive values predominated in the high end of the scale (between 20 and 40). A similar trend was identified in the comparison between NDI-10 and NDI-5. However, such patterns were not present in the plot comparing NDI-8 with NDI-5. Please see figure 5, 6, 7. The linear relationship on the B&A plot comparing NDI-8 with NDI-5was confirmed by the simple linear regression equation D = -0.2 × A + 2.2 with a significant p value for the over model and regression coefficient (p < 0.001) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). We then plotted 95% LoA based on the SDres which was equal to 2.4 from the regression model. The new upper and lower limited was constructed as D = -0.2 × A + 2.189 ± 1.96 × 2.4. See Figure 8. Table 2 ▇▇▇▇▇-▇▇▇▇▇▇ statistics and non-parametric comparisons by ▇▇▇▇▇▇▇▇ signed rank test Comparison Sample size Degree Individual agreement Average Wilcoxon of agreement signed freedom rank test Mean of difference (d)with (95% CI) SD of difference Upper LoA d+1.96SD Lower LoA d- 1.96SD SE ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -2.3* (-3.0 - -1.6) 5.0 7.4 -12.0 0.4 P<0.001* ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -4.6* (-5.3 - -3.8) 5.3 5.8 -14.9 0.5 P<0.001* ▇▇▇-▇ ▇▇▇-▇ vs. 201 200 -2.3* (-2.7 - -1.9) 2.8 3.3 -7.8 0.2 P<0.001* * significant as p<0.001 NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation SE: standard error base on the mean of difference Discussion We identified two ▇▇▇▇▇ approved versions of the NDI (NDI-8 and NDI-5) through a comprehensive literature review and revealed disagreements in score results within versions (NDI-10 vs. NDI-8 and NDI-5) using B&A plot analysis. (▇▇▇▇▇▇▇▇▇, 2015; ▇▇▇ ▇▇▇ ▇▇▇▇▇ et al., 2009; ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). Such significant differences within versions were identified in non-parametric group comparisons. The wide range of the 95% LoA established surrounding the point estimate of the agreement would threaten the interchangeable application of different versions. When compared the traditional NDI-10 with the 8 items ▇▇▇▇▇ approved version, a difference of ranging from -12.0 to 7.4 units accounting for nearly 15% to 25% of the total score was important for a measurement of 50 units, since 9 units of change would significantly influence the classification of the disability level(▇▇▇▇▇▇, 2008). For example, a participant who obtained a score of 20 on the traditional NDI-10 would be considered to have moderate level of neck disability. However, the LoAs between ▇▇▇▇▇ versions suggest that scores might fall within the mild or severe level a range from -12.0 to 7.4 units. This reflects the extent of misclassification error that might occur on the basis of scoring. The bias between versions was even larger 30% (-14.9 for lower limit) when comparing the NDI-10 with the NDI-5. The differences between NDI-8 and NDI-5 were uniform after linear transformation and were smaller than the discordance between the traditional and ▇▇▇▇▇ scored versions, with a mean variation of 4.7 units (10% of the total score). This smaller difference likely reflects some benefits of a ▇▇▇▇▇ approach, but also some differences related to the number of items included. This smaller error still suggests that these measures cannot be used interchangeably. An advantage of the NDI-8 is that it 8 items may exhibit more range or stability than a 5-item version. Conversely, the NDI-5 is more focused conceptually since it focuses on function, and it reduces respondent burden. Head-to- head comparison of how these two versions performed in measuring clinical outcomes over time are needed to evaluate their relative utility.
Appears in 1 contract
Sources: Neck Disability Index Agreement
STATISTICAL PROCEDURES. The scores of alternate versions were computed. The demographic statistics of the sample including age, sex, total score of all included versions of NDI were described by mean, standard deviation (SD), median, interquartile range, minimum and maximum value. We performed the Wilcoxon signed rank test to perform a non-parametric comparison between NDI scores since the total score of NDI-10 was computed from ordinal scale. Agreement of ▇▇▇▇▇ solutions The normal distribution of mean differences of all three comparisons were inspected by the histogram. Using the B&A plots, we summarized the individual agreement between each of the identified NDI versions by the mean difference and the 95% limits of agreement (LoA; ±1.96 times the standard deviation). To test the average agreement and differences between each NDI score, we examined the mean differences by one-sample t-test(▇▇▇▇▇▇▇▇▇t- test(Giavarina, 2015). We reported the sample size for each comparison, the degree of freedom, mean differences with p-value and 95% confidence interval (CI), standard error of differences (SE). Transformations including logarithmic and linear transformations were applied to normalize the non- non-uniform pattern of the bias on the plot. For instance, when the B&A plot shows a linear relationship between differences and means, (the differences measurement bias start with negative value and then becomes positive while the magnitude of the mean increases), we can regress differences between the methods (D) on the average of the two methods (A) by D = b1 × A + b0. The 95% LoA for the regression should build on the SD of the residual (SDres) from the established model (±1.96 times SDres) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). All analysis was performed by IBM SPSS statistics, Version 25.0 (IBM Corporation, Armonk, NY). We considered a significance level of p ≤ 0.05 as statistically significant. Results Study Selection and NDI version identification Initially, our search yielded 303 publications. After removing the duplications, 296 articles were left. Six studies were then selected for full text review after title and abstract review. Of these, two ▇▇▇▇▇ solutions that met the study criteria were identified from 2 individual studies including a 8-item version NDI (NDI-8) developed by ▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde and colleagues(▇▇▇ ▇▇▇ ▇▇▇▇▇ colleagues(Van Der Velde et al., 2009) which was based on ▇▇▇▇▇ criteria, and a 5-item version NDI (NDI-5) developed by ▇▇▇▇▇▇ and ▇▇▇▇▇▇▇▇▇ MacDermid (2013) based on conceptual and ▇▇▇▇▇ criteria (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). This allowed 3 B&A comparisons (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs.NDI-5, and NDI-8 vs. NDI-5). The flowchart of studies through the selection process is displayed in Figure 1. Ordinal score transformation Three NDI scores were calculated for each participant. The first NDI score was derived from the original ordinal scale (maximum of 50)(▇▇▇▇▇▇, 2008). We calculated second set of NDI scores according to the 8 item ▇▇▇▇▇ solution provided by ▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde and collogues (▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde et al., 2009), where 2 items (headache and lifting) were removed and then, the ordinal scores were transferred to linear score with the maximum value of 50. For third score transformation, two steps were taken to derive the total score as recommended in a study that considered both conceptual issues and ▇▇▇▇▇ findings(▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). Firstly, 5 functional items regarding person care, concentration, working, driving, and recreation were kept into the total score calculation. A rescoring strategy, was then used to remedy the disordered threshold of driving related item (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). The original score of responses (012345) was re-coded by collapsing the fourth and fifth options (012334), while the original structure (012345) was retained for other 4 items. Therefore, the maximum total score of NDI 5-item version was 24 on the ordinal scale. This score was transformed in to an equivalent ranging from 0 to 50 to enable the direct comparisons (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). Please see Appendix 2 for a summary of transformations. Sample Table 1 describes the demographic information including age, pain intensity, total scores of ▇▇▇-▇▇, ▇▇▇-▇, and NDI-5 and stratified by sex. Thirty-one subjects experienced injury or trauma related neck-pain including car accident, sports injury, and fall. Other conditions leading to neck pain were arthritis, pinched nerves, and disc problems. The normal distribution of the mean differences of comparisons were confirmed by inspecting the histogram. See Figure 2,3,▇▇▇▇ ▇▇▇▇▇▇▇▇ 2,3,4The Wilcoxon signed rank test revealed statistically significant differences between total scores from each two NDI versions (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs. NDI-5, and NDI-8 vs. NDI-5). See Table 2 Table 1 Demographic characteristic of the sample Table 1 Male (N=43) Female (N=158) Total (N=201) Mean (SD) Range, max min- Mean (SD) Range, max min- Mean (SD) Range, max min- Median (IQR) Age, year 49.2 (12.2) 19 - 74 45.7 19 - 74 46.5 19 - 74 NA (12.2) (12.8) ▇▇ - ▇▇ ▇▇.▇ (12.8▇▇.▇) Pain ▇▇ - ▇▇ ▇▇ ▇▇▇▇ intensity 2.0 (1.4) 0 -5 2.1 (1.2) 0 - 5 2.1 (1.3) 0 - 5 NA NDI-10 14.6 (10.7) 2 – 44 17.0 (9.8) 0 – 41 16.4 (10.0) 0 – 44 15.0 (14.0) (10.7) (9.8) (10.0) NDI-8 17.8 (7.0) 0 – 33 19.0 (6.0) 0 – 31.5 18.4 (6.2) 0 – 32.3 19.2 (8.2) NDI-5 20.1 (7.08.3) 0 - 35 21.2 (6.07.6) 0 - 33 21.0 (6.27.8) ▇▇▇-▇ ▇▇.▇ ▇ - ▇▇ ▇▇.▇ ▇ - ▇▇ 21.0 0 – 35.0 22.0 (11.0) (8.3) (7.6) (7.8) NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation Min: minimum Max: maximum IQR: Interquartile range Agreement of ▇▇▇▇▇ solutions Table 2 demonstrated both average and individual agreement results of all three comparisons. Through pairwise comparisons, we identified that the mean difference was approximately 10% of the total score between the NDI-10 and NDI-5 (-4.6 points), whereas the ▇▇▇-▇▇ ▇▇▇▇▇▇ ▇▇▇-▇ and NDI-8 versus NDI-5had similar mean differences that were about half (-2.3 points). We considered the NDI-10 as the reference method during comparisons, negative mean differences indicating that both NDI-8 and NDI-5 systematically scored higher than standard NDI-10 The B&A plots displayed wider 95% LoA for the agreement between NDI-10 and NDI-8 (-12.0, 7.4) and NDI-5 (-14.9, 5.8) compared with the agreement between the NDI-8 and NDI-5 (-7.8, 3.3). Through visual inspection of the ▇▇▇▇▇-▇▇▇▇▇▇ plot, the bias between NDI-10 and NDI-8 tended to be in opposite directions at different point in the scale range, as negative value of differences predominated in the lower end (before scores of 20) and positive values predominated in the high end of the scale (between 20 and 40). A similar trend was identified in the comparison between NDI-10 and NDI-5. However, such patterns were not present in the plot comparing NDI-8 with NDI-5. Please see figure 5, 6, 7. The linear relationship on the B&A plot comparing NDI-8 with NDI-5was confirmed by the simple linear regression equation D = -0.2 × A + 2.2 with a significant p value for the over model and regression coefficient coeficient (p < 0.001) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). We then plotted 95% LoA based on the SDres which was equal to 2.4 from the regression model. The new upper and lower limited was constructed as D = -0.2 × A + 2.189 ± 1.96 × 2.4. See Figure 8. Table 2 ▇▇▇▇▇-▇▇▇▇▇▇ statistics and non-parametric comparisons by Wilcoxon signed rank test Discussion We identified two ▇▇▇▇▇ approved versions of the NDI (NDI-8 and NDI-5) through a comprehensive literature review and revealed disagreements in score results within versions (NDI-10 vs. NDI-8 and NDI-5) using B&A plot analysis. (Giavarina, 2015; Van Der Velde et al., 2009; ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇ signed rank test ▇▇, 2013). Such significant differences within versions were identified in non-parametric group comparisons. The wide range of the 95% LoA established surrounding the point estimate of the agreement would threaten the Comparison Sample size Degree of freedom Individual agreement Average Wilcoxon of agreement signed freedom rank test Mean of difference (d)with (95% CI) SD of difference Upper LoA d+1.96SD Lower LoA d- 1.96SD d-1.96SD SE ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -2.3* (-3.0 - -1.6) 5.0 7.4 -12.0 0.4 P<0.001* ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -4.6* (-5.3 - -3.8) 5.3 5.8 -14.9 0.5 P<0.001* ▇▇▇-▇ ▇▇▇-▇ vs. 201 200 -2.3* (-2.7 - -1.9) 2.8 3.3 -7.8 0.2 P<0.001* * significant as p<0.001 NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation SE: standard error base on the mean of difference Discussion We identified two ▇▇▇▇▇ approved versions of the NDI (NDI-8 and NDI-5) through a comprehensive literature review and revealed disagreements in score results within versions (NDI-10 vs. NDI-8 and NDI-5) using B&A plot analysis. (▇▇▇▇▇▇▇▇▇, 2015; ▇▇▇ ▇▇▇ ▇▇▇▇▇ et al., 2009; ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). Such significant differences within versions were identified in non-parametric group comparisons. The wide range of the 95% LoA established surrounding the point estimate of the agreement would threaten the interchangeable application of different versions. When compared the traditional NDI-10 with the 8 items ▇▇▇▇▇ approved version, a difference of ranging from -12.0 to 7.4 units accounting for nearly 15% to 25% of the total score was important for a measurement of 50 units, since 9 units of change would significantly influence the classification of the disability level(▇▇▇▇▇▇, 2008). For example, a participant who obtained a score of 20 on the traditional NDI-10 would be considered to have moderate level of neck disability. However, the LoAs between ▇▇▇▇▇ versions suggest that scores might fall within the mild or severe level a range from -12.0 to 7.4 units. This reflects the extent of misclassification error that might occur on the basis of scoring. The bias between versions was even larger 30% (-14.9 for lower limit) when comparing the NDI-10 with the NDI-5. The differences between NDI-8 and NDI-5 were uniform after linear transformation and were smaller than the discordance between the traditional and ▇▇▇▇▇ scored versions, with a mean variation of 4.7 units (10% of the total score). This smaller difference likely reflects some benefits of a ▇▇▇▇▇ approach, but also some differences related to the number of items included. This smaller error still suggests that these measures cannot be used interchangeably. An advantage of the NDI-8 is that it 8 items may exhibit more range or stability than a 5-item version. Conversely, the NDI-5 is more focused conceptually since it focuses on function, and it reduces respondent burden. Head-to- to-head comparison of how these two versions performed in measuring clinical outcomes over time are needed to evaluate their relative utility.
Appears in 1 contract
Sources: Neck Disability Index Agreement
STATISTICAL PROCEDURES. The scores of alternate versions were computed. The demographic statistics of the sample including age, sex, total score of all included versions of NDI were described by mean, standard deviation (SD), median, interquartile range, minimum and maximum value. We performed the Wilcoxon signed rank test to perform a non-parametric comparison between NDI scores since the total score of NDI-10 was computed from ordinal scale. Agreement of ▇▇▇▇▇ solutions The normal distribution of mean differences of all three comparisons were inspected by the histogram. Using the B&A plots, we summarized the individual agreement between each of the identified NDI versions by the mean difference and the 95% limits of agreement (LoA; ±1.96 times the standard deviation). To test the average agreement and differences between each NDI score, we examined the mean differences by one-sample t-test(▇▇▇▇▇▇▇▇▇t- test(Giavarina, 2015). We reported the sample size for each comparison, the degree of freedom, mean differences with p-value and 95% confidence interval (CI), standard error of differences (SE). Transformations including logarithmic and linear transformations transformation were be applied to normalize the non- non-uniform pattern of the bias on the plot. For instance, when the B&A plot shows a linear relationship between differences and means, (means as the differences or measurement bias start starts with negative value and then becomes become positive while the magnitude of the mean increases), we can regress differences between the methods (D) on the average of the two methods (A) by D = b1 × A + b0. The 95% LoA for the regression should build on the SD of the residual (SDres) from the established model (±1.96 times SDres) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). All analysis was performed by IBM SPSS statistics, Version 25.0 (IBM Corporation, Armonk, NY). We considered a significance level of p ≤ 0.05 as statistically significant. Results Study Selection and NDI version identification Initially, our search yielded 303 publications. After removing the duplications, 296 articles were left. Six studies were then selected for full text review after title and abstract review. Of these, two ▇▇▇▇▇ solutions that met the study criteria were identified from 2 individual studies including a 8-item version NDI (NDI-8) developed by ▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde and colleagues(▇▇▇ ▇▇▇ ▇▇▇▇▇ colleagues(Van Der Velde et al., 2009) which was based on ▇▇▇▇▇ criteria, and a 5-item version NDI (NDI-5) developed by ▇▇▇▇▇▇ and ▇▇▇▇▇▇▇▇▇ MacDermid (2013) based on conceptual and ▇▇▇▇▇ criteria (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). This allowed 3 B&A comparisons (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs.NDI-5, and NDI-8 vs. NDI-5). The flowchart of studies through the selection process is displayed in Figure 1. Ordinal score transformation Three NDI scores were calculated for each participant. The first NDI score was derived from the original ordinal scale (maximum of 50)(▇▇▇▇▇▇, 2008). We calculated second set of NDI scores according to the 8 item ▇▇▇▇▇ solution provided by ▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde and collogues (▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde et al., 2009), where 2 items (headache and lifting) were removed and then, the ordinal scores were transferred to linear score with the maximum value of 50. For third score transformation, two steps were taken to derive the total score as recommended in a study that considered both conceptual issues and ▇▇▇▇▇ findings(▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). Firstly, 5 functional items regarding person care, concentration, working, driving, and recreation were kept into the total score calculation. A rescoring strategy, was then used to remedy the disordered threshold of driving related item (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). The original score of responses (012345) was re-coded by collapsing the fourth and fifth options (012334), while the original structure (012345) was retained for other 4 items. Therefore, the maximum total score of NDI 5-item version was 24 on the ordinal scale. This score was transformed in to an equivalent ranging from 0 to 50 to enable the direct comparisons (▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇MacDermid, 2013). Please see Appendix 2 for a summary of transformations. Sample Table 1 describes the demographic information including age, pain intensity, total scores of ▇▇▇-▇▇, ▇▇▇-▇, and NDI-5 and stratified by sex. Thirty-one subjects experienced injury or trauma related neck-pain including car accident, sports injury, and fall. Other conditions leading to neck pain were arthritis, pinched nerves, and disc problems. The normal distribution of the mean differences of comparisons were confirmed by inspecting the histogram. See Figure 2,3,▇▇▇▇ ▇▇▇▇▇▇▇▇ 2,3,4The Wilcoxon signed rank test revealed statistically significant differences between total scores from each two NDI versions (NDI-10 vs. ▇▇▇-▇, ▇▇▇-▇▇ vs. NDI-5, and NDI-8 vs. NDI-5). See Table 2 2. Demographic characteristic of the sample Table 1 Male (N=43) Female (N=158) Total (N=201) Mean (SD) Range, max min- Mean (SD) Range, max min- Mean (SD) Range, max min- Median (IQR) Age, year 49.2 (12.2) 19 - 74 45.7 19 - 74 46.5 19 - 74 NA (12.2) (12.8) ▇▇ - ▇▇ ▇▇.▇ (12.8▇▇.▇) Pain ▇▇ - ▇▇ ▇▇ ▇▇▇▇ intensity 2.0 (1.4) 0 -5 2.1 (1.2) 0 - 5 2.1 (1.3) 0 - 5 NA NDI-10 14.6 (10.7) 2 – 44 17.0 (9.8) 0 – 41 16.4 (10.0) 0 – 44 15.0 (14.0) (10.7) (9.8) (10.0) NDI-8 17.8 (7.0) 0 – 33 19.0 (6.0) 0 – 31.5 18.4 (6.2) 0 – 32.3 19.2 (8.2) NDI-5 20.1 (7.08.3) 0 - 35 21.2 (6.07.6) 0 - 33 21.0 (6.27.8) ▇▇▇-▇ ▇▇.▇ ▇ - ▇▇ ▇▇.▇ ▇ - ▇▇ 21.0 0 – 35.0 22.0 (11.0) (8.3) (7.6) (7.8) NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation Min: minimum Max: maximum IQR: Interquartile range Agreement of ▇▇▇▇▇ solutions Table 2 demonstrated both average and individual agreement results of all three comparisons. Through pairwise comparisons, we identified that the mean difference was approximately 10% of the total score between the NDI-10 and NDI-5 (-4.6 points), whereas the ▇▇▇-▇▇ ▇▇▇▇▇▇ ▇▇▇-▇ and NDI-8 versus NDI-5had similar mean differences that were about half (-2.3 points). We considered the NDI-10 as the reference method during comparisons, negative mean differences indicating that both NDI-8 and NDI-5 systematically scored higher than standard NDI-10 The B&A plots displayed wider 95% LoA for the agreement between NDI-10 NDI- 10 and NDI-8 (-12.0, 7.4) and NDI-5 (-14.9, 5.8) compared with the agreement between the NDI-8 and NDI-5 (-7.8, 3.3). Through visual inspection of the ▇▇▇▇▇-▇▇▇▇▇▇ plot, the bias between NDI-10 and NDI-8 tended to be in opposite directions at different point in the scale range, as negative value of differences predominated in the lower end (before scores of 20) and positive values predominated in the high end of the scale (between 20 and 40). A similar trend was identified in the comparison between NDI-10 and NDI-5. However, such patterns were not present in the plot comparing NDI-8 with NDI-5. Please see figure 5, 6, 7. The linear relationship on the B&A plot comparing NDI-8 with NDI-5was confirmed by the simple linear regression equation D = -0.2 × A + 2.2 with a significant p value for the over model and regression coefficient coeficient (p < 0.001) (▇▇▇▇▇ & ▇▇▇▇▇▇, 1999). We then plotted 95% LoA based on the SDres which was equal to 2.4 from the regression model. The new upper and lower limited was constructed as D = -0.2 × A + 2.189 ± 1.96 × 2.4. See Figure 8. Table 2 ▇▇▇▇▇-▇▇▇▇▇▇ statistics and non-parametric comparisons by ▇▇▇▇▇▇▇▇ Wilcoxon signed rank test Comparison Sample size Degree Individual agreement Average Wilcoxon of agreement signed freedom rank test Mean of difference (d)with (95% CI) SD of difference Upper LoA d+1.96SD Lower LoA d- 1.96SD SE ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -2.3* (-3.0 - -1.6) 5.0 7.4 -12.0 0.4 P<0.001* ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -4.6* (-5.3 - -3.8) 5.3 5.8 -14.9 0.5 P<0.001* ▇▇▇-▇ ▇▇▇-▇ vs. 201 200 -2.3* (-2.7 - -1.9) 2.8 3.3 -7.8 0.2 P<0.001* * significant as p<0.001 NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation SE: standard error base on the mean of difference Discussion We identified two ▇▇▇▇▇ approved versions of the NDI (NDI-8 and NDI-5) through a comprehensive literature review and revealed disagreements in score results within versions (NDI-10 vs. NDI-8 and NDI-5) using B&A plot analysis. (▇▇▇▇▇▇▇▇▇Giavarina, 2015; ▇▇▇ ▇▇▇ ▇▇▇▇▇ Van Der Velde et al., 2009; ▇▇▇▇▇▇ & ▇▇▇▇▇▇▇▇▇, 2013). Such significant differences within versions were identified in non-parametric group comparisons. The wide range of the 95% LoA established surrounding the point estimate of the agreement would threaten the interchangeable application of different versions. When compared the traditional NDI-10 with the 8 items ▇▇▇▇▇ approved version, a difference of ranging from -12.0 to 7.4 units accounting for nearly 15% to 25% of the total score was important for a measurement of 50 units, since 9 units of change would significantly influence the classification of the disability level(▇▇▇▇▇▇, 2008). For example, a participant who obtained a score of 20 on the traditional NDI-10 would be considered to have moderate level of neck disability. Comparison Sample size Degree of freedom Individual agreement test Mean of difference SD of difference Upper LoA d+1.96SD Lower LoA d-1.96SD SE ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -2.3* (-3.0 - -1.6) 5.0 7.4 -12.0 0.4 P<0.001* ▇▇▇-▇▇ ▇▇▇-▇ vs. 201 200 -4.6* (-5.3 - -3.8) 5.3 5.8 -14.9 0.5 P<0.001* ▇▇▇-▇ ▇▇▇-▇ vs. 201 200 -2.3* (-2.7 - -1.9) 2.8 3.3 -7.8 0.2 P<0.001* * significant as p<0.001 NDI-10: The total score of NDI 10-item (original) version on ordinal scale with maximum of 50 points. NDI-8: The total score of NDI 8-item version on linear scale with maximum of 50 points. NDI-5: The total score of NDI 5-item version on linear scale with maximum of 50 points. SD: standard deviation SE: standard error base on the mean of difference However, the LoAs between ▇▇▇▇▇ versions suggest that scores might fall within the mild or severe level a range from -12.0 to 7.4 units. This reflects the extent of misclassification error that might occur on the basis of scoring. The bias between versions was even larger 30% (-14.9 for lower limit) when comparing the NDI-10 with the NDI-5. The differences between NDI-8 and NDI-5 were uniform after linear transformation and were smaller than the discordance between the traditional and ▇▇▇▇▇ scored versions, with a mean variation of 4.7 units (10% of the total score). This smaller difference likely reflects some benefits of a ▇▇▇▇▇ approach, but also some differences related to the number of items included. This smaller error still suggests that these measures cannot be used interchangeably. An advantage of the NDI-8 is that it 8 items may exhibit more range or stability than a 5-item version. Conversely, the NDI-5 is more focused conceptually since it focuses on function, and it reduces respondent burden. Head-to- to-head comparison of how these two versions performed in measuring clinical outcomes over time are needed to evaluate their relative utility.
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Sources: Neck Disability Index Agreement