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Hand-held dynamometry in patients with haematological malignancies: measurement error in the clinical assessment of knee extension strength.

Knols RH, Aufdemkampe G, de Bruin ED, Uebelhart D, Aaronson NK - BMC Musculoskelet Disord (2009)

Bottom Line: The SDDs for the generated parameters varied from 17.23 Nm (11.04% of GM) to 27.26 Nm (17.09% of GM) for intra-observer measurements, and 26.76 Nm (16.77% of GM) to 31.62 Nm (18.66% of GM) for inter-observer measurements, with similar results for the limits of agreement.The results indicate that there is acceptable relative reliability for evaluating knee strength with a HHD, while the measurement error observed was modest.The HHD may be useful in detecting changes in knee extension strength at the individual patient level.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Switzerland. ruud.knols@usz.ch

ABSTRACT

Background: Hand-held dynamometry is a portable and inexpensive method to quantify muscle strength. To determine if muscle strength has changed, an examiner must know what part of the difference between a patient's pre-treatment and post-treatment measurements is attributable to real change, and what part is due to measurement error. This study aimed to determine the relative and absolute reliability of intra and inter-observer strength measurements with a hand-held dynamometer (HHD).

Methods: Two observers performed maximum voluntary peak torque measurements (MVPT) for isometric knee extension in 24 patients with haematological malignancies. For each patient, the measurements were carried out on the same day. The main outcome measures were the intraclass correlation coefficient (ICC +/- 95%CI), the standard error of measurement (SEM), the smallest detectable difference (SDD), the relative values as % of the grand mean of the SEM and SDD, and the limits of agreement for the intra- and inter-observer '3 repetition average' and the 'highest value of 3 MVPT' knee extension strength measures.

Results: The intra-observer ICCs were 0.94 for the average of 3 MVPT (95%CI: 0.86-0.97) and 0.86 for the highest value of 3 MVPT (95%CI: 0.71-0.94). The ICCs for the inter-observer measurements were 0.89 for the average of 3 MVPT (95%CI: 0.75-0.95) and 0.77 for the highest value of 3 MVPT (95%CI: 0.54-0.90). The SEMs for the intra-observer measurements were 6.22 Nm (3.98% of the grand mean (GM) and 9.83 Nm (5.88% of GM). For the inter-observer measurements, the SEMs were 9.65 Nm (6.65% of GM) and 11.41 Nm (6.73% of GM). The SDDs for the generated parameters varied from 17.23 Nm (11.04% of GM) to 27.26 Nm (17.09% of GM) for intra-observer measurements, and 26.76 Nm (16.77% of GM) to 31.62 Nm (18.66% of GM) for inter-observer measurements, with similar results for the limits of agreement.

Conclusion: The results indicate that there is acceptable relative reliability for evaluating knee strength with a HHD, while the measurement error observed was modest. The HHD may be useful in detecting changes in knee extension strength at the individual patient level.

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Distribution from Bland and Altman; average of 3 MVPT values for inter-observer measurements. Five data points are outside the ± 1.96 standard deviation boundaries. The ± 1.96 standard deviation boundaries represent approximately 21.29 Nm below and 11.51 Nm above the mean, which is -4.89 Nm.
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Figure 3: Distribution from Bland and Altman; average of 3 MVPT values for inter-observer measurements. Five data points are outside the ± 1.96 standard deviation boundaries. The ± 1.96 standard deviation boundaries represent approximately 21.29 Nm below and 11.51 Nm above the mean, which is -4.89 Nm.

Mentions: The absolute reliability of the SEM, the SDD, and the relative values as % of the grand mean of the SEM and SDD are presented in Tables 2 and 3. The 95% limits of agreement according to the method of Bland and Altman are presented in Figures 2, 3, 4, 5. The ANOVA for repeated measures yielded no significant changes (p > 0.05) between the three MVPT strength measurements, indicating that there were no learning effects from the first to the third measurements for the intra- and inter-tester observers. There were no significant differences in muscle strength between the intra- and inter-observer sessions for the average of 3 MVPT measurements (Tables 4 + 5) or for the highest value of 3 MVPT measurements (Tables 6 + 7).


Hand-held dynamometry in patients with haematological malignancies: measurement error in the clinical assessment of knee extension strength.

Knols RH, Aufdemkampe G, de Bruin ED, Uebelhart D, Aaronson NK - BMC Musculoskelet Disord (2009)

Distribution from Bland and Altman; average of 3 MVPT values for inter-observer measurements. Five data points are outside the ± 1.96 standard deviation boundaries. The ± 1.96 standard deviation boundaries represent approximately 21.29 Nm below and 11.51 Nm above the mean, which is -4.89 Nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2662793&req=5

Figure 3: Distribution from Bland and Altman; average of 3 MVPT values for inter-observer measurements. Five data points are outside the ± 1.96 standard deviation boundaries. The ± 1.96 standard deviation boundaries represent approximately 21.29 Nm below and 11.51 Nm above the mean, which is -4.89 Nm.
Mentions: The absolute reliability of the SEM, the SDD, and the relative values as % of the grand mean of the SEM and SDD are presented in Tables 2 and 3. The 95% limits of agreement according to the method of Bland and Altman are presented in Figures 2, 3, 4, 5. The ANOVA for repeated measures yielded no significant changes (p > 0.05) between the three MVPT strength measurements, indicating that there were no learning effects from the first to the third measurements for the intra- and inter-tester observers. There were no significant differences in muscle strength between the intra- and inter-observer sessions for the average of 3 MVPT measurements (Tables 4 + 5) or for the highest value of 3 MVPT measurements (Tables 6 + 7).

Bottom Line: The SDDs for the generated parameters varied from 17.23 Nm (11.04% of GM) to 27.26 Nm (17.09% of GM) for intra-observer measurements, and 26.76 Nm (16.77% of GM) to 31.62 Nm (18.66% of GM) for inter-observer measurements, with similar results for the limits of agreement.The results indicate that there is acceptable relative reliability for evaluating knee strength with a HHD, while the measurement error observed was modest.The HHD may be useful in detecting changes in knee extension strength at the individual patient level.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Rheumatology and Institute of Physical Medicine, University Hospital Zurich, Switzerland. ruud.knols@usz.ch

ABSTRACT

Background: Hand-held dynamometry is a portable and inexpensive method to quantify muscle strength. To determine if muscle strength has changed, an examiner must know what part of the difference between a patient's pre-treatment and post-treatment measurements is attributable to real change, and what part is due to measurement error. This study aimed to determine the relative and absolute reliability of intra and inter-observer strength measurements with a hand-held dynamometer (HHD).

Methods: Two observers performed maximum voluntary peak torque measurements (MVPT) for isometric knee extension in 24 patients with haematological malignancies. For each patient, the measurements were carried out on the same day. The main outcome measures were the intraclass correlation coefficient (ICC +/- 95%CI), the standard error of measurement (SEM), the smallest detectable difference (SDD), the relative values as % of the grand mean of the SEM and SDD, and the limits of agreement for the intra- and inter-observer '3 repetition average' and the 'highest value of 3 MVPT' knee extension strength measures.

Results: The intra-observer ICCs were 0.94 for the average of 3 MVPT (95%CI: 0.86-0.97) and 0.86 for the highest value of 3 MVPT (95%CI: 0.71-0.94). The ICCs for the inter-observer measurements were 0.89 for the average of 3 MVPT (95%CI: 0.75-0.95) and 0.77 for the highest value of 3 MVPT (95%CI: 0.54-0.90). The SEMs for the intra-observer measurements were 6.22 Nm (3.98% of the grand mean (GM) and 9.83 Nm (5.88% of GM). For the inter-observer measurements, the SEMs were 9.65 Nm (6.65% of GM) and 11.41 Nm (6.73% of GM). The SDDs for the generated parameters varied from 17.23 Nm (11.04% of GM) to 27.26 Nm (17.09% of GM) for intra-observer measurements, and 26.76 Nm (16.77% of GM) to 31.62 Nm (18.66% of GM) for inter-observer measurements, with similar results for the limits of agreement.

Conclusion: The results indicate that there is acceptable relative reliability for evaluating knee strength with a HHD, while the measurement error observed was modest. The HHD may be useful in detecting changes in knee extension strength at the individual patient level.

Show MeSH
Related in: MedlinePlus