The effect of awareness of measurement error on physical therapists' confidence in their decisions

Repeatability of position sense measurements in persons with osteoarthritis of the knee: a pilot study

Several reports have described a position sense deficit in persons with osteoarthritis of the knee. For purposes of future comparison, this study determined the agreement between serial measurements of knee position sense conducted over a 10-day period for eight persons of mean age 67.87 ± 7.36 years with stable knee-joint disease. The knee angles used to determine position sense were recorded in the seated position using a potentiometer. The outcome measure was the mean absolute error between five set angles and their matching angles. The intra-class correlation coefficients (ICCS) used to assess reliability of the mean absolute error measurements within and between sessions ranged from 0.57 to 0.52 with an average standard error of measurement of 1.18 degrees. It is concluded that while fairly reliable, clinicians should interpret changes in knee position sense of less than 2.31 degrees carefully in these patients before concluding that a true improvement or deterioration in their knee positioning accuracy has occurred.

Peg Restrained Intrinsic Muscle Evaluator (PRIME): development, reliability, and normative values of a device to quantify intrinsic hand muscle strength in children

PURPOSE

There is a need for objective measures of pediatric intrinsic hand muscle strength as the current standard, the manual muscle test, lacks sensitivity to clinically important changes in muscle strength. We report the development, reliability, and normative values of the Peg Restrained Intrinsic Muscle Evaluator (PRIME), a device that quantifies intrinsic hand muscle strength.

METHODS

Typically developing children, ages 4 to 16 years (n = 119), established normative values of intrinsic strength for thumb palmar abduction, thumb opposition, and index and small finger abduction. A subset of 30 children (15 boys, 15 girls), ages 7 to 16 years, determined inter-rater and intra-rater reliability. We calculated mean, standard deviation, intraclass correlation coefficients, and smallest detectable differences.

RESULTS

Normative results indicate that gender and age were significant predictors of strength. Although the dominant hand generated higher strength measurements on average, differences were not statistically significant. Mean index and small finger abduction strength was significantly lower than thumb abduction and opposition in both genders. Intraclass correlation coefficients ranged from 0.85 to 0.94 for inter-rater reliability and 0.88 to 0.98 for intra-rater reliability. Bland-Altman plots showed an even distribution across the zero line.

CONCLUSIONS

The PRIME device is a reliable tool for the quantification of intrinsic hand muscle strength in children. Age-specific and gender-specific normative values in typically developing children can serve as a future resource for clinicians treating pediatric hand or neuromuscular conditions.

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

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.

Reliability of ambulatory walking activity in patients with hematologic malignancies

OBJECTIVES

To determine the relative and absolute reliability of the assessment of ambulatory walking activity during 2 consecutive weeks in patients with hematologic malignancies recovering at home from their medical treatment and to compare the physical activity level of hematologic cancer patients after high-dose chemotherapy with healthy subjects.

DESIGN

Test-retest study of 2 consecutive 7-day recordings using the microprocessor-based step accelerometer 3 (SAM3).

SETTING

Home and community.

PARTICIPANTS

Patients (n=23) with hematologic malignancies recovering from high-dose chemotherapy and healthy controls (n=30).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The intraclass correlation coefficient (ICC(3,1)) and its 95% confidence interval (CI), SE of measurement procedure and its 95% CI, the smallest detectable difference (SDD), the coefficient of variation (CV), and t tests for the variables total steps and peak activity.

RESULTS

The day-to-day and week-to-week CVs for walking activity and peak activity were 35.17% and 13.17% and 18.61% and 6.90%, respectively. For relative reliability, the ICCs for 2 consecutive 7-day recordings including the 95% CI for total steps and peak activity were 0.90 (95% CI, 0.75-0.98) and 0.85 (95% CI, 0.66-0.94), respectively. The absolute reliability for total steps and peak activity including the SE of measurement procedure and the 95% CI were 564 (95% CI, +/-1106) and 2.42 steps (95% CI, +/-4.74), respectively, for 2 consecutive 7-day recordings. The week-to-week SDD was 1564 for total steps and 6.70 for peak activity. The 7-day mean for total step activity was 5355 for the patients with hematologic malignancies and 6364 for healthy subjects (P<0.05).

CONCLUSIONS

The results of this study indicate that there is good relative reliability for the assessment of 2 consecutive 7-day recordings of ambulatory walking activity, and it showed that the SDD derived from this sample may be useful in detecting changes in daily walking activity in hematologic cancer patients who are recovering from intensive medical treatment. The study also documented compromised levels of ambulatory walking activity among hematologic cancer patients recovering from high-dose chemotherapy as compared with healthy controls.

Reliability of tendon excursion measurements in patients using a color Doppler imaging system

PURPOSE

The purpose of this study was to assess the test-retest reliability of tendon excursion measurements with color Doppler imaging in patients with flexor tendon injuries following a modified Kleinert protocol.

METHODS

One observer performed repeated measurements at 3 different time periods in 13 patients with flexor tendon injuries, following a modified Kleinert protocol. The intraclass correlation coefficient (ICC), the standard error of measurement (SEM), and related indices of measurement error were calculated.

RESULTS

Measurements at 10 day after surgery had an ICC of.88 and an SEM of 1.1 mm. Measurements at 6 weeks after surgery had an ICC of.58 and an SEM of 2.0 mm. The measurements after 3 months had an ICC of.94 and an SEM of 1.2 mm.

CONCLUSION

Measurements at 10 days and more than 3 months after surgery were reliable and were as reliable as the measurements performed on healthy subjects. At 6 weeks after surgery the measurements were less reliable. Color Doppler imaging is a reliable and noninvasive method to assess tendon excursion, even in patients with small tendon excursion movements.

Isometric muscle force measurement for clinicians treating patients with osteoarthritis of the knee

OBJECTIVE

To evaluate the discriminant validity and, for clinicians, the test-retest reliability of isometric force in patients with knee osteoarthritis (OA).

METHODS

Mean isometric muscle strength data collected for 113 patients with knee OA were compared with published normative data for 131 asymptomatic subjects.

RESULTS

Patients with knee OA, ages 60-79 years, could attain only 40-53% of the knee extensor force and 35-46% of the knee flexor force generated by their age- and sex-matched peers. One-week test-retest intraclass correlations ranged from 0.79 to 0.95. Random measurement error demonstrated a favorable "signal-to-noise" ratio.

CONCLUSION

The similar decrease in knee extensor and knee flexor strength demonstrated by patients with knee OA compared with their age- and sex-matched asymptomatic peers suggests that strategies should be directed at both muscle groups to optimally limit joint damage. Isometric muscle force measurement can be a useful assessment tool for clinicians.

Evaluation of impaired fingertip texture discrimination and wrist position sense in patients affected by stroke: comparison of clinical and new quantitative measures

Discriminative sensory loss is common following stroke but may not be adequately detected by routine clinical measures. Quantitative tests of texture discrimination and limb position sense have been recently developed. These tests provide reliable estimates of discrimination, differentiate impaired performance following stroke, and have standardized criteria of abnormality. The purpose of this study was to compare predictions of impairment based on current clinical measures with predictions based on these quantitative, standardized measures. Thirty-five patients who had strokes were tested on the new quantitative measures and clinical measures of texture discrimination and limb position sense. The findings indicated poor agreement between impairment defined using current clinical measures and statistically abnormal performance on the new quantitative, norm-referenced measures. The findings suggest that the quantitative tests may provide additional assessment information to supplement that of the existing clinical measures of texture discrimination and limb position sense. Further development of these new quantitative measures is indicated.

The smallest detectable difference of mandibular function impairment in patients with a painfully restricted temporomandibular joint

Mandibular functions such as speech, laughing, yawning, mastication, and taking a large bite may be impaired if temporomandibular disorders exist. The Mandibular Function Impairement Questionnaire is a validated instrument that scores perceived difficulty of representative mandibular functions in relation to jaw complaints. However, the reliability of the Mandibular Function Impairment Questionnaire has never been adequately tested. Generalizability and decision studies are currently proposed to assess the reliability of a measurement device. The smallest detectable difference is the smallest statistically significant amount of change to be detected with a measurement device. The purpose of this study was to assess the reliability of the Mandibular Function Impairement Questionnaire in terms of the smallest detectable difference. Twenty-five consecutive patients with painfully restricted temporomandibular joints completed the Mandibular Function Impairement Questionnaire on two separate measurement days, one week apart, using two consecutive sessions per day. Spearman's r was calculated for test-retest reliability. Variance components such as patients, measurement days, repetitions, and all their interactions were analyzed in the generalizability study. In the decision study, the smallest detectable difference was calculated for different days and repetitions. Spearman's r varied from 0.69 to 0.96. The between-patient variance and the error variance contributed 81% and 19% to total variance, respectively. The Mandibular Function Impairment Questionnaire is a reliable instrument for the assessment of mandibular function impairment. The minimal amount of change to be detected is 14 units on a scale of 0 to 68. Reliability in terms of the smallest detectable difference increases if the measurement is repeated twice on two separate days: The smallest detectable difference improves to 10 units.

Lumbosacral position sense during pelvic tilting in men and women without low back pain: test development and reliability assessment

STUDY DESIGN

A single group test-retest design to evaluate the reproducibility of lumbosacral position sense measurements.

OBJECTIVES

To develop a measure of position sense in the lumbosacral area and to determine test-retest reliability.

BACKGROUND

Proprioception, muscle control, and coordination training could be the key issues in resolving neuromuscular dysfunction in patients with low back pain, but there are no standard ways to assess these parameters.

METHODS AND MEASURES

A piezoresistive accelerometer attached to the skin over the sacrum was used to research the repositioning accuracy of active pelvic tilting, between days, of 14 young nonimpaired subjects (20 to 26 years of age) in standing.

RESULTS

The mean absolute error for repositioning accuracy (the difference between criterion and matching positions) was 1.81 degrees (+/- 0.85). The intraclass correlation coefficient between measurements obtained on days 1 and 2 was moderate (R = 0.51). The average standard error of measurement associated with the intraclass correlation coefficient was 0.5 degree (95% confidence interval = +/- 0.99 degree).

CONCLUSIONS

These findings suggest that the proposed test is sensitive with moderate test-retest reliability to examine lumbosacral position sense in healthy subjects. Further adjustments in the testing protocol are needed to improve the test-retest reliability.

Smallest detectable difference in outcome variables related to painful restriction of the temporomandibular joint

The smallest detectable difference is the smallest statistically significant change in measurement results. In the field of temporomandibular disorders, the smallest detectable difference is not a commonly used concept. Most outcome studies are based on comparisons of group means, although this does not provide information about individual changes or about the clinical relevance thereof. The smallest detectable difference for maximal mouth opening was calculated from previously published reliability coefficients and the standard deviations of different samples of healthy subjects and patients with complaints of the temporomandibular joint. The smallest detectable difference of pain intensity measured with different visual analogue scales was calculated from the reliability coefficients and standard deviations of a heterogeneous group of pain patients. The smallest detectable difference of function impairment was calculated for a group of patients with complaints of the temporomandibular joint. For maximal mouth opening in healthy subjects, the smallest detectable difference was 5 mm. Repeated measurements improved it to 3 mm. The smallest detectable difference on a visual analogue scale was 28 mm for actual pain intensity and 22 mm for minimal pain as well as for maximal pain intensity. For total function impairment of patients with complaints of the temporomandibular joint, the smallest detectable difference was 8 units on a 0 to 68 scale.

Reliability assessment of isometric knee extension measurements with a computer-assisted hand-held dynamometer

OBJECTIVE

To assess clinically relevant indexes of measurement error of hand-held dynamometer measurements using a computer-assisted hand-held dynamometer (CAHN-DY).

DESIGN

In separate sessions, different physical therapists performed repeated measurements of maximal isometric knee extension.

SETTING

Four physical therapy practices and outpatient departments.

PATIENTS

Consecutive samples of 30 male and 28 female patients aged 13 to 77 years, with isolated orthopedic knee disorders participated in this study.

MAIN OUTCOME MEASURES

For intrarater and interrater applications, the standard error of measurement (SEM) and related 95% confidence intervals and minimal detectable changes were assessed.

RESULTS

Sixty percent of the patients performed within the therapist's upper force limit. Variance between sessions performed by the same or different therapists accounted for a large percentage of the measurement error (70% to 81%). For single measurements, the standard error of measurement was assessed not to exceed 10N x m. Minimal detectable changes for different designs varied from 13.8 to 28.2N x m.

CONCLUSIONS

The CAHN-DY facilitated standardization of test performance in a satisfactory manner, resulting in less measurement error compared with simple hand-held dynamometry.

Reliability and validity of self-paced walking time measures for knee osteoarthritis

This study assessed the reliability and validity of self-paced walking time as an outcome measure for osteoarthritis (OA) of the knee. The 13-m timed walking tests were carried out twice on two separate occasions for 15 patients using photocells. Validity was examined by comparing the walking time data with results of other methodologies for evaluating osteoarthritic gait. As indicated by intra- and inter-day intraclass correlation coefficients of 0.97 and 0.88 the gait measurements were reliable. The measurements also compared favorably with a validated subjective functional index for knee OA (P < 0.01). The findings suggest that measurements of self-paced walking time can provide both reliable and valid data for evaluating functional performance in this patient population.