HSC Section 6 Nov2016 Green Book

Croake et al

priori significance level of α = .05 ( df = 1, F = 5.71, P = .054). This indicated that vocal intensity may play a role in LEMG signal reliability. No interaction effects between intensity and time factors were found. To further evaluate the reliability of LEMG signals across the 3 testing days, ICCs using a 2-factor mixed ran- dom effect model were calculated. Average measures from 6 sample trials per participant were compared across the 3 testing sessions to evaluate reliability. The ICCs across Sessions 1 through 3 were 0.56 for the 65 dB condition and 0.40 for the 75 dB condition. These between-session ICCs were low, suggesting an interpretation of poor to, at best, fair reliability across testing sessions. Although not stan- dardized, typical calculated values for ICC interpretation are as follows: less than 0.40 = poor reliability, 0.40 to 0.75 = fair to good reliability, and greater than 0.75 = excel- lent reliability. 19 In addition, the SEM was calculated. The SEM was then used to determine the MDC in microvolts necessary to demonstrate a true difference if the muscle was tested on multiple days with 95% confidence boundaries. Results indicated that a change of 51µV would be necessary to determine a true difference in LEMG activity between testing sessions. Numerical results of ICC, SEM, and MDC are presented in Table 5. Intraclass correlations for within- session data revealed strong reliability among participants ranging from 0.84 to 0.95 and from 0.88 to 0.98 for the 65 dB and 75 dB conditions, respectively. Comparisons of within-session data are located in Table 6. Discussion The use of clinical in-office LEMG has been incorporated into the diagnostic routine for the evaluation and treatment of voice disorders in many practices across the country. 8 Although some evidence supports LEMG use in the Table 6.  Intraclass Correlation Coefficients (ICCs) for Within- Session Data. Within-Session ICC Session 1 Session 2 Session 3 65 dB 0.95 0.93 0.84 75 dB 0.88 0.84 0.98 Table 5.  Intraclass Correlation Coefficients (ICCs) Between Sessions, Standard Error of Measurement (SEM), and Minimum Detectable Change (MDC) in µV Necessary to Detect True Change Between Measurements. ICC Sessions 1–3 SEM Sessions 1–3 MDC in µV @ 70% Confidence MDC in µV @ 95% Confidence 65 dB 0.56 18.57 26.26 51.47 75 dB 0.40 23.0 32.5 63.7

diagnosis and prognosis of certain neuromuscular disorders, the general reliability of the LEMG signal in normal partici- pants has not been carefully evaluated. This study measured the reliability of the LEMG signal in normal, vocally healthy participants over time with the central aim of determining if significant LEMG signal variance occurred as a function of multiple testing sessions. Our second aim was to determine if vocalization intensity affected the LEMG signal. In limb studies, control over the degree of muscle contraction is nec- essary to achieve results that are comparable within and across participants. Both maximal and submaximal contrac- tions have been shown to demonstrate strong reliability in limb muscle. 20 We used vocal intensity as a method to con- trol laryngeal muscle contraction levels among participants. Our results indicated that between-session LEMG reliability was poor to fair and that control of vocal intensity may be an important performance variable to help improve the reliabil- ity of these measurements. This study mirrored the University of Iowa head and neck protocol for LEMG diagnostics. 21 In addition to this basic protocol, we used vocal intensity control and a Faraday booth to reduce ambient electrical noise to improve the fidelity of the data and provide the optimal set of cir- cumstances under which to perform our LEMG clinical evaluation. The intent of this study was not to quantify LEMG precisely but rather to use quantitative means to measure LEMG in an ideal environment to test the hypoth- esis that clinical LEMG data are variable across testing ses- sions even with added control parameters in place. Repeated measures analysis of variance indicated a non- significant effect for time of testing, suggesting that LEMG signals for pooled data did not vary significantly across test- ing sessions. Intraclass correlation coefficient analysis for within-session reliability was considered excellent for both intensity conditions ranging from 0.84 to 0.95 and from 0.88 to 0.89 for the 65 dB and 75 dB conditions, respec- tively. However, the between-session ICC revealed poor to fair reliability for both intensity conditions. It should be noted that the most qualitatively consistent data from our study were collected when the participants vocalized at 65 dB, indicating a less reliable measure at greater loudness levels. Data from Sessions 1 and 2 at 65 dB represented the strongest reliability association with an R 2 value of 0.048. This indicated poor reliability even across the most consis- tent recording sessions (see Figures 1 and 2). Reliability debates concerning the clinical usefulness of LEMG for diagnostic and prognostic applications have been raised. 1 According to a recent evidence-based review and clinical recommendations, LEMG data have been con- sidered questionable for clinical uses such as diagnosing paresis/paralysis from joint fixation, for accuracy diagnos- ing diseases of the neuromuscular junction, and for provid- ing accurate diagnostic information of neuropathic and myopathic disorders. 1,8 To address these questions, it has

59