Evaluation Of Inter-rater And Test-retest Reliability For Near-infrared Spectroscopy Reactive Hyperemia Measures

Abstract

Near-Infrared spectroscopy (NIRS) is a non-invasive tool used to measure blood flow in peripheral tissues. More information on test-retest reliability and inter-rater agreement of NIRS-based reperfusion assessments is needed. PURPOSE: To assess inter-rater agreement for NIRS based data analysis, and evaluate the measurement’s reliability across days. METHODS: On three separate days, participants’ (N=15 males, 22± 2 yr,) reactive hyperemia was measured in the left gastrocnemius muscle using Continuous-Wave NIRS. A blood pressure cuff was placed proximal to the knee and inflated to occlude lower leg blood flow for 5 minutes. The cuff was rapidly deflated, and the blood flow responses were measured until values returned to baseline. Raw NIRS data were exported and analyzed in a custom-written routine in MATLAB by two individuals. The following NIRS parameters were selected:(1) the time for the O2Hb signal to reach 50% peak post-occlusion hyperemia (T1/2), (2) The O2Hb range used to normalize the NIRS signal; (3) the post peak-hyperemic O2Hb recovery slope, taken as an index of sustained microvascular dilation. Inter-rater agreement was assessed using Intraclass Correlation Coefficients (ICC), calculated using an absolute agreement two-way mixed effects model. 95% confidence intervals (CI) of ICCs are reported. Cronbach’s alpha was used to assess day to day reliability for each of the measures. RESULTS: The ICC data indicate that there is “good” to “excellent” agreement between NIRS analyzers as shown in table 1.The Cronbach’s alpha for raters 1 and 2 were: T1/2 (α =.89, α = .91), O2Hb (α =.95, α = .89), and post peak-hyperemic O2Hb recovery slope (α =.74, α = .83). CONCLUSION: Our data indicate multiple raters can be used to analyze NIRS based reperfusion measures with good agreement and that the method has sufficient test-retest reliability to use in experimental designs involving multiple laboratory visits.