[Intraclass correlation coefficient]

The intraclass correlation coefficient makes it possible to measure the general concordance between two or more measurements that involve variables of a quantitative nature, obtained with different measuring instruments or evaluators. It is based on an analysis of variance model with repeated measures. Its use is only possible if there is normality of the distributions of the variables, equality of variances and independence between the errors produced by the observers.

Reproducibility of manual choroidal thickness measurements using optical coherence tomography

PURPOSE

Spectral-domain optical coherence tomography (SD-OCT) is the most useful tool to measure choroidal thickness (CT). CT may be increased in ocular and systemic diseases. However, there are concerns relating reproducibility and external validity of OCT. The aim of this study was to assess the inter-observer and intra-observer variability of manual OCT measurements.

METHODS

CT was manually measured in the central choroid of 40 eyes from 21 subjects (11 healthy and 10 with ankylosing spondylitis) using RTVue-100 OCT (Optovue Inc., Fremont, CA, EE.UU.). Measurements were performed by 9 independent ophthalmologists from 6 different centers. To assess the inter-observer variability, the intra-class correlation coefficient (ICC) method was calculated. Also, intra-observer variability was assessed in 2 of the ophthalmologists.

RESULTS

The mean subfoveal CT was 364.9±85.1μm (range, 170 to 572). The inter-observer ICC was 0.823 (CI 95%, 0.749 to 0.888, p<0.001). The intra-observer ICCs were 0.885 (CI 95%, 0.783 to 0.939, p<0.001) and 0.925 (CI 95%, 0.859 to 0.960. p<0.001).

CONCLUSIONS

In this study, manual measurements of CT with OCT showed a good concordance. These results suggest that manual OCT is a valid tool for multicenter studies.