Morphometric Optical Imaging of Microporated Nail Tissue: An Investigation of Intermethod Agreement, Reliability, and Technical Limitations

BACKGROUND AND OBJECTIVES: While optical imaging is a useful technique to quantitate morphological differences and treatment effects, comparative investigations of the various techniques are lacking. This study aimed at evaluating intermethod agreement, reliability, and technical limitations of wide-field microscopy (WFM), reflectance confocal microscopy (RCM), and optical coherence tomography (OCT) for morphometry by assessing fractionally ablated nail tissue.

STUDY DESIGN/MATERIALS AND METHODS: Fifty healthy nail clippings were processed with a fractionated CO2 -laser (20 mJ/microbeam, density 15%), measured with calipers, and imaged using WFM, OCT, and RCM. Images were assessed for nail plate thickness, micropore dimensions, degree of poration, and artifacts. Repeated measurements (2-5) were taken to evaluate method repeatability using Cronbach's α and coefficients of variation (CoV), and estimate the intermethod correlation through linear correlation assessment (Pearson correlation coefficient [PCC]), ranked correlation (Kendall's tau; tau-c), and intraclass correlation (Shrout-Fleiss reliability coefficient; ICC).

RESULTS: The repeatability varied substantially between methods and target measurements. The level of intermethod agreement for thickness measurements performed with calipers, WFM, and OCT was high (tau-c ≥ 0.7; ICC ≥ 0.8; PCC ≥ 0.9). RCM could only image 28 out of 50 samples due to its limited penetration depth. OCT demonstrated the highest repeatability of all imaging techniques (CoV 4-7%) and nail thickness showed the highest measurement reliability (α = 0.92). Micropore dimensions correlated strongest between OCT and RCM (tau-c/ICC/PCC ≥ 0.5). All modalities were prone to artifacts, which may have adversely affected measurement variation and intermethod agreement.

CONCLUSION: Intermethod agreement and reliability appear to be highly dependent on the specific modality and target measurement. To reap the benefits of each technique while mitigating their limitations, an integrated approach to optical imaging is recommended. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.