The Caries Assessment Spectrum and Treatment (CAST) instrument: construct validation.

The Caries Assessment Spectrum and Treatment (CAST) is a newly developed epidemiological instrument. The aim of this study was to investigate its construct validity. Four calibrated examiners, using CAST codes 0-6, visually examined 109 surfaces of extracted and exfoliated teeth. These teeth were then hemisectioned, photographed, and assessed histologically by two calibrated examiners using the Downer criteria. Twenty-eight of the 109 teeth were scanned using micro-computed tomography (micro-CT) and assessed by the same examiners using the same criteria. Validation was determined through calculation of the sensitivity, specificity, and Youden index for two categories of carious lesions examined visually, with histology and micro-CT as gold standards. Interexaminer consistency was κ = 0.76: SE ± 0.05 between visual and histological assessments of teeth and was κ = 0.89: SE ± 0.08 between visual and micro-CT assessments. For the category 'healthy' vs. 'diseased' (CAST codes 0-2 vs. CAST codes 3-6), sensitivity, specificity, and Youden index values of 100%, 92.9%, and 93%, respectively, for micro-CT, and 96.6%, 86%, and 83%, respectively, for histology, were obtained. For the category 'dentine' vs. 'non-dentine lesions' (CAST codes 0-3 vs. CAST codes 4-6) sensitivity, specificity, and Youden index values of 90%, 100%, and 90%, respectively, for micro-CT, and 81.4%, 100%, and 81%, respectively, for histology, were obtained. Construct validity of the CAST instrument was obtained.