Cross-sectional and longitudinal reliability for clinical measurement of attachment loss*

Abstract Progression of marginal periodontitis in humans is characterized by acute exacerbations during short periods of time followed by periods of remission. The analytical procedures used to distinguish actively progressing sites from non-progressing sites within an individual's dentition are controversial. The purpose of the present investigation was to use measurements of probing depth and attachment level from a prospective longitudinal study of episodic periodontal disease progression to examine measurement and diagnostic reliability. In 10 systemically healthy adult human subjects with untreated advanced periodontitis, probing depth and attachment levels were measured at baseline and every 30 days for 10 to 12 months. Measurements were made at 6 sites of each tooth using an acrylic onlay as a reference point and a pressure sensitive probe. Replicate measurements were made on sites showing apparent changes in attachment loss of 2 mm or more in a month, and their contralateral counterparts. Cross-sectional reliability was described by means and standard deviations for the absolute differences between replicate measurements: 0.63 + 0.87 mm for anterior teeth, 0.58 + 0.80 mm for premolars and 0.69 + 0.91 mm for molars. The mean differences tended to decrease with increasing time on study and tended to be greater in deeper pockets. Longitudinal reliability was described by analyzing site-specific serial attachment level measurements across the study time period. Maximum likelihood methods were used to estimate false positive and false negative diagnostic rates associated with the diagnosis of attachment loss based on minimum threshold levels of 1 and 2 mm. The use of a 1 mm threshold resulted in estimated false positive rates of 0.08 to 0.11 and false negative rates of 0.11 to 0.15. The use of a 2 mm threshold resulted in estimated false positive rates of 0.02 to 0.03 and false negative rates of 0.17 to 0.23. The design of clinical studies involving probing measurement of attachment loss should involve consideration of the impact of such error rates.