Reproducibility of a clinical screening method for assessing gingival inflammation, pockets and plaque retentions

The purpose of this study was to evaluate the reproducibility of the Periodontal Treatment Need System (PTNS), when plaque retentions were examined separately. A sample of 8000 persons was drawn to represent the Finnish population aged 30 yr and over. The first clinical examination (total sample) was made by a specially trained expanded-duty dental auxiliary (EDDA). During the second examination (2-6 months later), 20% of the total sample was reexamined by a dentist, and of those, every 6th patient was examined by the EDDA. Reproducibility of the PTNS was assessed as intra- and interexaminer agreement and was calculated using Cohen's kappa and weighted kappa. The intraexaminer weighted kappa values were 0.67 +/- 0.05 for the PTNS and 0.48 +/- 0.15 for plaque retentions. The interexaminer weighted kappa values between the PTNS registrations were 0.77 +/- 0.05 and 0.74 +/- 0.12 in plaque retentions when examinations were made within 1 day, and 0.53 +/- 0.05 and 0.37 +/- 0.07, respectively, when the interexaminer registrations were made with an interval of 2-6 months between them. The kappa values for intra- and interexaminer reliability reflect quite high reproducibility.