Is change in probing depth a reliable predictor of change in clinical attachment loss?

Background: Clinicians and researchers need a measure for monitoring the periodontal condition of their patients or study participants. The authors explored the utility of change in probing depth (PD) for predicting change in clinical attachment loss (CAL). Methods: The authors used clinical trial data from 363 participants who had received nonsurgical treatment to describe associations between PD and CAL changes. They computed the association between PD and CAL changes-correlation, sensitivity, specificity, and positive and negative predictive values-according to tooth type, tooth site and initial PD. Results: Depending on the subset of tooth sites, sensitivity of PD change to predict CAL change ranged from 18 to 74 percent; the highest sensitivity was at initially deep sites. Specificity and negative predictive value were higher than sensitivity and positive predictive value. Correlations between person-level mean PD and CAL changes ranged from 0.60 to 0.79 and were highest at initially deep sites. Conclusions: Except at initially deep sites, PD change did not reliably predict CAL change. Clinicians and researchers who measure only PD may fail to identify teeth that lose or gain attachment. Clinical Implications: Clinicians should consider monitoring CAL to detect changes in periodontal status more reliably. It is unknown if these findings apply to patients treated surgically or to prediction of tooth loss.