Identification and consequences of distinct Löe-Silness gingival index examiner styles for the clinical assessment of gingivitis.
BACKGROUND
In clinical studies, gingivitis is most frequently assessed by the Löe-Silness gingival index (GI). The objective of this work was to develop an understanding of how clinicians experienced with GI differ with respect to how they apply GI and to assess the impact of different examination styles on statistical outcomes and magnitude of treatment differences.


METHODS
A method was developed to mathematically relate the average GI score and degree of bleeding observed for a subject. Graphical analyses were used to profile examiner styles with respect to using the GI index. A prospective single-center, examiner-blind study comparing the effects of a staggered prophylaxis on gingivitis was then conducted, where a difference in gingivitis was created between two balanced groups by providing subjects a prophylaxis at two staggered time points. Subjects were assigned to one of two cohorts; within each cohort, group 1 subjects received a dental prophylaxis following the baseline examination and group 2 subjects received a dental prophylaxis 8 weeks later. Five to 7 days after the group 2 prophylaxis, all subjects were examined for GI. Twelve experienced clinicians participated.


RESULTS
Retrospective analyses indicated the presence of distinct examiner styles which are based on the frequency that a given GI score (0, 1, 2, or 3) is measured by a clinician. In the prospective study, all 12 examiners observed statistically significant differences between the prophylaxis treatment groups at the final visit for both mean number of bleeding sites and mean GI; the magnitude ranged from 21.5% to 84.6% for mean number of bleeding sites and 9.4% to 39.2% for mean GI. There were 4 distinct styles employed by these experienced clinicians.


CONCLUSIONS
Varying examiner styles impact the structure of resulting data. Importantly, the implementation of arbitrary thresholds (e.g., 20%) regarding percent treatment differences between groups as a guideline for judging the clinical significance is scientifically unsupported. A more scientific criterion in the field of gingivitis clinical testing would be the independent demonstration of statistical superiority compared to a negative control and/or a demonstration of similar or superior efficacy to clinically proven positive controls. In addition, interexaminer calibration is a mechanism that can be utilized to minimize the impact of different examiner styles in clinical settings involving more than one examiner.
McClanahan
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Procter and Gamble Company, Mason, OH 45040-9462, USA.
Bartizek
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Biesbrock
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D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002138:Calibration; D015331:Cohort Studies; D003777:Dental Prophylaxis; D005260:Female; D005884:Gingival Hemorrhage / Q000145:classification / Q000628:therapy; D005891:Gingivitis / Q000145:classification* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010512:Periodontal Index; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016037:Single-Blind Method; D013223:Statistics as Topic; D016896:Treatment Outcome