Development, Validation, and Assessment of the Diagnostic Accuracy of a Questionnaire for Periodontitis Screening

The present multicenter cross-sectional clinical study aims at validateing the Italian version of one of the most widely used epidemiological questionnaires for periodontitis screening: the CDC/AAP questionnaire \[hereafter referred to as CDC/AAP\_ITA\]. Furthermore, the study aims at developing a modified version of the CDC/AAP\_ITA questionnaire, enriched with additional questions, and to assess its diagnostic accuracy \[hereafter referred to as QSIdP\].

All procedures included in the study protocol will be conducted in full compliance with the latest version of the Declaration of Helsinki. Participation in the study will require the signing of an informed consent form by each enrolled participant. In addition, the study will adhere to the STARD (Standards for Reporting Diagnostic Accuracy) guidelines.

Following development and validation, the CDC/AAP\_ITA questionnaire (consisting of 8 questions) and the QSIdP questionnaire (consisting of 10 questions) will be administered to 495 patients with heterogeneous periodontal conditions recruited from ten Italian university clinical centers and/or public health facilities. Among these, Unità Complessa di Odontoiatria, Azienda Unità Sanitaria Locale (A.U.S.L.) of Ferrara (Director: Prof. Leonardo Trombelli), will be the Coordinating Center.

Within each center, patients will be enrolled according to specific inclusion criteria (i.e., age ≥18 years, ability to read and understand Italian, willingness to participate in the study) and exclusion criteria (i.e., completely edentulous individuals, subjects who have taken antibiotics within the past 3 months, pregnant women, or individuals with contraindications to periodontal probing).

Patient selection will take place during their stay in the waiting area of each participating clinical center, regardless of their chief complaint. Therefore, the questionnaires will be administered to all first-visit patients (and not exclusively to those seeking periodontal assessment).

Participants enrolled in the study will be asked to complete both the CDC/AAP\_ITA and QSIdP questionnaires without external assistance. Each questionnaire will be identified by an alphanumeric code composed of the center's identifier and a progressive number. Only the principal investigator at each clinical center will hold the list linking patient names to their corresponding alphanumeric codes, thereby ensuring complete data de-identification.

Upon completion of the CDC/AAP\_ITA and QSIdP questionnaires, participants will undergo a full-mouth periodontal clinical examination aimed at recording the following clinical parameters: probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BoP%). Demographic information (age, sex, body mass index), medical history (diabetes, other systemic diseases), and smoking habits will be retrieved from the patient's clinical record. In cases where this information is missing or outdated (more than six months), it will be reconfirmed with the patient. When available, radiographic information will also be integrated into the clinical data.

The clinician responsible for recording clinical parameters will then formulate a periodontal diagnosis according to two different classification systems:

i) Page \& Eke, the reference standard for epidemiological studies; and ii) Tonetti et al. case definition for periodontitis.

The association between self-reported measures of periodontal disease (derived from the questionnaires) and clinical diagnosis (derived from the periodontal examination) will be analyzed using logistic regression models adjusted for potential patient-specific confounders.