Can you produce the risk of bias according to the Agency for Healthcare Research and Quality for the study “Comparison of gingival crevicular fluid and serum human beta- defensin-2 levels between periodontal health and disease” while i provide you with the following data from the study:                                                                                                                                                                                                                                             1. Participant selection and clinical evaluations
"In this cross-sectional study, 42 CP patients and 59 controls were recruited from either patients attending to the Department of Periodontology, Faculty of Dentistry, or from the personal patient populations of the academic faculty and postgraduate students at the Ondokuz Mayis University between June 2014 and May 2015. Ethics committee approval was received from Ondokuz Mayıs University clinical research ethics committee with decision number 2014/556-630(2013/416-447).
Individuals included in the study were informed about the purpose and content of the study and signed an informed consent form indicating they voluntarily participated in the study.",
2. Inclusion criteria
"Individuals included were over 18 years old and willing to provide in- formed consent. In addition, they did not have any systemic diseases including cardiovascular diseases, diabetes, chronic renal failure, and hepatitis B and C, and were not using any chronic anti-inflammatory drugs. Moreover, participants who are pregnant or lactating at the time of the study or receive any periodontal treatment within the preceding six months were excluded from the study. All subjects were evaluated clinically and radiographically at the first clinical visit; periapical and panoramic radiographs were obtained from all patients to verify the clinical periodontal diagnosis and the extent of alveolar bone loss. All clinical parameters were evaluated by a single investigator (S.K). The examiner was calibrated against an expert periodontist. Calibration was validated if 90% of the recordings could be reproduced within a 1.0-mm difference (Badersten, Nilvéaus, & Egelberg, 1984). The following clinical parameters were assessed at six sites per tooth: probing pocket depth (PD); clinical attachment loss (CAL); bleeding on probing (BOP) (Ainamo & Bay, 1975); plaque index (PI) (Silness & Löe, 1964); gingi- val index (GI) (Löe & Silness, 1963); and the number of missing teeth, mobility, and furcation involvement. PD was defined as the distance between the coronal-most margin of the free gingiva to the most apical penetration of the Michigan-0 probe. CAL was defined as the distance from the cemento-enamel junction to the most apical penetration of the Michigan-O probe. The presence of supragingival plaque was recorded dichotomously during PD measurements. Bleeding on probing (BOP) within 20s was recorded dichotomously.Clinical and radiographic criteria proposed by the 1999 International World Workshop were used for diagnosis.",
3. Control group
"Patients had no history of periodontitis, and no furcation involvement and mobility. Their PD was smaller than 3 mm.", 
4. CP group inclusion criteria
"Radiographic evidence of alveolar bone loss and at least ≥4 mm PDD in two interdental areas, not on the same tooth (Eke, Page, Wei, Thornton-Evans, & Genco, 2012).",
5. Collection and storage of samples
"GCF samples were obtained for analyses (mainly from the maxillary premolar area for standardization). The supragingival plaque was removed without touching the gingival margin. The area was care- fully washed with water to prevent salivary contamination, the tooth was isolated with cotton rolls, and the area was dried with air for 10 s. For sampling, paper strips (Periopaper, ProFlow, Amityville, NY,USA) were carefully placed in the gingival sulcus and held there for 30 s. If the paper strips were contaminated with blood or saliva, they were discarded and replaced. The volume of each paper strip was determined with Periotron 8,000 (ProFlow, Amityville, NY, USA). The samples were placed with 50 microliters of phosphate-buffered saline (pH 7.0) in an Eppendorf tube. Two milliliters of peripheral venous blood samples were taken from each subject, using a standard venipuncture method. The sam- ples were then transferred to tubes containing 8% liquid EDTA. GCF samples were centrifuged at 1,000 × g for 10 min; blood samples were centrifuged at 3,000 × g for 10 min by a centrifuge device (Shimadzu UV160A, SNo: 28006648, Japan). The supernatants obtained from GCF and serum samples were separated for the study. The samples were mixed thoroughly with a vortex and stored at −80oC until the working day. On the working day, the samples were brought to room temperature." .