## 3 Results  
Twenty-one patients were included in this study, and two patients in the PI group were discarded due to sample contamination. Figure 4 shows the distribution of the patients (Figure 5). The mean age of the patients was 58.52 years (confidence interval (CI) = 54.05-62.99); the mean age of male patients was 58.71 years (CI = 49.92-67.50); and that of female patients was 58.42 years (CI = 52.45-64.39). The PI group comprised 11 patients from the Murcia region. The mean age of the patients was 58.45 years (CI = 53.63-63.27); 7 were females, and 5 were males. The mean age of the males was 60.75 years (CI = 46.37-75.12), and for the females it was 57.14 years (CI 51.33-62.95). Finally, the HI group comprised 10 patients (3 males and 7 females) with a mean age of 58.60 years. The mean age of the males was 56.00 years (CI = 27.78-84.21), and the mean age of the females was 59.71 years (CI = 47.02-72.40) (Figure 6). Figure 4: Negative test results. The clinical characteristics of the control group and peri-implant group are reported in Tables 1 and 2. As would be expected, plaque and bleeding scores were clearly higher in the IP group than in the control group (Figures 7 and 8). Figure 5: Test results and presence of PI. Figure 6: Box plot showing the age of the patients who agreed to participate in the study. There were no statistically significant differences. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Age** & **Sex** & **Probing Depth** & **Plaque Index** & **Gingival Index** \\ \hline
62 & H & 5 mm & 3 & 3 \\
73 & H & 5 mm & 3 & 3 \\
55 & H & 5 mm & 3 & 3 \\
61 & M & 4 mm & 2 & 2 \\
63 & M & 5 mm & 2 & 2 \\
55 & M & 6 mm & 3 & 3 \\
51 & M & 8 mm & 2 & 2 \\
60 & M & 9 mm & 3 & 3 \\
53 & H & 5 mm & 2 & 2 \\
47 & M & 6 mm & 2 & 2 \\
63 & M & 8 mm & 3 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Clinical characteristics of the PI group. Figure 7: Box plot showing plaque indices in healthy and peri-implantitis populations. There were statistically significant differences, with the PI group presenting a greater accumulation of plaque. The mean probing depth was significantly deeper in the PI group than in the HI group (\(p<0.001\)). To determine the diagnostic value of this test, sensitivity and specificity were assessed, as they are traditional parameters that demonstrate the validity of qualitative tests. The validity test results indicated greater specificity than sensitivity; that is, the test better identifies patients who have the disease. Sensitivity (S) was calculated as the quotient of the number of true positives (patients who have peri-implantitis and the test has been positive) among the total number of patients with PI. The probability that the test identified a patient with PI was 0.09. Specificity (E) was calculated as the quotient of the true negatives (patients without PI and a negative test) among the total number of patients in the HI group, with a maximum value of one. Specificity was used to determine the probability that the test results are negative for those who do not have PI. Prevalence was considered the proportion of patients with PI; in this study, the prevalence was 0.52. All results are summarized in Table 3.  
Figure 8: Box plot showing gingival indices for healthy and peri-implantitis patients. The level of bleeding was significantly higher in the PI group than in the HI group. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value** & **\%** \\ \hline Sensitivity & 0.09 & 9.1\% \\ Specificity & 1 & 100\% \\ Prevalence & 0.52 & 52\% \\ Positive Post-test & 1 & 100\% \\ Negative Post-test & 0.5 & 50\% \\ Positive LR+ & Infinity & \\ Negative LR & 0.91 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of the test results. To construct the Fagan nomogram [18], probability ratios (likelihood ratio) were calculated and plotted on graphs. A Fagan nomogram is a tool used to interpret the results of a medical or diagnostic test and evaluate the probability that a person has a disease or health condition (Figure 9).