 the final model was assessed by inspecting residual plots. All statistical analyses were performed with SAS software (version 9.1; SAS Institute Inc, Cary, North Carolina).
The study protocol was approved by the hospital's institutional review board. Only patients' oral informed consent for the anonymous treatment of their data was required since the study protocol was the same as that used for the standard medical care of these patients in our institution.
We prospectively studied 301 consecutive patients from January 2006 to December 2009. Their ages ranged from 18 to 82 years (mean [SD], 51  years),12 71.1% were male, and 28.9% were female, the mean (SD) BMI was 29.8 (4.6), the cervical perimeter was 40.6 (3.7) cm, and the FL150 was 0.80 (0.26) cm3/s.
The distribution of FTP, TS, and uvula scores, along with other patients' characteristics, are displayed in Table 1. Note that for these 3 scores, the 2 middle categories accounted for about 80% of the sample. The AHI values ranged from 0.7/hour to 89.5/hour (mean [SD], 27.6/hour [19.4/hour]). Ninety-four percent had an AHI value higher than 5.0/hour.
The AHI values showed a statistically significant correlation with FTP scores, TS scores, uvula scores, BMI, cervical perimeter, and age. In all cases, the correlation was positive, but its intensity varied markedly: while a high correlation was found in the case of the FTP score (Spearman r = 0.88) (Table 2), the correlation was only moderate for the cervical perimeter (r = 0.40) and very low for the TS scores, uvula scores, and age (Table 2). We did not detect a significant correlation between AHI values and the FL150.
The AHI values were significantly higher in males than in females (Wilcoxon rank sum test; P = .02): the median AHI value was 24.3/hour for males and 18.0/hour for females.
Almost three-quarters of patients (74.1%) had FTP scores of 2 and 3 (Table 1). Findings from 18 of 301 patient studies (6%) were considered normal (AHI <5.0/hour): 16 were classified as FTP 1, and only 2 as FTP 2.
All patients with an FTP score of 1 had an AHI value lower than 16.0/hour; in most of them (64.0%), the AHI value was 5.0/hour to 10.0/hour. Most patients with an FTP score of 2 (58.7%) had an AHI value of 10.0/hour to 20.0/hour. Two patients had normal values, and only 5 had an AHI value of 30.0/hour (all of them with a uvula index of 3). The FTP scores and AHI categories are shown in Table 3.
One patient with an FTP score of 3 had an AHI value of 13.4/hour, but all the others had an AHI value of 16.0/hour. The AHI value in most patients with an FTP score of 3 ranged from 32 to 48, with 3 patients showing an AHI value higher than 60.0/hour. All patients with an FTP score of 4 had an AHI value higher than 30.0/hour, corresponding to severe OSAS. The relation between FTP score and AHI is plotted in Figure 3.
Just over three-quarters of patients (77.4%) had TS scores of 1 and 2 and only 15 had a TS score of 3 (5.0%). None had a TS score of 4. Tonsil size scores of 3 and 4 are common in the pediatric population but are rare in adult OSAS. Fifty-two of the 301 patients (17.3%) had previously undergone tonsillectomy (Table 1). Figure 4 shows the progression of OSAS severity related to TS.
All patients with TS scores of 2 and 3 had an AHI value higher than 15.0/hr; AHI values were higher in the group with a TS score of 3. Curiously, AHI values in patients who had undergone tonsillectomy were higher than in those with a TS score of 1 and quite similar to those with a TS score of 2. Most of these patients were classified as having moderate to severe OSAS. Fifty-two (67%) had an AHI value higher than 15.0/hour, and only 4 (7.6%) had an AHI value lower than 5.0/hour. Uvula scores of 2 and 3 were found in 90.7% of the population (Table 1).
Table 4 shows the correlation of the AHI with the explanatory variables. The model with the lowest Cp value included the FTP score, FL150, the cervical perimeter, age, and the TS score (Table 4). Despite the high correlation coefficient, the TS score did not enter into the model when using the stepwise