Results
A total of 371 participants were enrolled in the study from five sites,
with a preponderance of men (59%) and an average age of 51 years (SD
18) (Table 1). From these, 153 participants had sinus CT images
available.
Step 1
The endoscopic assessment presented an average ND of 9.8 cm (SD 0.9) and
CT distance of 8.4 cm (SD 0.9) for the total sample. In turn, the
external facial distances assessed in this study showed an average
curved distance of 11.8 cm (SD 0.9) and a perpendicular distance of 9.6
cm (SD 1). All four variables were significantly higher for men (Table
2).
Considering the endoscopic ND assessment as a reference, Δ Perpendicular
averaged -0.1 cm (SD 0.65, 95% CI -0.2 to -0.06), representing an
underestimation of true ND.
Conversely, Δ Curved averaged 2.0
cm (SD 0.83, 95% CI 1.9 to 2.1), representing an overestimation. In
turn, Δ CT scan averaged -1.2 cm (SD 0.8, 95% CI -1.3 to -1.07). The
overarching estimations held true on subgroup analysis for men and women
and therefore, inferences of ND error estimation for each of these three
variables persist regardless of
participant sex (Table 2).
The perpendicular distance was the most strongly correlated with ND
(P<0.001, R=0.775). Nonetheless, curved and CT distances also
showed a significant correlation to the endoscopic ND
(P<0.001, R=0.598, and P=0.001, R=0.541, respectively).
Self-reported ethnicity or age did not exert statistical significance on
any variable assessed on sub-group ANOVA (men and women).
Step 2
The stepwise multiple regression analysis to predict ND based on the
external facial distances controlled for age and sex and resulted in
three regression models and showed that 64% of the variance in ND can
be accounted for by the perpendicular distance alone (F(1,269) = 493.31,
p<0,0001) – model 1. Similarly, perpendicular and curved
distances were listed on model 2, being responsible for 66% of the
variance in ND (F(2,268) = 263.65, p<0,0001). On model 3, sex
and both facial distances were included, accounting for 66% of ND
variance (F(3,267)= 179.98, p<0,0001). Age was removed as a
variable in all regression models.
The three models were then tested against the data of the remaining 100
participants, as ND = Perpendicular distance*0.773 + 2.344 (model 1), ND
= Perpendicular distance*0.672 + Curved distance*0.171 + 1.28 (model 2),
and ND = Perpendicular distance*0.662 + Curved distance*0.147 + Sex*1.7
+ 1.56 (model 3). The ND prediction error using model 1 was 0.03 cm (SD
0.61; 95% CI -0.08 to 0.16), while model 2 presented an average
overestimation of 0.03 cm (SD 0.58; 95% CI - 0.78 to 0.15). In turn,
model 3 resulted in a mean of 0.9 cm (SD 1; 95%CI 0.7 to 1.1).