The internal consistency was acceptable for the observer components of the POSAS, with Cronbach's alpha values of 0.889, and 0.770 respectively.
The interobserver reliability (Table 1) was "almost perfect" for the OST Group and "substantial" for the PDT group of the observer component of the POSAS in terms of total score (the average measures of ICC were, 0.876 and 0.728, respectively). For the individual observer component of the POSAS in the OST group, interobserver reliability was "almost perfect" for vascularity, relief and surface area (0.913, 0.913, 0.947 respectively) and “substantial” for pigmentation, thickness and pliability (0.768, 0.802, and 0.627, respectively). In the group with PDT, interobserver reliability was “substantial” for pigmentation, thickness, relief, pliability and surface area (0.647, 0.672, 0.779 0.693 and 0.713 respectively), and “moderate” for vascularity (0.440).
Table 1
Interobserver reliability of the observer component of the patient and observer scar assessment scale
Observer component of the POSAS
|
Single measure ICC (95% CI), OST group
|
Average measure ICC (95% CI), OST group
|
Single measure ICC (95% CI), PDT group
|
Average measure ICC (95% CI), PDT group
|
Vascularity
|
0.777 (0.689~0.845)
|
0.913(0.849~0.943)
|
0.207(0.078~0.350)
|
0.440(0.201~0.618)
|
Pigmentation
|
0.525 (0.395~0.646)
|
0.76 (0.662~0.846)
|
0.380(0.230~0.525)
|
0.647(0.473~0.768)
|
Thickness
|
0.575 (0.431~0.696)
|
0.80 (0.694~0.873)
|
0.405(0.253~0.550)
|
0.672(0.503~0.786)
|
Relief
|
0.777(0.681~0.849)
|
0.91 (0.865~0.944)
|
0.541 0.394~0.668)
|
0.779(0.661~0.858)
|
Pliability
|
0.359(0.219~0.501)
|
0.62 (0.456~0.751)
|
0.429(0.275~0.573)
|
0.693(0.532~0.801)
|
Surface area
|
0.856 (0.781~0.906)
|
0.947(0.914~0.967)
|
0.453(0.311~0.588)
|
0.713(0.575~0.811)
|
Total
|
0.702(0.585~0.793)
|
0.876(0.809~0.920)
|
0.472(0.303~0.618)
|
0.728(0.566~0.829)
|
CI: confidence interval, single measure ICC: intraclass correlation coeficient for a single observer, average measure ICC: intraclass correlation coefficient for the group of three observers. |
The total observer scale parameter values vary from 6 (min) to 35 (max) in the OST group and from 6 (min) to 22 (max) in the PDT group. As shown in Table 3, the mean total values of the POSAS observer scale as well the separate parameters (except vascularity) are not statistically different in both groups. The mean total score using the observer component of POSAS for OST post-tracheostomic scars was 12.00 ±0.370, and that for the PDT group was 12.08 ±0.280 (p=0.86) (Table 2).
Table 2
POSAS observer scale parameters mean values
Observer Scale parameters
|
POSAS Observer Scale Value, OST group
|
POSAS Observer Scale Values, PDT group
|
P value
|
|
|
|
|
Vascularity
|
1.79 ± 0.053
|
1.42 ± 0.037
|
0.000
|
Pigmentation
|
1.79 ± 0.007
|
1.87 ± 0.051
|
0.40
|
Thickness
|
1.94 ± 0.075
|
1.97 ± 0.050
|
0.76
|
Relief
|
2.38 ± 0.093
|
2.45 ± 0.073
|
0.56
|
Pliability
|
1.79 ± 0.068
|
1.90 ± 0.055
|
0.20
|
Surface
|
2.30 ± 0.096
|
2.48 ± 0.081
|
0.16
|
Total score
|
12.00±0.370
|
12.08±0.280
|
0.86
|
Differing cosmetic results have shown the POSAS Observer Scale data for persons with different durations of tracheostomic tube cannulation time. The results showed that the patients who had a tracheostomic tube cannulation period of less than 15 days had better cosmetic results than those who had tracheostomic tubes for more than 15 days, regardless of the method of tracheostomy. Thus, 36 patients from the OST group were cannulated for less than 15 days, and the average Observer Scale total score was 6.64± 0.082 in comparison with 40 patients with more than 15 days of cannulation period and total value of 16.15± 0.096 (p<0.001). 23 patients from the PDT group had a tracheostomic tube cannulation duration of less than 15 days with average Observer Scale total score of 7.26± 0.211 in comparison with patients who underwent more than 15 days of cannulation period 14.17± 0.379 (p<0.05). Persons that were cannulated for more than 15 days had the worst results in both groups and showed values of 16.15± 1.130 and 14.17± 0.379, respectively, (Table 3).
Table 3
POSAS observer and patient scale values depending on duration of tracheostomic tube cannulation
Parameters
|
Less than 15 days cannulation
|
More than 15 days cannulation
|
POSAS observer scale mean total value, OST group
|
6.64± 0.13
|
16.15± 1.13*
|
POSAS observer scale mean total value , PDT group
|
7.26± 0.21
|
14.17± 0.38
|
POSAS patient scale mean total value, OST group
|
6.76 ±0.23
|
13.12±0.44
|
POSAS patient scale mean total value, PDT group
|
7.08 ±0.19
|
12.50±0.69
|
P< 0.05, *P< 0.001 |
This could be the consequence of tracheostomic tube flanges extended pressure on tissues around the incision zone, which results in tissue atrophy and worst cosmetic results, especially in the Relief and Surface parameters of the POSAS Observer Scale (Figs. 1 and 2).
Patient POSAS component self-assessment tool
On simple linear regression analysis, the patients' overall opinion regarding their own scars was significantly influenced by scar-related itchiness, color, stiffness, thickness, and irregularity (p<0.005; Table 4).
Table 4
Simple linear regression analysis of variables associated with patient scar assessment scale scores
Items
|
Slope coefficient, OST
|
p-value, OST
|
Slope coefficient, PDT
|
p-value, PDT
|
|
|
|
|
|
Pain
|
0.65
|
0.000
|
0.65
|
0.000
|
Itchiness
|
0.66
|
0.000
|
0.75
|
0.000
|
Color
|
0.81
|
0.000
|
0.80
|
0.000
|
Stiffness
|
0.83
|
0.000
|
0.89
|
0.000
|
Thickness
|
0.88
|
0.000
|
0.91
|
0.000
|
Irregularity
|
0.81
|
0.000
|
0.89
|
0.000
|
As demonstrated in Table 5, the total scores of patients’ self-assessment parameters in both groups were also not statistically different. They amount of 9.51±0.441 in OST group and 9.49±0.392 in PDT Group. The minimal value of total scores for each group is 6 and the maximum is 60. Therefore, generally, the total score amount for both groups could be interpreted as close to normal skin imaginable scars.
Table 5
POSAS patient scale parameters values
Patient Scale Parameters
|
OST Group
|
PDT Group
|
P value
|
Pain
|
1.22±0.069
|
1.18±0.049
|
0.64
|
Itchiness
|
1.24±0.065
|
1.14±0.041
|
0.23
|
Color
|
1.58±0.088
|
1.54±0.091
|
0.74
|
Stiffness
|
1.74±0.098
|
1.75±0.082
|
0.99
|
Thickness
|
1.71±0.104
|
1.83±0.085
|
0.38
|
Irregularity
|
1.80±0.118
|
2.05± 0.117
|
0.13
|
Total score
|
9.51±0.441
|
9.49±0.392
|
0.96
|
|
|
|
|
However, when comparing the values of the total score of the patient assessment scale between persons who underwent tracheostomy intubation for less than 15 days duration with those who were cannulated for more than 15 days, the results were different as in the observer assessment scale: 6.76±0.232 for the OST group and 7.08 ±0.396 in persons with less than 15 days of cannulation period and 13.12 ±0.442 and 12.5±0.696, respectively, for longer than 15 days cannulated persons.
The Dermatology Life Quality index (DLQI) scores have shown a mean value of 0.6 ±0.013, which means that post-tracheostomic scarring in the presented study, had no effect on the patient's life.
Points 3, 5, 6, 7, 8, and 9 of the questionnaire had a value of 0 for all 156 persons. Point 10 (over the last week, how much of a problem has the treatment for your skin been, for example, by making your home messy, or by taking up time?) was not relevant for all participants involved. Point one (over the last week, how itchy, sore, painful, or stinging has your skin?) had a maximum value <<1>>, which is scored as a little impact at 39 persons. Points two and four of the questionnaire had a maximum value <<1>> in an 11 persons.