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30 minutes in order to stabilize temperature (20
ġ
±2
ġ
C) and humidity (50-70%). Other outcomes
included severity of psoriasis and quality of life as measured by EQ-5D-5L questionnaire. Severity of
psoriasis was evaluated by a dermatologist at baseline and at the end of the 4
th
week, using PASI score
which assesses the severity and extent of psoriasis lesions and the area affected. PASI score varies from
0 to 72 with higher scores indicating more severe conditions [21]. Quality of life was measured using
EQ-5D-5L questionnaire (Thai versions), which was evaluated by Juntana Pattanaphesaj in 2014 to
assess general health status. The respondent was asked to indicate the health state by checking in the
box corresponding to the most appropriate statement in each of the 5 dimensions [22]. EQ-5D-5L was
evaluated at baseline and at the end of the 4
th
week.
Statistical analysis
Statistical analyses were performed with SPSS 18 for Windows software. Means, standard
deviations (SD), median and inter-quartile range (IQR) were used to summarize the data in this study.
Effects of liquid paraffin and cream base on TEWL and skin hydration in normal skin and psoriasis
lesions were compared within the same subject using Wilcoxon signed-rank test. Comparisons of PASI
score and EQ-5D-5L between baseline and at the end of the 4
th
week were also carried out using
Wilcoxon signed-rank test. All p-values are two-sided, with the p value less than 0.05 being considered
statistically significant.
Results and discussion
One hundred participants with plaque psoriasis were enrolled. There were 48 females and
52 males, aged 18 to 74 (mean age 45±13) years. Average duration of psoriasis was 12 years and most
patients had Fitzpatrick skin type IV (95%). Body areas affected include forearms (42%), legs (27%), back
(16%) and thighs (5%).
Table 1 shows the effect of LP and CB on TEWL in normal skin and psoriasis lesions. For
normal skin, TEWL at the end of 4-week treatment period decreased in areas applied with LP (median
change from baseline -0.30 g/m
2
/h), but increased in areas applied with CB (median change from
baseline 0.30 g/m
2
/h) (p=0.011 for comparison between LP and CB). For psoriasis lesions, TEWL also
decreased with LP (median change from baseline -1.00 g/m
2
/h), but remained quite stable with CB
(median change from baseline 0.05 g/m
2
/h). However, this difference was not statistically significant.
The effect of LP and CB on skin hydration in normal skin and psoriasis lesions is shown in table
2. For normal skin, both treatments increased skin hydration after 4 weeks of treatment (5.04 AU for LP
and 4.20 AU for CB), but there was no statistically significant difference between LP and CB. For
psoriasis lesions, application with CB increased skin hydration to a statistically significantly greater
extent than with LP (4.00 AU for CB vs. 2.65 AU for LP, p=0.006 for comparison between CB and LP).
In Figure 1, TEWL and skin hydration at 4 weeks compared with baseline on normal skin and
psoriasis lesions treated with either LP or CB. TEWL on both studied areas showed not significant.
While, both studied areas showed significant increase of skin hydration (p<0.0001), see figure 2.
