A Priori Estimation of the Narrow-Band UVB Phototherapy Outcome for Moderate-to-Severe Psoriasis Based on the Patients’ Questionnaire and Blood Tests Using Random Forest Classifier

Figures & data

Table 1 Statistical Characteristics of the Phototherapy After the First and Second Courses of NB-UVB Phototherapy for Various Groups of Patients

Course/Patient Group	ΔPASI	ΔBSA	ΔPGA	n
Statistics
After first/all patients	63±20	51±21	47±20	71
	66 (8, 94)	50 (3, 83)	50 (0, 80)
After first/present in first and absent in second	65±20	54±20	49±22	50
	66 (19, 94)	53 (5, 83)	50 (0, 80)
After first/present in first and present in second	60±21	45±20	42±17	21
	63 (8, 89)	45 (3, 82)	50 (0, 67)
After second/present in first and present in second	56±23	43±22	40±22	21
	57 (8, 91)	48 (0, 78)	50 (0, 75)
Probability
After first/present in second vs absent in second	0.42	0.12	0.11	21/50
After second/present in first vs present in second	0.54	0.87	0.33	21/21

Notes: The mean value and ±SD for the relative changes of the psoriatic metrics for each round of the phototherapy. The corresponding values of the median and the min-max range (in parentheses). n, number of patients in each group. Probability of the similar statistical distribution of outcomes. ΔNormalized difference (end value minus start value as a percentage of the starting value).

Abbreviations: BSA, body surface area; PASI, Psoriasis Area and Severity Index; PGA, Physician Global Assessment.

Figure 1 Box and whisker plot for the relative change in psoriatic severity measure (as a percentage of the value at the start of phototherapy), after the first and second rounds of 20 narrowband UVB exposures.

Abbreviations: BSA, body surface area; PASI, Psoriasis Area and Severity Index; PGA, Physician Global Assessment.

Table 2 Statistical Characteristics of the RF Classification, without Cytokine Input, for Various Sub-Groups of the Psoriatic Patients

Statistic	“Positive”: ΔPASI ≥50 “Negative”: ΔPASI <50	“Positive”: Remission ≤8 months “Negative”: Remission >8 months	“Positive”: Out of second Course “Negative”: in second Course
	Value (95%CI)	Value (95%CI)	Value (95%CI)
Sensitivity	83.7 (70.3–92.7)	94.1 (71.3–99.9)	86.3 (72.7–94.8)
Specificity	54.6 (32.2–75.6)	70.0 (34.8–93.3)	66.7 (46.0–83.5)
Positive likelihood ratio	1.84 (1.15–2.96)	3.14 (1.21–8.15)	2.59 (1.50–4.47)
Negative likelihood ratio	0.30 (0.14–0.63)	0.08 (0.01–0.59)	0.20 (0.09–0.45)
Positive predictive value	80.4 (71.9–86.8)	84.2 (67.3–93.3)	80.9 (71.0–87.9)
Negative predictive value	60.0 (41.7–75.9)	87.5 (50.1–98.0)	75.0 (57.7–86.9)
Accuracy	74.7 (62.9–84.2)	85.2 (66.3–95.8)	78.9 (67.6–87.7)
Accuracy^a	71.8 (59.9–81.9)	85.2 (66.3–95.8)	76.1 (64.5–85.4)

Note: ^aAccuracy of the classification with cytokine input, ΔNormalized difference (end value minus start value as a percentage of the starting value).

Abbreviation: PASI, Psoriasis Area and Severity Index.

Table 3 Ranking of Explanatory Variables from Most Important to Least Important

Output	Explanatory Variables
ΔPASI	Psoriasis in ancestors, number of previous cycles of exposures, LDL, glucose level, the education degree, use of emollients, psoriatic arthritis, difference between the year of the first psoriasis phototherapy and the year of psoriasis diagnosis, taking antidepressants, total cholesterol
Duration of remission	Material status, difference between the year of the first psoriasis phototherapy and the year of psoriasis diagnosis, number of earlier phototherapy treatments, psoriatic arthritis, taking diabetic drugs, glucose level, years of smoking, psoriatic arthritis, frequency of psoriasis exacerbations per year
Phototherapy continuation	BSA at the start of the first round, PGA at the start, number of cigarettes smoked per day, PASI at start, years of life, psoriasis in ancestors

Note: ΔNormalized difference (end value minus start value as a percentage of the starting value).

Abbreviations: BSA, body surface area; LDL, low-density lipoprotein; PASI, Psoriasis Area and Severity Index; PGA, Physician Global Assessment.