Calculation of Cut-off Values Based on the Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) and Pemphigus Disease Area Index (PDAI) Pemphigus Scoring Systems for Defining Moderate, Significant and Extensive Types of Pemphigus

C. Boulard; S. Duvert Lehembre; C. Picard-Dahan; J.S. Kern; G. Zambruno; C. Feliciani; B. Marinovic; P. Vabres; L. Borradori; C. Prost-Squarcioni; B. Labeille; M.A. Richard; S. Ingen-Housz-Oro; E. Houivet; V.P. Werth; D.F. Murrell; M. Hertl; J. Benichou; P. Joly

Disclosures

The British Journal of Dermatology. 2016;175(1):142-149. 

In This Article

Results

Patient Characteristics

In total, 96 patients (59 female and 37 male) were enrolled in the study. Nineteen patients had PF and 77 had PV (22 with exclusive mucosal involvement, six with exclusive cutaneous involvement and 49 with both mucosal and cutaneous lesions). The median age was 50·5 years (range 19–84). The median duration of disease before diagnosis was 4·4 months (range 0·3–107·5).

The disease activity scores of the whole population were distributed over the first 34% (3–84 points) and 44% (0·5–90·5 points) of the PDAI and ABSIS scales, respectively (Figs 1, 2). The median PDAI activity and ABSIS scores of the whole population were 27·5 out of 250 points (range 3–84) and 34·8 out of 206 points (range 0·5–90·5), respectively. The median PGA score was 6 out of 10 points (range 1–10) and the median DLQI score was 9 out of 30 points (range 0–30). The median PDAI activity, ABSIS, PGA and DLQI scores of the PV and PF subpopulations are shown in Table 1.

Figure 1.

Distribution of Pemphigus Disease Area Index (PDAI) total activity and Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) total scores. The thick lines correspond to the median PDAI and ABSIS values of the whole population. The thin lines correspond to the 25th and 75th percentiles.

Figure 2.

Distribution of (a) Pemphigus Disease Area Index (PDAI), (b) Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) and (c) Physician's Global Assessment (PGA) scores for each patient in the three extent subgroups with mean (thick bar) and standard variation (thin bar).

Spearman's coefficient correlation was r = 0·52 (P < 0·001) between PDAI and ABSIS scores, r = 0·69 (P < 0·001) between PDAI and PGA scores and r = 0·56 (P < 0·001) between ABSIS and PGA scores.

Calculation of Cut-off Values Defining the Three Subgroups of Pemphigus Activity

The cut-off values (first and third quartiles) for the PDAI and ABSIS scores were 15 and 45 for the PDAI score, and 17 and 53 for the ABSIS score.

The respective median (range) PDAI activity scores in the three subgroups (moderate, significant and extensive) defined by the two cut-off values from the PDAI scoring system were 10·0 (3·0–14·0), 26·5 (15·0–44·0) and 61·0 (45·0–84·0) (P < 0·001). The respective median (range) ABSIS scores in the three subgroups defined by the two cut-off values from the ABSIS scoring system were 6·0 (0·5–15·3), 34·8 (17·0–52·8) and 56·0 (53·0–90·5) (P < 0·001) (Table 2).

Validation of the Three Pemphigus Activity Subgroups

To validate the classification in the three activity subgroups and to determine whether they were interchangeable, we compared the median ABSIS scores of the three subgroups defined by the two cut-off values from the PDAI scoring system, and vice versa. The respective median (range) ABSIS scores of the three subgroups (moderate, significant and extensive) defined by the 15- and 45-point cut-offs from the PDAI scoring system were 19·5 (0·5–39·5), 35·8 (1·5–90·5) and 52·8 (12·0–83·5) (P < 0·001). Conversely, the respective median (range) PDAI activity scores of the three severity subgroups defined by the 17- and 53-point cut-offs from the ABSIS scoring system were 16 (3–45), 25 (5–80) and 45 (23–84) (P < 0·001) (Table 2).

In order to identify among patients with moderate pemphigus a subgroup of patients with very few lesions who might be treated without corticosteroids, we calculated the cut-off values corresponding to the 10th percentile of the population. These cut-off values defining a fourth subgroup of patients with 'limited extent' were 10 and 4 points on the PDAI and ABSIS scores, respectively. However, the median PDAI and ABSIS scores of this fourth subgroup of patients with 'limited extent' were not statistically different from those of patients with 'moderate extent' (corresponding to patients from the 10th to the 25th percentile), which did not strongly argue for the definition of a fourth subgroup of patients.

To validate further the classification in the three disease activity subgroups defined by the cut-off values of the PDAI or ABSIS scoring systems, we calculated the median PGA and DLQI scores of these three subgroups for both scoring systems.

The median (range) PGA scores of the moderate, significant and extensive subgroups defined by the 15- and 45-point cut-off values of the PDAI score were 4 (1–6), 6 (2–9) and 8 (5–10), respectively (P < 0·001). When using the 17- and 53-point cut-off values of the ABSIS score, the median PGA scores of the moderate, significant and extensive subgroups were similar to the corresponding previous values: 4 (1–8), 6 (3–9) and 8 (5–10), respectively (P < 0·001) (Table 2).

The median (range) DLQI scores of the moderate, significant and extensive subgroups defined by the 15- and 45-point cut-off values of the PDAI score were 6 (0–30), 10 (0–30) and 12 (0–24), respectively (P = 0·02). When using the 17- and 53-point cut-off values of the ABSIS score, the median (range) DLQI scores of the moderate, significant and extensive subgroups were 6·5 (0–22), 10 (0–30) and 13 (0–30), respectively (P < 0·03) (Table 2).

Next we determined the proportions of patients with PF and patients with PV (overall, and according to clinical form: exclusive cutaneous involvement, exclusive mucosal involvement, both cutaneous and mucosal involvement) among the moderate, significant and extensive subgroups. The results are shown in Table 3.

Finally, we calculated cut-off values defining moderate, significant and extensive pemphigus according to the three clinical presentations of pemphigus: exclusive cutaneous involvement, exclusive mucosal involvement or both. The cut-off values differentiating the moderate from significant, and significant from extensive subgroups on the PDAI scale were rather close, irrespective of the exclusive cutaneous or exclusive mucosal presentation of patients (12 points vs. 11·5 points and 37 points vs. 35 points, respectively). These cut-offs were higher in patients with both skin and mucosal lesions (19 and 54 points, respectively). Conversely, these cut-off values on the ABSIS scale were close in patients with exclusive mucosal involvement or both mucosal and skin involvement, whereas they were much lower in the subgroup of patients with exclusive skin presentation (Table 4).

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