A study examining inter-rater and intrarater reliability of a novel instrument for assessment of psoriasis: the Copenhagen Psoriasis Severity Index

Background There is a perceived need for a better method for clinical assessment of the severity of psoriasis vulgaris. The most frequently used system is the Psoriasis Area and Severity Index (PASI), which has significant disadvantages, including the requirement for assessment of the percentage of skin affected, an inability to separate milder cases, and a lack of linearity. The Copenhagen Psoriasis Severity Index (CoPSI) is a novel approach which comprises assessment of three signs: erythema, plaque thickness and scaling, each on a four‐point scale (0, none; 1, mild; 2, moderate; 3, severe), at each of 10 sites: face, scalp, upper limbs (excluding hands and wrists), hands and wrists, chest and abdomen, back, buttocks and sacral area, genitalia, lower limbs (excluding feet and ankles), feet and ankles. Objectives To evaluate the inter‐rater and intrarater reliability of the CoPSI and to provide comparative data from the PASI and a Physician’s Global Assessment (PGA) used in recent clinical trials on psoriasis vulgaris. Methods On the day before the study, 14 dermatologists (raters) with an interest in psoriasis participated in a detailed training session and discussion (2·5 h) on use of the scales. On the study day, each rater evaluated 16 adults with chronic plaque psoriasis in the morning and again in the afternoon. Raters were randomly assigned to assess subjects using the scales in a specific sequence, either PGA, CoPSI, PASI or PGA, PASI, CoPSI. Each rater used one sequence in the morning and the other in the afternoon. The primary endpoint was the inter‐rater and intrarater reliability as determined by intraclass correlation coefficients (ICCs). Results All three scales demonstrated ‘substantial’ (a priori defined as ICC > 80%) intrarater reliability. The inter‐rater reliability for each of the CoPSI and PASI was also ‘substantial’ and for the PGA was ‘moderate’ (ICC 61%). The CoPSI was better at distinguishing between milder cases. Conclusions The CoPSI and the PASI both provided reproducible psoriasis severity assessments. In terms of both intrarater and inter‐rater reliability values, the CoPSI and the PASI are superior to the PGA. The CoPSI may overcome several of the problems associated with the PASI. In particular, the CoPSI avoids the need to estimate a percentage of skin involved, is able to separate milder cases where the PASI lacks sensitivity, and is also more linear and simpler. The CoPSI also incorporates more meaningful weighting of different anatomical areas.     

A study examining inter- and intrarater reliability of three scales for measuring severity of psoriasis: Psoriasis Area and Severity Index, Physician's Global Assessment and Lattice System Physician's Global Assessment

BACKGROUND: There is a lack of consensus as to the best way of monitoring psoriasis severity in clinical trials. The Psoriasis Area and Severity Index (PASI) is the most frequently used system and the Physician's Global Assessment (PGA) is also often used. However, both instruments have some drawbacks and neither has been fully evaluated in terms of 'validity' and 'reliability' as a psoriasis rating scale. The Lattice System Physician's Global Assessment (LS-PGA) scale has recently been developed to address some disadvantages of the PASI and PGA. OBJECTIVES: To evaluate the inter-rater and intrarater reliability of the PASI, PGA and LS-PGA. METHODS: On the day before the study, 14 dermatologists (raters), with varied experience of assessing psoriasis, received detailed training (2.5 h) on use of the scales. On the study day, each rater evaluated 16 adults with chronic plaque psoriasis in the morning and again in the afternoon. Raters were randomly assigned to assess subjects using the scales in a specific sequence, either PGA, LS-PGA, PASI or PGA, PASI, LS-PGA. Each rater used one sequence in the morning and the other in the afternoon. The primary endpoint was the inter-rater and intrarater reliability as determined by intraclass correlation coefficients (ICCs). RESULTS: All three scales demonstrated 'substantial' (a priori defined as ICC > 80%) intrarater reliability. The inter-rater reliability for each of the PASI and LS-PGA was also 'substantial' and for the PGA was 'moderate' (ICC 75%). CONCLUSIONS: Each one of the three scales provided reproducible psoriasis severity assessments. In terms of both intrarater and inter-rater reliability values, the three scales can be ranked from highest to lowest as follows: PASI, LS-PGA and PGA.     

A cross‐sectional study using the Children’s Dermatology Life Quality Index (CDLQI) in childhood psoriasis: negative effect on quality of life and moderate correlation of CDLQI with severity scores

Background Juvenile psoriasis is a chronic and incurable skin disease that affects approximately 0·7% of children. Objectives To achieve more insight into the quality of life (QoL) in childhood psoriasis and to investigate whether disease severity scores correlate with QoL scores. Methods All consecutive patients with juvenile plaque psoriasis (≤ 18 years old) who visited our outpatient department were included. At baseline, the Children’s Dermatology Life Quality Index (CDLQI) questionnaire was completed and disease severity was assessed by the Psoriasis Area and Severity Index (PASI) and the Physician Global Assessment (PGA). Results Thirty‐nine patients were included in the study. A median CDLQI of 6 [interquartile range (IQR) 5–9] was reported. Median PASI was 6·3 (IQR 3·3–8·2) and median PGA was 2 (IQR 1–3). The correlation coefficient between PASI and CDLQI was 0·47 (P = 0·003), whereas the correlation coefficient between PGA and CDLQI was 0·51 (P = 0·001). Conclusions The negative effect on QoL in juvenile psoriasis was confirmed in the largest cohort presented up to now. The correlation between disease severity scores and disease‐related QoL in children with psoriasis is only moderate. Therefore, both clinical outcome parameters (PASI, PGA) and measures of QoL (CDLQI) should be included in adequate, patient‐oriented clinical decision making.