Disease Assessment in Psoriasis

Abstract

Researchers are making all out efforts worldwide, to find a serological marker to monitor the disease severity and/or measure efficacy of the drug. There are many potential molecular targets being investigated as a candidate marker. However, till date there has been no significant breakthrough. Thus, various scoring systems have been devised to evaluate the disease severity in psoriasis. In spite of constant revisions of the scores being currently used, from time to time. None of the scores yet satisfy all the validation criteria desired of an ideal scoring system. And this is partly also because of the fact that the psoriasis has such a huge range of clinical variants. Nevertheless, in the recent past, significant progress has been made in this direction.

Introduction

Psoriasis does not yet have any serological marker to assess the severity or monitor the efficacy of the drug. Although researchers from all over the world continue to engage, looking for that ever-elusive marker.

Fortunately, we as dermatologists are privileged to have naked-eye access to the whole of the skin and are thus better positioned to device certain clinical parameters to assess the severity of most dermatological diseases, including psoriasis. And, over the years, clinicians have used various scoring systems to evaluate the severity of psoriasis using both quantitative as well as qualitative measures, including percent body surface area (BSA), the Psoriasis Area and Severity Index (PASI) and the Dermatology Life Quality Index (DLQI). However, none of the currently used severity scores meets all the validation criteria required for an ideal score.

In psoriasis, the picture is further complicated by the fact that it has a large number of clinical variants, starting from guttate to pustular to localised nail or palmo-plantar disease. Furthermore, psoriasis is just not limited to skin with the joints and nails being directly involved, they too contribute independently to the severity of the disease. And, not to forget, the huge psychological impact that this disease can have, leading to severely impaired quality of life of the patient, needs to be factored in while assessing the severity of the disease. In this short review, we shall discuss in details our journey of scoring systems developed this far to assess the severity of psoriasis.

Psoriasis area and severity index (PASI)

It was first introduced in 1978 by Fredriksson and Petersson.[1] It is the highest validated score for quantitative evaluation of the clinical severity of psoriasis, and even after being into existence for nearly half a century, it still remains the gold standard single scoring scale for the assessment of extensive plaque psoriasis. In this scoring system, four sites, including the head (h), upper limb (u), trunk (t) and lower limbs (l), are separately scored on three parameters: erythema (E), induration (I) and scaling (D). And each one of these parameters is graded on a severity scale of 0–4 (where 0 stands for nil; 1 is mild; 2 is moderate; 3 is severe; and 4 is considered very severe). The area-wise percentage involvement of the involved sites is calculated as follows: 1 = less than 10% involvement; 2 = 10–29%; 3 = 30–49%; 4 = 50–69%; 5 = 70–89%; and 6 = more than 90%. The severity grading of the three symptoms is multiplied by the numerical value of the areas involved and by the various percentages of the four body areas. These values are then added to obtain the PASI. The final formula for PASI score is: PASI = 0.1 (Eh + Ih + Dh) Ah + 0.2 (Eu + Iu + Du) Au + 0.3 (Et + It + Dt) At + 0.4 (El + Il + Dl) Al. The maximum score of the PASI is 72. PASI 75 means a 75% reduction in baseline PASI score.

Digital PASI

Recently, various PASI-calculating apps have become available,[2] which are easy to use and save a lot of time by doing the calculations itself; the physician is just supposed to enter the data, and the resultant score is automatically calculated.

3-Dimensional Computerised PASI Scoring Tool (3D-PASI tool)

Also, a group of researchers led by UAF[3] in 2000 developed a new 3D-PASI tool. Although, in this scoring tool, the same parameters as conventional PASI Scoring are used. But it incorporates the use of graphics and 3D-computer technology to reduce the dependence on human judgement and thus minimise the interobserver variations.

Limitations

It does not take into consideration the severity of nail involvement and cannot be applied to other morphological variants of psoriasis like ‘generalised pustular psoriasis’ or localised variants like ‘palmo-plantar psoriasis’.

Salford Psoriasis Index (SPI)

Kirby et al.[4] in the year 2000 proposed “The Salford Psoriasis Index (SPI)” as a measure of assessing psoriasis. SPI was derived after combining the converted PASI score, psychosocial disability score and a third score based on historical information related to the severity of the disease. In this, basically, the first figure denotes the extent of psoriasis on a scale of 0–10 by converting the PASI score. The second figure denotes the psychosocial impact on a 0–10 visual analogue scale. Whereas the third figure indicates the historical severity of the disease by taking into account the treatment received in past, a number of episodes of erythroderma and/or hospital admissions.

Simplified psoriasis index (SPI)

Chularojanamontri et al.[5] later published a modified version of the SPI renamed to Simplified Psoriasis Index. In this, the derived PASI score is replaced with a composite weighted severity score designed to reflect the functional and psychosocial impairment caused by psoriasis.

Self-administered psoriasis area severity index[6]

The patient administered PASI score, which differs from the standard PASI by the fact that here the patient evaluates a representative lesion for all the parameters. Whereas in PASI, lesional severity is scored separately in each involved area.

Low PASI score

Otero et al.[7] in 2014 devised PASI score to affectively assess the severity of psoriasis involving small areas of the body. This was done essentially to overcome one of the major limitations of classical PASI, which was found to be insensitive in cases with lower scores (less than 10% BSA involvement). Low PASI has the same components as the classic PASI scale; only the ‘area score’ of classic PASI has been categorised in a four-point scale (Area 0.25 denotes 0.1–2.5% involvement; 0.5 means 2.6–5%; 0.75, 5.1–7.5%; 1, 7.6–9.9%).

PASI-high discrimination [Figure 1]

Figure 1.

PASI-high discrimination (PASI-HD) Score graphic representation

Very recently, Papp et al.[8] have proposed another scale to assess the severity of psoriasis affecting small areas (less than 10% BSA within any given anatomical region). Here again, in areas of involvement <10% on classic PASI, instead of mentioning area as 1 (in classic PASI), it is given in a linear score of 0.1–0.9 for 1–9% involvement (by hand print method).

Physician Global Assessment (PGA)

It is basically an average assessment of the disease severity by a physician based on the erythema, scale and induration of all the psoriatic plaques. It is a quick method and is very easy to perform, thus making it a suitable tool in everyday practice. The PGA score ranges from 0 to 5, wherein 0 signifies no lesion or clear, 1 = almost clear, 2 = mild, 3 = moderate, 4 = severe and 5 = very severe. It neither quantifies the BSA involved nor evaluates the individual lesion locations.^R There are two basic PGA scales: one is static (assesses severity at a given point in time), and the other is dynamic (assesses improvement from baseline).[9]

BSA

It is based on the “rule of nines”, which was originally developed to assess the area of involvement in a burn case.[10] In this, each of the following 11 body parts is awarded 9% of BSA (head and neck, 2X arms, 2X anterior and posterior legs, 4X trunk) and the remaining 1% is for genitalia. The other way to calculate the area involved is by calculating the number of patient's hand areas affected, where one hand print reflects 1% BSA.[11]

DLQI

Finlay et al.[12] in 1994 devised an easy-to-use, simple and practical patient-reported questionnaire-based scale to evaluate the impact of skin diseases on the quality of life of patients. It was introduced to evaluate the severity of psoriasis when it was found that it was equally important to address the psychosocial aspect of this disease while formulating the optimal management of these patients to improve their quality of life.[13] It comprises 10 simple questions to evaluate the impact of disease, covering various topics related to symptoms, change in habits, hobbies, clothing style, work, leisure and social activities, treatment, etc. The answer to each question is graded on a scale of 0–3, depending upon the response (3 = very much, 2 = a lot, 1 = a little, and 0 = not relevant). Thus, the final score ranges from 0 to 30, depending upon the degree of impairment in quality of life. And DLQI score >10 indicates the severe impact of the disease.

Scoring system for special sites (nails)

Around half of the patients having psoriasis are expected to have nail involvement, and involvement of highly visible areas like the face, hands and nails can have a huge psychological burden and severely impact the quality of life of the patient.

Nail Psoriasis Severity Index

In 2003, Rich P et al.[14] proposed an objective, reproducible and simple numeric grading system for evaluating nail psoriasis. In this score, the nail plate is divided into quadrants by drawing imaginary longitudinal and horizontal lines. Each quadrant of the nail is then evaluated for the presence of nail matrix disease (pitting, leukonychia, red spots in lunula, nail plate crumbling) and for nail bed disease (oil drop [salmon patch] discolouration, onycholysis, nail bed hyperkeratosis and splinter haemorrhage). Each nail is scored for nail bed and nail matrix psoriasis, respectively, on a 0–4 scale, depending on the presence of the features of nail psoriasis in that quadrant [Figure 2]. The nail psoriasis severity score is denoted by the sum of the scores obtained from all of the fingernails, which could vary from 0 to 80.

Figure 2.

PASI-high discrimination (PASI-HD) Score graphic representation

Scoring system for special clinical variants of psoriasis

Because none of the available scales for assessing the severity of psoriasis address the presence of pustules or systemic inflammation, which is a hallmark of this variant. There was a need to develop a validated disease measure for pustular psoriasis. Recently,[15,16] the use of new scales to evaluate the severity of generalised pustular psoriasis has been reported.

Generalised Pustular Psoriasis Physician Global Assessment (GPPGA) and Generalised Pustular Psoriasis Area and Severity Index (GPPASI)

These have recently been developed to specifically assess patients with GPP. In both GPPGA and GPPASI, there are five grades of severity for erythema, scaling and pustulation each (0 = clear, 1 = almost clear, 2 = mild, 3 = moderate, and 4 = severe.) The GPPGA score is based on averaging the individual scores for erythema, scaling and pustulation. However, for GPPASI, the score for each body region is calculated (the product of the sum of severity scores and its corresponding BSA score for erythema, scaling and pustulation, multiplied by a weighting factor for each body region as used in classic PASI scoring, the only difference being the replacement of induration by pustulation), and then the total GPPASI score is calculated by adding the individual body region scores.[17]

Conclusion

According to various published systematic reviews, it is clear that no single instrument has been developed for psoriasis, and none of the severity scores currently being used for psoriasis meet all the validation criteria required for an ideal assessment instrument.[18] At the moment, it is prudent to combine two or more scores to satisfy all needs. Thus, continued research efforts are still required to validate existing scores as well as develop newer and better ones. An internationally collaborative approach is needed to reach a consensus on the relevant outcome measures that are universally accepted, as adopted by other specialities of medicines, namely psychiatry and rheumatology.[19]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.