Psoriasis produces a wide variety of clinical signs and has a considerable impact on the patients’ quality of life, which requires tools that accurately reflect the severity of the disease and its implications.

The Psoriasis Area and Severity Index (PASI), defined by Fredriksson and Pettersson in 1978,1 has become the reference method for measuring the severity of psoriasis. It allows for standardized therapeutic decision-making in psoriasis that require systemic treatment and evaluates the response to treatment. However, this scale has never been adequately validated2 and presents limitations such as the lack of inclusion of the symptoms caused by the disease, the absence of utility in forms such as pustular psoriasis, arithmetic complexity, the need to estimate body surface area—with high intra- and inter-observer variability—lack of standardization of cutoff values for mild, moderate, and severe psoriasis, the need to resort to other scales to understand its psychosocial impact (Dermatology Life Quality Index, DLQI), and the limited importance it places on the distribution of lesions in areas with greater psychosocial or functional burden.

All this makes requires a new tool that allows for a more objective, simple, and comprehensive assessment of patients with psoriasis. The Simplified Psoriasis Index (SPI), developed in the United Kingdom,2 has been translated and validated into several languages,3–6 with promising results that encourage its use in our routine clinical practice for both children and adults.7

This scale does not require numerical calculation of the affected body surface area, includes an assessment of the patient's psychosocial sphere, and is easily reproducible. Additionally, it allows for better assessment of “special locations”; even if the patient has a small diseased surface area, these location will be categorized into the moderate or severe psoriasis group when lesions affect visible, bothersome, or hard-to-treat areas, such as face, palmoplantar area, axillary and groin folds, or genital area.

For all these reasons, this study aims to assess the clinical applicability of the SPI by studying the results obtained from using its Spanish-translated version in our real clinical practice.

The study included a total of 45 patients, with a mean age of 51 years (95%CI, 46.11–55.90) and a mean duration of psoriasis of 14.05 years (95%CI, 9.07–19.03). Additionally, 26.6% exhibited associated psoriatic arthritis. Regarding clinical severity, they had mean PASI values of 4.51 (95%CI, 2.72–6.30) and mean proSPI-s and saSPI-s scores of 3.78 (95%CI, 2.36–5.21) and 5.12 (95%CI, 3.11–7.13), respectively. The mean DLQI value was 6.62 (95%CI, 4.21–9.03) and the SPI-p was 2.95 (95%CI, 2.23–3.68).

To evaluate criterion validity, the Spearman rank correlation coefficient was calculated between the gold standard and the SPI different modalities: a good correlation was observed between the PASI and proSPI-s (r=0.89) and between the DLQI and SPI-p (r=0.89). However, the correlation level between PASI and saSPI-s (r=0.52) was only moderate in the obtained sample (Table 1).

To evaluate the concordance of the 2 modalities of the SPI scale, the intraclass correlation coefficient (ICC) was calculated between the proSPI-s and saSPI-s values of each of the studied locations, yielding values<0.75 (moderate reliability) in the face, neck, and ears (0.72); arms and armpits (0.63); chest and abdomen (0.74); anogenital area (0.68); buttocks and thighs (0.72); knees, lower legs, and ankles (0.74).

The use of the validated Spanish version of the SPI scale in then routine clinical practice allows for a comprehensive assessment of psoriasis by simplifying the calculation of the diseased surface area in each location by giving equal weight to each. Additionally, it includes an assessment of the psychosocial impact in the form of a visual analog scale, which is simple and quick. In the initial development by Chularojanamontri et al., a good correlation between the proSPI—criterion validity—and the reference criterion—PASI—was observed, as well as a good correlation between SPI-p and the DLQI, which is consistent with the results seen in this study. However, the correlation observed between saSPI-s and PASI is not as intense, not even compared to the validation study of the scale in Portuguese (Table 2).

To understand these results, we considered the possibility that some locations were being systematically undervalued by the professional. The SPI scale breaks down into 10 body areas, allowing special locations to have a greater weight than in PASI. When calculating the ICC between proSPI-s and saSPI-s for each of the studied locations, we obtained moderate reliability values in certain locations. Notably, the ICC was lower, on one hand, in the anogenital area (0.68), a region that is often not thoroughly explored in the routine clinical practice despite the impact it has on disease severity; and on the other hand, although less expected due to being a much more accessible location for examination, in arms and armpits (0.63). This disparity could partly justify the lower correlation reported between saSPI-s and PASI, although the published evidence to date does not include this information, so further studies with a larger number of patients and a breakdown by locations would be necessary to corroborate this hypothesis.

Limitations include the small number of patients included in the study sample and the lack of prospective follow-up, which prevents us from studying the scale across the patient's clinical progression. Additionally, the good disease control that the participants included in the study generally present implies that they have a relatively low PASI. This circumstance may have partly conditioned the results obtained.

This study describes the first results of the use of the validated Spanish version of the SPI in real clinical practice, showing a good correlation between the SPI-s performed by the professional and the PASI scale, and between the psychosocial assessment and the DLQI. The simplicity of its calculation and its integrative nature, along with the evaluation of the disease natural history make the use of this scale promising for our clinical practice. The use of the saSPI scale could be a useful tool for remote monitoring of patients with psoriasis, although its poorer correlation with the PASI poses a limitation.

None declared.