Pasi

Synonym(s)

Psoriasis Area and Severity Index

History
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Fredriksson and Petterson, 1978

Definition
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Best-known, well-standardized index scale (scoring system) for diagnosing and determining the severity of psoriasis. Frequently used in everyday clinical practice to document admission and discharge findings in psoriatic patients as well as for endpoint monitoring in clinical trials or approval studies. The classification of the PASI is important for deciding on systemic or local therapies.

Severity classification of psoriasis - from the current German S 3 guideline (https://www.awmf.org/uploads/tx_szleitlinien/013-001l_S3_Therapie-Psoriasis-vulgaris_2021-07.pdf)

Mild: moderate-severe:

PASI <= 10 and PASI > 10

BSA <= 10 and BSA > 10

DLQI <= 10 DLQI > 10

An upgrade of the mild form according to PASI calculation can result from infestation of sensitive areas (scalp, ano-genital region, nail infestation) or resistance to therapy.

Further PASI values:

PASI 75 is a dynamic parameter that is used to monitor systemic therapy for psoriasis. It describes the percentage improvement in the PASI index, i.e. a 75% reduction in the PASI index compared to the initial value.
Corresponds to PASI 90 or PASI 100.

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General information
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The PASI was originally developed as a target for efficacy studies of retinoids in patients with chronic plaque psoriasis. In recent years, the method has become the gold standard for target values in clinical studies on psoriasis.

The aim of the PASI is to document the area and severity of the skin lesions. The PASI consists of an area and a dermatological component.
The affected area (A) is determined separately for the head, trunk, upper and lower extremities. A numerical scale is used (0 = no involvement, 1 = < 10%, 2 = 10 to < 30%, 3 = 30 to < 50%, 4 = 50 to < 70%, 5 = 70 to < 90% and 6 = 90-100%).
In the dermatological section, erythema (E = erythema), infiltration (I = infiltration) and desquamation (D = desquamation) are rated on a scale from 0 to 4. The head (K = head; h = head) is weighted with 0.1, the trunk (R = trunk; t = trunc) with 0.3, the upper extremity (A = arms; u = upper limb) with 0.2 and the lower extremity (B = legs; l = lower limb) with 0.4.

Scheme for determining the PASI
The PASI can take values from 0 to 72 and is calculated as follows:
Calculation of the indices for the individual body sections	K = 0.1 x (EK + IK + DK) x AK
	A = 0.2 x (EA + IA + DA) x AA
	R = 0.3 x (ER + IR + DR) x AR
	B = 0.4 x (EB + IB + DB) x AB

PASI = K + A + R + B	0.1 x (EK + IK + DK) x AK
	+ 0.2 x (EA + IA + DA) x AA
	+ 0.3 x (ER + IR + DR) x AR
	+ 0.4 x (EB + IB + DB) x AB

Repeated determination of the PASI or the indices of the individual body sections can be used to document the intra-individual course of the disease as well as for comparison with other patients.

Note(s)
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Remember! The application of the PASI-Score has found a wide spread use in in-patient treatment and also in out-patient treatment. Decisive for its application under outpatient conditions was, apart from the documentation of the therapy success, above all the definition of the proof of medium to severe psoriasis for the balneo-phototherapy to be carried out on an outpatient basis, as determined by the Federal Joint Committee. For the billing of the balneo-phototherapy (bath-PUVA-therapy or photo brine-therapy) a PASI-Score > 10 has to be proved here.

Literature
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Feldman SR et al (1996) The self-administered psoriasis area and severity index is valid and reliable. J Invest Dermatol 106: 183-186
Fredriksson T, Petterson U (1978) Severe psoriasis-oral therapy with a new retinoid. Dermatologica 157: 238-244
Sampogna F et al (2003) Performance of the self-administered psoriasis area and severity index in evaluating clinical and sociodemographic subgroups of patients with psoriasis. Arch Dermatol 139: 353-358
Shikiar R et al. (2003) Validity and reliability of patient reported outcomes used in psoriasis: results from two randomized clinical trials. Health and Quality of Life Outcomes 1: 53
https://www.awmf.org/uploads/tx_szleitlinien/013-001l_S3_Therapie-Psoriasis-vulgaris_2021-07.pdf

Tables
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Scheme for determining the psoriasis area and severity index (PASI score)

Name of the patient:
Date of birth:												Date of diagnosis:

Severity of the psoriatic lesions
Please circle the appropriate numerical value for each of the following efflorescences and localizations according to the degree of expression! Degree of efflorescence: (0 = no efflorescence or no infestation; 1 = mild infestation; 2 = moderate infestation; 3 = severe infestation; 4 = very severe infestation)
		Localization
Line number	Efflorescence	Head					Fuselage						Arms					Legs
		state of expression					state of expression						state of expression					state of expression
1	Erythema	0	1	2	3	4	0	1	2	3	4		0	1	2	3	4	0	1	2	3	4
2	Infiltration	0	1	2	3	4	0	1	2	4	4		0	1	2	3	4	0	1	2	3	4
3	Scaling	0	1	2	3	4	0	1	2	3	4		0	1	2	3	4	0	1	2	3	4
4	Total

Infestation of the body surface
Please note the area infested in line 6 for the respective localisations. Circle the appropriate numbers before the percentages corresponding to the infested area. Infested body surface: (0 = no infestation; 1 = < 10% infected area at the location; 2 = 10-29% infected area at the location; 3 = 30-49% infected area at the location; 4 = 50-69% infected area at the location; 5 = 70-89% infected area at the location; 6 = 90-100% infected area at the location)
Line number		Localization
5			Head						Fuselage						Arms					Legs
			infested area						infested area						infested area					infestedarea
6	Infested area		0	no head injury					0	no infestation of the fuselage					0	no infestation of the arms				0	no infestation of the legs
			1	< 10% infested					1	< 10% infested					1	< 10% infestation				1	< 10% infested
			2	10-29% infested					2	10-29% infested					2	10-29% infested				2	10-29% infested
			3	30-49% infested					3	30-49% infested					3	30-49% infested				3	30-49% infested
			4	50-69% infested					4	50-69% infested					4	50-69% infested				4	50-69% infested
			5	70-89% infested					5	70-89% infested					5	70-89% infested				5	70-89% infested
			6	90-100% infested					6	90-100% infested					6	90-100% infested				6	90-100% infested
7	Product of lines 4 + 6
8	Factors of the basket surface		x 0,10						x 0,30						x 0,20					x 0,40
9	Product of lines 7 + 8
10	PASI-Score = sum of line 9