Clinical skin and joint manifestations of the chronic autoimmune diseases psoriasis (psoriasis) and psoriatic arthritis (psoriatic arthritis) not only have a major impact on health-related quality of life of the patients,1 but also represent a substantial economic burden on health systems.2,3 Psoriasis generally follows a chronic course, with relapses associated with different skin manifestations.4 Psoriatic arthritis is a chronic disease affecting the musculoskeletal system. It is usually seronegative and may be associated with psoriasis.5 Patients with psoriatic arthritis usually but not always present with skin manifestations before joint involvement is apparent,6 and in approximately 80% of patients, the presence of psoriasis occurs before the onset of psoriatic arthritis7 with a lag usually in excess of 10 years from diagnosis of psoriasis.6 In addition, although there is no clear correlation, there appears to be a greater risk of psoriatic arthritis in patients with more severe forms of psoriasis.7

The prevalence of these diseases is not well defined, given the heterogeneity of the clinical manifestations and differences in the diagnostic and classification criteria.9–11 Estimates of the prevalence of psoriasis and psoriatic arthritis range from 1.3% to 2.2% and from 0.3% to 1% of the population, respectively.6,8 In Spain, although the number of studies is limited, according to estimates from recent data, the prevalence of psoriasis lies between 1.2% and 2.3%,12,13 and the prevalence of psoriatic arthritis is estimated to be 0.17%.12 Furthermore, the prevalence of psoriatic arthritis in patients with psoriasis in Europe is significant, ranging from 9.8% in the Spanish population12 to 13.8% in the United Kingdom.14

The therapeutic approach to psoriasis and psoriatic arthritis is broad-ranging, and includes a first stage with conventional therapy (topical agents, phototherapy, glucocorticosteroids, nonsteroidal antiinflammatory agents, and nonbiologic disease modifying antirheumatic drugs) and a second stage with biologic therapies in patients refractory to conventional therapy.8,15,16

Although a dose-dependent relationship between the use of biologic agents and the risk of infection has recently been observed,3 such agents are extremely effective and have considerably improved health-related quality of life.8 The counterpoint to this improvement is that the introduction of new biologic agents may increase the economic burden associated with these diseases.2,8 Thus, the objective of this study was to review the studies of costs of psoriasis and psoriatic arthritis management in the 5 biggest economies in Europe (Germany, Spain, France, Italy, and the United Kingdom).

We retrieved 775 publications, 529 (68.3%) about psoriasis and 246 (31.7%) about psoriatic arthritis. During the selection process, 761 publications were excluded because they were duplicates or did not meet the inclusion criteria (Fig. 1). Finally, 14 publications were included, 10 related to the cost of psoriasis (n=5,537 patients) and 4 to psoriatic arthritis (n=3,828 patients).

Figure 1.

Flow diagram for the process of study selection based on PRISMA criteria.

Ps indicates psoriasis; PsA, psoriatic arthritis.

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Cost of psoriasis

The annual cost of psoriasis, regardless of severity, lay between US $2,077 and $13,132PPP patient-year,30,31 excluding studies of biologic agents,23,25 and a study that assessed only hospitalized patients.29 The direct and indirect costs ranged from US $1,715 to $8,925 and from US $364 to $4,207 PPP patient-year, respectively (Table 4). The direct costs were those that accounted for the greatest proportion of the total cost (between 50% and 93%), with the maximum proportion reported in a Spanish study (Fig. 2A).31

Table 4.

Cost of Psoriasis.

Author, Year of Publication (Price Year)	Population	Original Costs (Patient-Year, €Year Costs)			Δ HICP Applied19	Updated Costs (Patient-Year, euros in 2015)			Current Costs Adjusted for PPP20 (Patient-Year, PPP USD 2015)
		Direct Costs	Indirect Costs	Total Cost		Direct Costs	Indirect costs	Total cost	Direct costs	Indirect costs	Total cost
Germany
Berger et al., 200526a (€2002)	Generalized Ps	1,426	1,440	2,866	21.9%	1,738	1,755	3,494	2,217	2,239	4,456
	Moderate Ps	1,393	1,266	2,658		1,698	1,543	3,240	2,166	1,968	4,133
	Severe Ps	1,423	1,429	2,852		1,735	1,742	3,477	2,213	2,222	4,434
Schöffski et al., 200728 (€2006)	Moderate to severe Ps	5,397	1,310	6,707	14.3%	6,169	1,497	7,666	7,868	1,910	9,778
Lang et al., 200929 (ND)(€2009)	Hospitalized Patients	9,510	2,973	17,458	8.5%	10,318	3,226	18,942	13,161	4,114	24,161
	Outpatients	1,850	509	7,657		2,005	552	8,297	2,560	704	10,597
Steinke et al., 201322 (€2006)	Generalized	5,576	1,515	7,092	14.3%	6,373	1,732	8,106	8,129	2,209	10,339
	Hospitalized Patients	10,070	2,973	13,042		11,510	3,398	14,907	14,681	4,334	19,014
	Outpatients	2,476	509	2,985		2,830	582	3,412	3,610	742	4,352
Spain
Carrascosa et al., 200630 (€2003)	Generalized	891	189	1,079	27.8%	1,139	242	1,379	1,715	364	2,077
	Mild	775	118	893		990	151	1,141	1,492	227	1,719
	Moderate	1,028	245	1,265		1,314	313	1,617	1,979	472	2,435
	Severe	1,574	595	2,169		2,012	760	2,772	3,029	1,145	4,175
Sanchez-Carazo et al., 200931 (ND; €2009)	Moderate to severe Ps	6,420	461	6,881	8.3%	6,953	499	7,452	10,471	752	11,223
France
Le Moigne et al., 201423 (ND, €2012)	Before BA	1,586	105	1,678	1.7%	1,613	107	1,707	1,967	130	2,081
	After BA	8,111	28	8,107		8,249	28	8,245	10,060	35	10,055
Italy
Finzi et al., 200124 (€1994)	Generalized	905	No	905	59.3%	1,442	No	1,442	1,938	No	1,938
Colombo et al., 200827 (€2006)	Generalized	5,690	2,682	8,372	16.7%	6,640	3,130	9,770	8,925	4,207	13,132
	Moderate	3,643	1,583	5,226		4,251	1,847	6,099	5,714	2,483	8,197
	Severe	7,683	3,751	11,434		8,966	4,377	13,343	12,051	5,884	17,935
United Kingdom
Fonia et al., 201025b (£2008)	Before BA	4,207£/5,283€	No	4,207£/5,283€	18.1%	4,968£/6,239€	No	4,968£/6,239€	7,097	No	7,097
	After BA	11,891£/15,046€		11,891£/15,046€		14,043£/17,769€		14,043£/17,769€	20,061		20,061

Abbreviations: BA, biologic agents; HICP, harmonized index of consumer prices; ND, no data; PPP, purchasing power parity; Ps, psoriasis.

a

Includes a group of patients with arthritis (2358€ of total costs when patients with arthritis are excluded).

b

Price given in pounds Sterling in the original article. Cost estimate in euros with the reference exchange rate published by the Central European Bank in 2008 (according to publication) Available from: http://sdw.ecb.europa.eu/quickview.do?SERIES_KEY=120.EXR.A.GBP.EUR.SP00.A.SortOrder=ASC

Figure 2.

Percentage of direct and indirect costs by total cost per patient-year (according to current costs, US$ PPP 2015). A, Psoriasis. B, Psoriatic arthritis.

Two studies of psoriasis conducted in France23 and the United Kindgom25 and 1 study of psoriatic arthritis conducted in Italy33 were excluded because they only assessed exposure to biologic agents.

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An increase in costs was seen in those studies that analyzed patients with severe disease (direct, indirect, and total cost between US $2,213 and $12,051, $1,145 and $5,884, and $4,175 and $17,935PPP patient-year, respectively). When the costs were assessed by grouping patients with moderate to severe psoriasis, the direct and total costs were similar (US $7,868-$10,471 and $9,778-$11,223 PPP patient-year, respectively), with the highest costs corresponding to the study conducted in Spain.31

The total cost of hospitalized patients was analyzed in 2 German studies, with the direct and total costs exceding those of the other studies included in this review (US $13,161-$14,681 and $19,014-$24,161PPP patient-year, respectively).22,29

In addition, the direct costs for management of psoriasis increased by 3-fold to 5-fold after administration of a biologic agent (before the biologic agent: US $1,967 to $10,060 PPP patient-year; after the biologic agent: US $7,097 to $20,061 PPP patient-year), due to an increase in pharmacological costs (before the biologic agent: US $412 to $8,013 PPP patient-year; after the biologic agent: US $2,111 to $18,064 PPP patient-year) with a similar impact on total costs (Fig. 3A).23,25

Figure 3.

Impact of introduction of biologic agents (BA). A, Percentage of costs before and after exposure to BA in psoriasis. B, Percentage of costs before and after exposure to BA in psoriatic arthritis. C, Variation (in percent) of costs before and after exposure to BA in psoriatic arthritis.

aPercentage of costs associated with patients with plaque psoriasis. The patients received treatment with systemic nonbiologic agents and topical agents before and after treatment with biologic agents.

bPatients with moderate to severe psoriasis. The pharmacological cost of patients treated with BA also includes other systemic drugs.

cPatients with psoriatic arthritis with failure or intolerance of conventional therapy. The percentage of costs after starting BA-based treatment was calculated from the increment in cost and cost before starting with BA.

dExpresses the incremental cost in patients treated with BA compared to an earlier period.

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The results of this study suggest that, in Europe, psoriasis and psoriatic arthritis are associated with a substantial economic impact. The annual cost of managing a patient with psoriasis is variable and in line with previously published reviews,2,35 except for the annual cost in Sweden, which was greater (11,928€ —in euros 2009—equivalent to US $14,820PPP).2

Except for 2 German studies,26,34 the direct costs account for the greatest part of the total cost from the societal perspective, both in psoriasis (6 studies) and psoriatic arthritis (2 studies). Spain was the country with the lowest annual direct costs per patient in psoriasis and the highest costs in psoriatic arthritis.

According to the present study, a directly proportional relationship between the severity of disease and the associated cost can be established, driven mainly by an increase in direct costs. In one of the reviews mentioned above,35 an increase (of up to 2.5-fold) in the cost of management of severe psoriasis compared with moderate psoriasis was detected, driven mainly by the greater resource consumption and associated loss of productivity.

Although the introduction of biologic agents seems to have led to a reduction in hospital costs for the management of psoriasis, with a decrease of 2,357€ vs 564€ patient-year (euros 2013, equivalent to US $2,902 to $695PPP patient-year),35 the increase in direct and total cost identified in the studies of psoriasis and psoriatic arthritis23,25,33 showed the huge economic impact of their incorporation into the therapeutic arsenal. The effect of introducing biologic agents in Europe has been evaluated previously.36–38 The usage of the different biologic agents available for treatment of moderate to severe psoriasis in Spain was associated with a total cost between 12,120 and 18,370€ patient-year (euros 2010, equivalent to US $19,385 and $29,381PPP patient-year).36 In the Netherlands, the inclusion of biologic agents increased the cost of management of psoriasis to 17,712€ from 10,146€ (euros 2010, equivalent to US $23,791 and $13,628PPP patient-year, respectively).37

In Italy, the cost of treating patients with psoriatic arthritis refractory to nonbiologic systemic disease modifying antirheumatic drugs and those treated with anti-TNF agents for 5 years was assessed, showing a significant increase in direct costs due to pharmacological expenditure on anti-TNF agents. This increase was slightly offset by a decrease in indirect costs.38

One of the possible limitations of this review is the variability in the methodology used in the studies (study population, sample size, follow-up duration, perspective used, year of costs assessed) and this might hinder comparison of results and thus extrapolation of conclusions.

Assessment of the methodological quality of the studies included with the CHEERS criteria21 identified considerable differences among studies. Some publications were presented in the form of congress absracts,29,31,32 without any corresponding full-text article in a scientific journal. This limits the amount of information available and may explain the high rate of noncompliance found in the CHEERS assessment. Another critical item missing in some publications was the date of costs.23,24,29,31 This shortcoming was addressed using the year of data collection,23,24 or the date of publication.29,31 Thus, the presentation of costs with different dates and currencies could be a serious limitation for comparability of the results. However, adjustment for increased harmonized index of consumer prices19 and the subsequent conversion to the currency of current international Dollars (US$ PPP2015)20 has eliminated differences in the prices between countries and, therefore, balances the purchasing power of different currencies, making the comparison more feasible.39

Another difference to consider is the use of different methods for the calculation of indirect costs. On the one hand, the friction costs method assesses the loss due to absence from work by estimating the cost required to replace the worker.40 By contrast, the human capital method measures future monetary productivity of individuals who benefit from a health activity, for example, pensions that do not need to be paid to prevent occupational diseases or the work days that are not lost.41 The use of one or other method may have an impact on total cost, as observed in a publication on psoriatic arthritis that showed a substantial increase in indirect costs when the human capital method was used to calculate indirect costs.34

Another possible limitation of the present study is the small number of publications identified, as although the PRISMA criteria were applied17 and the PubMed and EMBASE databases were used, other sources of grey literature were not assessed (see Annex 1).

Furthermore, it may be supposed that clinical management of psoriasis and psoriatic arthritis has changed considerably in recent decades, mainly as a result of the introduction of biologic agents in everyday clinical practice. Given that the most recent study reviewed here collected data in 2011,23 the current costs of the diseases may actually be higher.

The low number of analyses focused on estimating the cost of psoriasis or psoriatic arthritis points to the need for and importance of future studies of the cost of the disease. These studies should reflect clinical practice and provide useful and up-to-date information for decision making in health care, in light particularly of the arrival of biosimilar biologic agents for the management of these 2 diseases.

In conclusion, despite the limitations mentioned above, a review of the studies included shows the high economic impact of treatment and management of psoriasis and psoriatic arthritis. Costs increase with increasing severity and in particular with the use of biologic agents.

Celgene S.L. provided unconditional funding for conducting this project.

MTC is an employee of Celgene. RBP, IE, and MAC are employees of Pharmacoeconomics & Outcomes Research Iberia (PORIB), which received unconditional financial support for writing the present manuscript. JMMS has received fees from PORIB for collaboration and consultation in this project. JMVC declares no conflict of interest and has received no fees for participation in or contribution to the present study.