Abstract
Background
Psoriasis is a prevalent, chronic skin disease with a potential impact on work productivity, medical consumption costs, and quality of life. The influence of the extent of skin lesions on these outcomes is not well known.
Objective
We determined associations of self-reported skin lesions with self-reported work productivity, medical consumption costs, and health-related quality of life in respondents with psoriasis.
Methods
In this cross-sectional study, we included respondents with self-reported psoriasis in the Netherlands in an online questionnaire. We assessed the self-reported percentage body surface area (BSA) of psoriasis lesions. We used validated instruments to assess work productivity (WPAI-PsO), medical consumption costs (iMCQ), and health-related quality of life (EQ-5D-5L and the DLQI). We used ordinal logistic regression to associate BSA categories >1% versus 0-1% with outcomes adjusted for multiple confounders.
Results
We included 501 respondents with a mean age of 43 ± 12 years; 64% were men. Median BSA was 2% (interquartile range 1–5%). A higher BSA was associated with higher overall work impairment due to psoriasis (common odds ratio [cOR] 2.44, 95% confidence interval [CI] 1.40–4.29; n = 205), higher medical consumption costs (cOR 2.06, 95% CI 1.45–2.94) and lower health-related quality of life. Associations were strongest with a BSA cutoff of 0% or 1% compared to 2% or higher categories.
Discussion
In our study, having few to no lesions in psoriasis was associated with lower overall work impairment due to psoriasis, lower medical consumption costs, and higher health-related quality of life.
1. Introduction
Psoriasis is a chronic inflammatory skin disease. Patients often have comorbid diseases, experience low psychosocial functioning and have a low quality of life (Citation1–3). Psoriasis is especially prevalent in Western countries with a prevalence of ∼2–3% (Citation4,Citation5) and may start already in adolescence, affecting predominantly the working population. It may pose a substantial economic burden on society through high medical consumption costs (Citation6), as well as loss of work productivity (Citation7,Citation8). Medical costs, productivity impairment and risk factors could vary over time due to changes in disease management, and per country (Citation7). For the Netherlands, only one cross-sectional outpatient study in young adults assessed the association between the impact of psoriasis with medical costs and productivity impairments (Citation9).
One factor potentially driving costs and productivity impairment is the extent of skin lesions in psoriasis (Citation10), a clinical indicator of disease severity (Citation11,Citation12). As the extent of lesions is amenable to treatment, determining whether the extent of skin lesions in psoriasis impacts work productivity and medical consumption cost would provide actionable insights to reduce the economic and societal burden of the disease.
For the extent of lesions in psoriasis, prospective studies from a clinical setting indicate that there is a threshold which best reflects severity (Citation13,Citation14). These studies indicate that only achieving few to no skin lesions compared with a higher lesion load was associated with good psychosocial functioning and quality of life, and could be considered a desirable treatment goal (Citation13,Citation14). While the extent of lesions is important, it may not always align with other severity indices of psoriasis such as impairment of quality of life or daily functioning (Citation15). Combining multiple disease measurements may better capture the severity of psoriasis (Citation16).
In this cross-sectional questionnaire-based study, we determined the association of self-reported skin lesions as assessed by body surface area (BSA) with self-reported work productivity, medical consumption costs, and health-related quality of life, in the Netherlands. We hypothesized that more lesions were associated with lower outcomes. We also explored if treatment goals were defined.
2. Patients and methods
2.1. Study setting and population
We conducted a cross-sectional, online questionnaire study in respondents with self-reported psoriasis in the Netherlands. Respondents were recruited by an online questionnaire provider, Dynata (www.dynata.com), which aims to provide a representative sample of the Dutch population for age, sex, education, and region. All Dynata members had to report prespecified prevalent health conditions including psoriasis. The psoriasis prevalence in the Dynata sample is approximately 1%. Respondents were incentivized to share information by receiving questionnaires relevant for their situation, and after completion of the survey received points redeemable in cash. Respondents were blinded to the questionnaire topic at entry.
We aimed to include a sample of ≥225 respondents based on a difference between moderate versus severe psoriasis of 10.8% for the outcome overall work impairment due to psoriasis in a cross-sectional, multi-country survey (alpha = 0.05, beta = 0.2) (Citation7).
The study was approved by the relevant Dutch institutional review board (non-WMO, Toetsingskader niet-WMO plichtig onderzoek), reference number NWMO22.04.009. All participants provided written informed consent for participation in this study. We used the STROBE reporting guidelines for cross-sectional studies.
Data collection took place from 13 to 27 July 2022. We included respondents who (i) provided informed consent, (ii) re-confirmed self-reported psoriasis as having ever been diagnosed by a doctor, and (iii) were aged ≥18 years.
In total, 670 respondents started the questionnaire of whom 625 (93%) were eligible: 10 respondents refused consent, 32 respondents did not have self-reported psoriasis, and 3 respondents were aged <18. Furthermore, 74 respondents (11%) dropped out due to e.g., technical difficulties, 48 respondents (7%) were excluded by Dynata due to suspected fraudulent or low-quality data, and 2 respondents were excluded after manual quality checks. The analytical sample consisted of 501 respondents. The included respondents were approximately similar in age (43.1 versus 41.3 years) and did not differ by sex (63.9% versus 63.9% female) compared to the 169 excluded respondents.
2.2. Questionnaire
The online questionnaire combined 4 validated questionnaires on work productivity, medical consumption, and health-related quality of life with additional questions on treatment goals, and overall treatment satisfaction in the past year (See Online Appendix S1, part I for consolidated details of the questionnaire). The electronic questionnaire was tested by qualitative interviews with 2 patients, and further piloted in 20 participants to optimize wording and programming. Programming enforced completing all questions, thereby limiting missing data.
2.3. Extent of skin lesions – body surface area
We measured the extent of skin lesions through self-report. The overall lesion size was estimated relative to total BSA, using the size of the respondents’ own handprint (palm plus fingers) as a proxy for representing 1% of total BSA. Respondents were asked to estimate the total size of psoriatic lesions through the number of handprints (Citation17). We dichotomized BSA into 0-1% (having ‘clear’ or ‘near-clear’ skin) versus >1%. Self-reported BSA is a valid and feasible measure for this study (details in Online Appendix S1, part II).
2.4. Outcome measures
We included 4 questionnaires on the following topics: work productivity (Work Productivity and Activity Impairment Index [WPAI]), medical consumption (Institute of Medical Technology Assessment Medical Cost Questionnaire [iMCQ]), health-related quality of life (EuroQol-5D-5L [EQ-5D-5L] and Dermatological Life Quality Index [DLQI]).
The WPAI assesses productivity at work over the past 7 days through 6 items (Citation18,Citation19). Using descriptions of hours of the workweek and visual analogue scales, it allows to calculate the overall work impairment due to psoriasis and secondary parameters. Overall work impairment due to psoriasis could only be calculated for respondents working for pay in the last week.
The iMCQ assesses medical consumption in the past 3 months specific to the Dutch healthcare system (Citation20). A corresponding costing manual allows for calculation of a 3-month total estimate of direct healthcare costs. Costs were inflation-corrected for the year 2021 using the Dutch consumer price index. We queried all concomitant treatments including medication for psoriasis in prespecified categories (e.g., topical treatments) and not on molecule level.
The EQ-5D-5L assesses health-related quality of life through 5 items on a 5-point scale (Citation21). Based on the 5 responses, we calculated an overall health utility score (1 represents perfect health, 0 represents death, and scores below 0 reflect health states considered worse than death) (Citation21) using Dutch reference utility values (Citation22). The EQ-5D also queries overall health status by a visual analogue scale (EQ-VAS, scored 0-100) with higher scores indicating better health.
The DLQI assesses health-related quality of life specific to dermatoses (Citation23). It consists of 10 items scored 0–3 (sum scores 0–30), evaluating impact on various domains over the past week. Higher scores indicate lower health-related quality of life (details in Online Appendix S1, part I).
All questionnaires have shown acceptable validity and reliability (Citation18,Citation23,Citation24).
Lastly, we assessed (i) whether treatment goals were specified for the current treatment between respondent and physician; (ii) if treatment goals were not specified whether this was problematic; (iii) type of treatment goals discussed according to prespecified categories; (iv) whether treatment goals were achieved; (v) treatment satisfaction (Online Appendix S1, part III).
2.5. Covariates
The questionnaire started with demographic questions on year of birth, sex, education (low, medium, or high), and occupation (paid employment/school going yes/no) We also queried year of diagnosis of psoriasis, and presence of prespecified comorbidities (Online Appendix S1, part I).
2.6. Statistical analysis
All outcome measures (overall work impairment due to psoriasis, overall medical consumption cost, EQ-5D-5L utility score, and total DLQI score) were non-normally distributed (Figure S1). We categorized outcomes in 3 equal categories except for medical consumption cost 4 categories). We tabulated demographics by BSA categories >1% vs. BSA 0–1%.
We used ordinal logistic regression to associate BSA >1% vs. BSA 0–1% with the ordinal outcomes, reported through common odds ratios [cOR] and 95% confidence intervals.
An ordinal approach was chosen to allow analyzing the different, non-normally distributed outcomes with one single analytical model, while retaining as much information in the outcomes as possible as opposed to dichotomizing outcomes and using logistic regression. We found no violations of proportional odds assumption for the primary analyses. We adjusted analyses for potential confounders: age, sex (model 1) and additionally for education, years since first diagnosis of psoriasis, and number of comorbidities (model 2).
We associated BSA with overall work impairment and medical consumption costs. As sensitivity analysis, we repeated this analysis with BSA 0% vs. >0%, and 0–2% vs. >2%.
Furthermore, we determined the associations of BSA with total DLQI score and EQ-5D-5L health-utility score. Also, we used both BSA and total DLQI scores to assess a different construct of the severity of psoriasis (Citation25) and determined the association with all outcomes, except DLQI. For this combined score, severity was categorized as low (BSA ≤ 5% and DLQI score ≤5), or moderate-high (BSA > 5% or DLQI score > 5). Further, we determined associations of BSA with secondary outcomes: (i) hours of work time lost to psoriasis, (ii) impact of psoriasis on productivity during work, (iii) impact of psoriasis on daily functioning, and (iv) the EQ-VAS.
Lastly, we described setting treatment goals, and the overall treatment satisfaction in the past year.
Data management and statistical analyses were performed with IBM SPSS Statistics version 28 (IBM Corp, Armonk, N) and R software version 2022.07.0 (packages: polr).
3. Results
3.1. Study population
We included 501 respondents with a mean age of 43 ± 12 years, of whom 64% were male (). Median BSA was 2% (IQRs 1–5%, distribution in Figure S1); n = 143 had a BSA of 0–1%, and n = 358 had a BSA of >1%.
Table 1. Characteristics of study population, overall and stratified by self-reported affected body surface area of skin lesions in psoriasis.
Concomitant treatments were common: 66% used topical treatments, 47% used conventional systemic medication, and 44% used biologics systemic medication (). Forty-four percent had a history of psoriatic arthritis. When looking specifically at the BSA categories: respondents with BSA > 1% were younger (41.2 ± 9.8 vs.47.7 ± 13.9 years), more likely male (70 vs.48%), less often ‘highly’ educated (26% vs. 41%) but did not differ in levels of paid employment/schooling and duration of psoriasis. Respondents with BSA > 1% were more often treated with conventional (55% vs. 26%) or biologic (54% vs. 20%) systemic medication than respondents with BSA 0–1%. Furthermore, respondents with BSA > 1% had a higher frequency of comorbidities including a history of psoriatic arthritis (52 vs.24%), cardiovascular disease (25 vs.13%) and diabetes mellitus (28 vs.10%) than those with BSA 0–1%.
3.2. Outcomes
3.2.1. Work productivity
Most WPAI outcomes were calculated in n = 205 (40.9%) respondents since not all respondents reported working for pay in the past week (; Table S2). These 205 respondents, compared to 179 respondents who had also reported paid employment/going to school but did not fill out the WPAI, were of similar age (41.5 vs. 39.5 years), less often male (60% versus 89%), had a slightly lower BSA (2% versus 3%), lower medical consumption cost (median €222 versus €444), and less often took systemic medication (51% versus 85%). Overall work impairment due to psoriasis had a median score of 58% (IQR 0-87%), and clearly differed between respondents with BSA 0-1% (median 6%) vs. BSA > 1% (median 77%).
Table 2. Patient-reported outcomes on work productivity, medical consumption, and quality of life, overall and stratified by body surface area.
3.2.2. Medical consumption
The median medical consumption cost in the past 3 months was €333 (IQR €0-1373); 26% of respondents reported no costs. Costs for respondents with BSA 0-1% (€138 [IQR €0-428]) were much lower than costs for those with BSA > 1% (€809 [IQR €0-2722]; ).
3.2.3. Health related quality of life
Similarly, health-related quality of life scores were lower for both EQ-5D and DLQI in BSA > 1% (; EQ-VAS in Table S2).
3.3. Primary analysis: overall work impairment, medical consumption costs and health-related quality of life
BSA >1% vs. BSA 0–1% was significantly associated with higher overall work impairment (model 2, cOR 1.94, 1.06–3.58) and with higher medical consumption costs (model 2, cOR 1.92, 1.30–2.85) (). Similarly, we found associations of BSA > 1% with lower health-related quality of life for both the EQ-5D (model 2, cOR 0.49, 0.32–0.73) and total DLQI score (model 2, cOR 2.51, 95% CI 1.63–3.87).
Table 3. Associations of severity of skin lesions in psoriasis with overall work impairment, medical consumption cost, and health-related quality of life.
As sensitivity analysis, we used other BSA categories: 0% vs. >0% and 0–2% vs. >2%. These associations of higher BSA with all outcomes were more pronounced using the 0% cutoff (Supplementary Table 3). Using the 2% cutoff, all estimates attenuated, and associations disappeared except for the association of BSA > 2% vs. BSA 0–2% with higher total DLQI score (Supplementary Table 3).
3.4. Severity of psoriasis assessed by BSA and DLQI
Compared to low severity, moderate-high severity was associated with higher overall work impairment due to psoriasis (cOR 3.80, 2.01–7.30), and with higher medical consumption costs (cOR 2.93, 2.03–4.25; ). We found no associations of the severity of psoriasis defined by both BSA and DLQI with the EQ-5D health utility score (cOR 1.20, 0.80–1.81; ).
Table 4. Associations of psoriasis severity determined by BSA and DLQI with overall work impairment, medical consumption cost, and health-related quality of life.
3.5. Secondary work productivity outcomes and EQ-VAS
Higher BSA was associated with more absence due to psoriasis, more work productivity impacted when present, a higher impact of psoriasis on daily functioning, and a lower overall health status according to the EQ-VAS ().
Table 5. Associations of BSA with other outcomes of work productivity and health-related quality of life.
3.6. Setting treatment goals and overall treatment satisfaction in the past year
Treatment goals between physician and respondent were discussed in 216 (43%) respondents, and not discussed in 202 (40%). In addition, 83 respondents (17%) reported ‘not applicable’ (). If treatment goals were not discussed, 91% did not find this problematic. Setting treatment goals largely did not differ by BSA categories ().
Table 6. Setting treatment goals and overall treatment satisfaction in the past year.
Respondents were most often somewhat (42%) or very (32%) satisfied with their treatment in the past year, with slightly higher levels of satisfaction for BSA >1% ().
4. Discussion
In this cross-sectional, online questionnaire study, higher severity of skin lesions in psoriasis as assessed by BSA was associated with higher overall work impairment due to psoriasis, higher medical consumption costs, and lower health-related quality of life.
Associations of psoriasis severity with work productivity or medical costs were studied before in studies in the US and Europe, in young adults from the Netherlands, in a registry-based study in Japan and in re-analyses of clinical trials (Citation7,Citation9,Citation26,Citation27) and were largely in line with our findings. Our study presented results adjusted for key potential confounders in an adult population. Furthermore, our study highlighted the importance of productivity impairment due to psoriasis, which has not been studied frequently in other cost studies in psoriasis (Citation28).
Complementary to prospective cohort studies in a clinical setting using measures of change (Citation14), we showed that a single timepoint measure of BSA also provides valuable information on patient-reported outcomes for a cutoff of 1% or 0% but not for a higher cutoff. Our cross-sectional approach with only one time-point is supported by a recent Delphi study suggesting absolute levels of the extent of lesions could also be used to assess treatment responses (Citation29). Our study suggests that BSA at a cutoff of 0-1% is a feasible severity indicator. Furthermore, our analyses combining BSA with DLQI support that, beyond BSA, health-related quality of life indicators might be stronger associated with psoriasis outcomes (Citation15,Citation25,Citation30). Lastly, in this cross-sectional study, 29% of the respondents had BSA 0-1% (‘clear’ or ‘near-clear’ skin) suggesting that this is a feasible treatment goal in contemporary psoriasis management.
Treatment goals are increasingly important in clinical practice, especially with more intensive systemic treatments. Therefore, finding only 43% of respondents reporting any discussion of treatment goals was lower than expected. Finding largely no difference across BSA categories aligns with previous studies indicating that patients with stable disease could still have active treatment goals (Citation31). Interestingly, if treatment goals were not discussed, 91% of respondents did not perceive this as problematic. This percentage is higher than expected, although we are not sure if this indicates true satisfaction with not setting goals. Psoriasis guidelines implement a stepwise increase in treatment intensity with a lack of disease control. The time from diagnosis to initiation of biologic treatments was on average 18 years in a Dutch cohort study between 2005 and 2015 (Citation32). Considering the negative impact of psoriasis lesions on relevant socio-economic outcomes and quality of life, future studies should consider determining what practices on setting treatment goals in psoriasis care are most optimal.
Treatment satisfaction also seemed largely favorable irrespective of BSA category, and was higher in our study than reported in a large US survey (Citation17). Finding high treatment satisfaction may be in line with previous findings of Dutch psoriasis patients using biologics reporting high medication satisfaction (Citation33).
Several methodological considerations should be mentioned. Strengths of our study include the modeling approach allowing to adjust for potential confounders, which is scarcely used in other studies. Furthermore, our study allowed assessing a substantial number of respondents in the working population in a short time using multiple validated instruments in a questionnaire without substantial drop-out. Regarding limitations, first we could only determine overall work impairment due to psoriasis in patients working for pay last week. Nevertheless, associations for secondary WPAI-derived outcomes were largely in line with our main findings. Moreover, employed/school-going respondents not included in the primary analysis seemed less healthy with slightly higher BSA levels. This may have underestimated our associations for overall work impairment due to psoriasis. Second, results suggested that our study included respondents with relatively severe psoriasis. The proportion of respondents using systemic medication was high (biologic use 44% versus <1% in a recent Dutch GP study (Citation9)), 44% had a history of psoriatic arthritis, and DLQI scores were lower in our study than in outpatients of a tertiary hospital in young adults (Citation9). Self-selection could have been present due to inclusion through an online panel, where the prevalence of psoriasis was estimated around ∼1% (unpublished data) as opposed to a recent estimate of 2.4% for the Netherlands (Citation5,Citation34). Selection after invitation was limited since drop-out was low and included respondents largely did not differ in age or sex from excluded respondents. Still, we included over 200 patients without concomitant systemic treatment, from a non-clinical sample, which supports the generalizability of our findings to psoriasis patients in the Netherlands. Third, we have not included psoriasis-specific healthcare use for medical consumption lacking in the costing manual (e.g., skin therapy), which may have underestimated associations with costs. Future studies would benefit from psoriasis-specific healthcare consumption, tissue involvement such as finger and toenails and other measures to get more precise estimates of diseases severity and a more thorough assessment of lifestyle including sleep disorders as sleep disorders additionally increase the risk of metabolic and psychiatric diseases in psoriatic patients who are already at increased risk of developing such disorders (Citation35).
To conclude, in this online questionnaire study in adults with self-reported psoriasis, a higher extent of skin lesions in psoriasis as assessed by BSA was associated with higher overall work impairment due to psoriasis, higher medical consumption costs, and lower health-related quality of life. Having few to no lesions was associated with better outcomes. Findings support the value of having few to no lesions in psoriasis management, both from a societal perspective for work productivity and medical consumption costs as well as an individual perspective for health-related quality of life.
What’s already known about this topic?
Psoriasis is a prevalent, chronic skin disease with a potential impact on work productivity, medical consumption costs and quality of life.
The extent of skin lesions is a central clinically useful indicator of disease severity, operationalized by total body surface area of a patient’s lesions (BSA).
The association of BSA with work impairment and medical consumption cost is not well known.
What does this study add?
We found associations for a higher extent of skin lesions with higher overall work impairment, higher medical consumption costs and lower health-related quality of life.
Findings support the benefit of having BSA 0-1%, or ‘clear or near-clear’ skin, in psoriasis for the best patient reported outcomes
We report medical consumption cost, and work productivity impairments for psoriasis patients in the Netherlands.
Supplemental Material
Download MS Word (105.3 KB)Acknowledgements
The authors are grateful to all study respondents, and to ‘Psoriasispatiënten Nederland’ and the involved patients for testing and improving our questionnaire. Support from Dynata in collecting study data is gratefully acknowledged.
Disclosure statement
TSL, RHB, KM, and HvB are employees of IQVIA, a human data science company, which received funds from Janssen-Cilag B.V. for the conduct of the study.
EJGMC, LL, and AM are employees of Janssen-Cilag B.V.
EMGJdJ has received research grants for the independent research fund of the department of dermatology of the Radboud university medical center Nijmegen, the Netherlands from AbbVie, BMS, Janssen Pharmaceutica, Leo Pharma, Lilly, Novartis, and UCB for research on psoriasis; has acted as consultant and/or paid speaker for and/or participated in research sponsored by companies that manufacture drugs used for the treatment of psoriasis or eczema including AbbVie, Boehringer-Ingelheim, Amgen, Almirall, Boehringer-Ingelheim, Celgene, Galapagos, Janssen Pharmaceutica, Lilly, Novartis, Leo Pharma, Sanofi and UCB. All funding is not personal but goes to EMGJdJ’s affiliated Institution.
Additional information
Funding
References
- Dubertret L, Mrowietz U, Ranki A, et al. European patient perspectives on the impact of psoriasis: the EUROPSO patient membership survey. Br J Dermatol. 2006;155(4):1–8. doi: 10.1111/j.1365-2133.2006.07405.x.
- Augustin M, Blome C, Paul C, et al. Quality of life and patient benefit following transition from methotrexate to ustekinumab in psoriasis. J Eur Acad Dermatol Venereol. 2017;31(2):294–303. doi: 10.1111/jdv.13823.
- Rapp SR, Feldman SR, Exum ML, et al. Psoriasis causes as much disability as other major medical diseases. J Am Acad Dermatol. 1999;41(3 Pt 1):401–407. doi: 10.1016/s0190-9622(99)70112-x.
- Parisi R, Iskandar IYK, Kontopantelis E, et al. National, regional, and worldwide epidemiology of psoriasis: systematic analysis and modelling study. BMJ. 2020;369:m1590. doi: 10.1136/bmj.m1590.
- AlQassimi S, AlBrashdi S, Galadari H, et al. Global burden of psoriasis - comparison of regional and global epidemiology, 1990 to 2017. Int J Dermatol. 2020;59(5):566–571. doi: 10.1111/ijd.14864.
- Brezinski EA, Dhillon JS, Armstrong AW. Economic burden of psoriasis in the United States: a systematic review. JAMA Dermatol. 2015;151(6):651–658. doi: 10.1001/jamadermatol.2014.3593.
- Villacorta R, Teeple A, Lee S, et al. A multinational assessment of work-related productivity loss and indirect costs from a survey of patients with psoriasis. Br J Dermatol. 2020;183(3):548–558. doi: 10.1111/bjd.18798.
- Armstrong AW, Schupp C, Wu J, et al. Quality of life and work productivity impairment among psoriasis patients: findings from the national psoriasis foundation survey data 2003-2011. PLOS One. 2012;7(12):e52935. doi: 10.1371/journal.pone.0052935.
- Bronckers I, van Geel MJ, van de Kerkhof PCM, et al. A cross-sectional study in young adults with psoriasis: potential determining factors in quality of life, life course and work productivity. J Dermatolog Treat. 2019;30(3):208–215. doi: 10.1080/09546634.2018.1506077.
- Korman NJ, Zhao Y, Pike J, et al. Relationship between psoriasis severity, clinical symptoms, quality of life and work productivity among patients in the USA. Clin Exp Dermatol. 2016;41(5):514–521. doi: 10.1111/ced.12841.
- Elmets CA, Korman NJ, Prater EF, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with topical therapy and alternative medicine modalities for psoriasis severity measures. J Am Acad Dermatol. 2021;84(2):432–470. doi: 10.1016/j.jaad.2020.07.087.
- (NVDV) NVvDeV. Richtlijn psoriasis. 2024. https://richtlijnendatabase.nl/richtlijn/psoriasis/startpagina_-_psoriasis2.html
- Armstrong AW, Siegel MP, Bagel J, et al. From the medical board of the national psoriasis foundation: treatment targets for plaque psoriasis. J Am Acad Dermatol. 2017;76(2):290–298. doi: 10.1016/j.jaad.2016.10.017.
- Bruins FM, Bronckers I, Groenewoud HMM, et al. Association between quality of life and improvement in psoriasis severity and extent in pediatric patients. JAMA Dermatol. 2020;156(1):72–78. doi: 10.1001/jamadermatol.2019.3717.
- Heydendael VM, de Borgie CA, Spuls PI, et al. The burden of psoriasis is not determined by disease severity only. J Investig Dermatol Symp Proc. 2004;9(2):131–135. doi: 10.1111/j.1087-0024.2004.09115.x.
- Salgado-Boquete L, Carrascosa JM, Llamas-Velasco M, et al. A new classification of the severity of psoriasis: what’s moderate psoriasis? Life. 2021;11(7):627. doi: 10.3390/life11070627.
- Armstrong AW, Robertson AD, Wu J, et al. Undertreatment, treatment trends, and treatment dissatisfaction among patients with psoriasis and psoriatic arthritis in the United States: findings from the national psoriasis foundation surveys, 2003-2011. JAMA Dermatol. 2013;149(10):1180–1185. doi: 10.1001/jamadermatol.2013.5264.
- Reilly MC, Zbrozek AS, Dukes EM. The validity and reproducibility of a work productivity and activity impairment instrument. Pharmacoeconomics. 1993;4(5):353–365. doi: 10.2165/00019053-199304050-00006.
- Noben CY, Evers SM, Nijhuis FJ, et al. Quality appraisal of generic self-reported instruments measuring health-related productivity changes: a systematic review. BMC Public Health. 2014;14(1):115. doi: 10.1186/1471-2458-14-115.
- iMTA. Manual iMTA Medical Cost Questionnaire (iMCQ). 2024. https://www.imta.nl/questionnaires/imcq/#:∼:text=The%20iMTA%20Medical%20Consumption%20Questionnaire,is%20therefore%20not%20disease%20specific
- Rabin R, de Charro F. EQ-5D: a measure of health status from the EuroQol group. Ann Med. 2001;33(5):337–343. doi: 10.3109/07853890109002087.
- Versteegh MM, Attema AE, Oppe M, et al. Time to tweak the TTO: results from a comparison of alternative specifications of the TTO. Eur J Health Econ. 2013;14(Suppl 1):S43–S51. doi: 10.1007/s10198-013-0507-y.
- Shikiar R, Bresnahan BW, Stone SP, et al. Validity and reliability of patient reported outcomes used in psoriasis: results from two randomized clinical trials. Health Qual Life Outcomes. 2003;1(1):53. doi: 10.1186/1477-7525-1-53.
- Yang Y, Brazier J, Longworth L. EQ-5D in skin conditions: an assessment of validity and responsiveness. Eur J Health Econ. 2015;16(9):927–939. doi: 10.1007/s10198-014-0638-9.
- Strober B, Ryan C, van de Kerkhof P, et al. Recategorization of psoriasis severity: delphi consensus from the international psoriasis council. J Am Acad Dermatol. 2020;82(1):117–122. doi: 10.1016/j.jaad.2019.08.026.
- Wu JJ, Lin CY, Goldblum O, et al. Efficacious psoriasis treatment improves patients’ work productivity. J Eur Acad Dermatol Venereol. 2020;34(10):e593–e596. doi: 10.1111/jdv.16457.
- Saeki H, Kanai Y, Murotani K, et al. Work productivity in real-life employed patients with plaque psoriasis: results from the ProLOGUE study. J Dermatol. 2022;49(10):970–978. doi: 10.1111/1346-8138.16517.
- Igarashi A, Yuasa A, Yonemoto N, et al. A systematic literature review of economic evaluations and cost studies of the treatment of psoriasis, atopic dermatitis, and chronic urticaria. Dermatol Ther. 2022;12(8):1729–1751. doi: 10.1007/s13555-022-00774-2.
- Belinchón Romero I, Dauden E, Ferrándiz Foraster C, et al. Therapeutic goals and treatment response evaluation in moderate to severe psoriasis: an experts opinion document. Ann Med. 2021;53(1):1727–1736. doi: 10.1080/07853890.2021.1986637.
- Gottlieb AB, Levin AA, Armstrong AW, et al. The international dermatology outcome measures group: formation of patient-centered outcome measures in dermatology. J Am Acad Dermatol. 2015;72(2):345–348. doi: 10.1016/j.jaad.2014.11.002.
- van Muijen ME, Atalay S, van Vugt LJ, et al. Unmet personal patient needs in psoriasis patients with low disease activity on adalimumab, etanercept or ustekinumab. Drugs Real World Outcomes. 2021;8(2):163–172. doi: 10.1007/s40801-021-00227-w.
- van den Reek J, Seyger MMB, van Lumig PPM, et al. The journey of adult psoriasis patients towards biologics: past and present – Results from the BioCAPTURE registry. J Eur Acad Dermatol Venereol. 2018;32(4):615–623. doi: 10.1111/jdv.14684.
- Driessen RJ, Bisschops LA, Adang EM, et al. The economic impact of high-need psoriasis in daily clinical practice before and after the introduction of biologics. Br J Dermatol. 2010;162(6):1324–1329. doi: 10.1111/j.1365-2133.2010.09693.x.
- CBS. Ruim 1,2 miljoen Nederlanders hebben eczeem of psoriasis. 2024. https://www.cbs.nl/nl-nl/nieuws/2015/46/ruim-1-2-miljoen-nederlanders-hebben-eczeem-of-psoriasis
- Nowowiejska J, Baran A, Flisiak I. Mutual relationship between sleep disorders, quality of life and psychosocial aspects in patients with psoriasis. Front Psychiatry. 2021;12:674460. doi: 10.3389/fpsyt.2021.674460.