patient preference on psoriasis treatment in a philippine ... · conjoint analysis (ca) is suited...

Patient preference on psoriasis treatment in a Philippine tertiary hospital: A conjoint analysis

Nikki G. Gonzales, MDa; Bryan Edgar K. Guevara, MDa, Lalaine R. Visitacion, MDa

Background: Psoriasis is a common and chronic papulosquamous skin disease leading to dissatisfaction and non-adherence to treatment among patients. Dermatologists should identify preferences of patients in choosing treatment options in order to optimize treatment satisfaction, adherence and outcome.

Objectives: To determine patients’ preferences for psoriasis treatments and analyze these preferences according to patients’ sociodemographic and socioeconomic profiles.

Methods: This was a cross-sectional study among adult patients with psoriasis seen at the Outpatient Department of a tertiary hospital, evaluating their preferences for psoriasis treatments based on outcome and process attributes using a self-administered questionnaire. A conjoint analysis determined the most preferred treatment combinations. The validity of correlation was assessed using Pearson’s R and Kendall’s tau.

Results: Among the 62 respondents, the most preferred outcome attribute for treatment was duration of benefit (RIS, 42.72) followed by probability of adverse effects (RIS, 31.29) and magnitude of benefits (RIS, 25.99). Among the process attributes, the frequency of treatment (RIS, 33.34) was regarded as the most preferred, followed by mode (RIS, 26.46), location (RIS, 20.89) and cost of treatment (RIS,19.31). A topical medication taken or applied thrice weekly with cost of less than Php 500, and consulation done at the clinic setting, was the preferred process treatment combination. There were no significant differences in RIS across different sociodemographic and socioeconomic groups.

Conclusion: The findings of this study can give dermatologists guidance on the choice of treatment characteristics for patients with psoriasis that is close to their preferences to ensure good compliance and better outcome.

INTRODUCTION

Psoriasis is a chronic, inflammatory, immune-mediated skin disease characterized by complex alterations in epidermal growth and differentiation and multiple

biochemical, immunologic, and vascular abnormalities.1,2

It affects around 1-3% of the world population, and around 1-2 million Filipinos.3,4 According to the Health Information System (HIS) of the Philippine Dermatological Society (PDS), psoriasis was among the top 10 reasons for consultation in dermatology institutions last 2011.5 Psoriasis was consistently the 2nd most commonly diagnosed disease in our institution from 2013 to 2015.6

Psoriasis significantly affects the patient’s quality of life, producing social stigma, pain, discomfort, physical disability and psychological distress. Because of its chronic and recurrent nature,7-8 the disease also places an economic burden to patients, using greater health care resources and significantly incurring greater health care costs compared with the general population.9

A wide array of treatment options for psoriasis is available depending on the severity of the disease. This includes topical

therapies, phototherapy, systemic medications and biologics. Although thesetreatments control the symptoms of psoriasis, there is no effective cure.10 Because of the chronic, recurrent nature of the disease, patients may become frustrated with the management and outcome of their therapies, affecting adherence and compliance to treatment.10 Worldwide, nonadherence rates are reported in 40% to 70% of patients with psoriasis.11

Compliance in health care is influenced by physician-patient relationship, physician’s recommendations and patient preferences.11 Patient preferences on treatment options generally depend on treatment benefits and adverse effects, as well as the location, duration and costs of treatment. In a study done by Seston et al.12 patients with psoriasis preferred attributes such as adverse effects, time to improvement, and time to relapse when choosing among the various treatment options. Furthermore, patients with psoriasis are willing to try variations of treatment to achieve improvement of their condition.12

Ideally, the best drug to prescribe is one with the highest efficacy and cost-effectiveness, and is associated with least adverse effects. Unfortunately, there is no single drug that has all of these properties. An understanding of patient preferences when it comes to treatment will help in deciding which management to prescribe and would lead to adherence and subsequent disease control.

Patient preference is the patient’s value for a specific component or attribute, either in absolute terms or in relation

a Department of Dermatology, Southern Philippines Medical Center, Bajada, Davao City, Philippines

Source of funding: noneConflict of interest: none Corresponding author: Bryan Edgar K. Guevara,MDEmail: [email protected]

J Phil Dermatol Soc • May 2017 • ISSN: 2094-201X 21

to another attribute.13 It can evaluate interventions that currently do not exist in the form of hypothetical treatments allowing evaluation before a medical plan or intervention is designed and developed. Preference methods are flexible and adaptable to practically any health-related question and thus uniquely suited to quantify the effect of treatment features on adherence, the tradeoffs between health outcomes and other treatment features, the risk-benefit tradeoffs, and monetary valuations related to treatment options.13

Conjoint analysis (CA) is suited for determining patient preferences on products or services. This program is widely used in the field of marketing research. It is a technique wherein sets of attribute combinations for a selected product or service are ranked by the subjects according to their preference.14-16 Patient preferences vary as a result from the clients’ or patients’ cognition and experience.17

In recent times, CA has been successfully used in measuring preferences for a diverse range of health applications. Studies using conjoint analysis have been done in cancer treatments, human immunodeficiency virus prevention, testing and treatment, dermatological services, asthma medications, genetic counselling, weight-loss programs, diabetes treatment and prevention, colorectal cancer screening, depression, and treatments for Alzheimer’s disease.16 A local study about the clients’ preferences on clinical laboratory using a conjoint analysis was done and revealed that customer service is paramount in the choice of a clinical laboratory.18

Studies investigating patient preferences in psoriasis treatment have only been done in developed countries,8,13 and to the best of our knowledge, there are no published reports of similar studies in the Philippines. Thus, it is important to do local studies on patient treatment preferences because the findings could be different among patients from developed and developing countries, and these may be due to sociodemographic and socioeconomic factors. A local study on patient preferences can guide dermatologists in selecting the optimum management that will improve patient compliance and satisfaction.

OBJECTIVES

The study aimed to determine and compare patient preferences for psoriasis treatments using a computer-based conjoint analysis.

This study specifically aimed to 1) determine patient preferences on treatment outcomes, treatment processes, their preferred combinations of attributes and levels, and 2) determine whether these preferences were significantly related to sociodemographic and socioeconomic status.

METHODS

Research DesignThis was a cross-sectional study among adult patients

with moderate to severe psoriasis, evaluating their preferences for psoriasis treatments in terms of outcome attributes

(probability, magnitude, and duration of benefit, as well as probability, severity, and reversibility of adverse effects) and process attributes (treatment location, frequency, duration, delivery method, and individual cost) using a self-administered questionnaire.

Relative importance score (RIS) ranging from 0-100 for each treatment attribute was calculated to assess its value using a computer-based conjoint analysis. The computer analysis program also generated a total utility score (TUS) ranging from 0-100 that determined the most preferred treatment combinations. The validity of correlation of RIS and TUS were assessed using Pearson’s and Kendall’s taucoefficient. The relationship of sociodemographic (age, sex, and marital status) and socioeconomic (income and employment) characteristics on preferences were also assessed.

Setting and participantsThe study was conducted at an outpatient clinic of a

tertiary hospital from September to November 2014. Patients aged 18 years-old and above clinically diagnosed with moderate to severe psoriasis according to Psoriasis Area and Severity Index (PASI) score were included in the study. A certificate of approval from the ethics board committee was obtained before study commencement. A written informed consent approved by the Hospital Research and Ethics Committee was obtained from all respondents.

VariablesIndependent variables include age, gender, civil status,

occupation, income and PASI scores.Dependent variables include the outcome attributes

(magnitude of benefits, duration of benefits and probability of adverse effects) and the process attributes (location of treatment, mode of treatment, frequency of treatment and cost of treatment).

Study phases (Data sources)The study consisted of two phases. Phase I included

the key informant interview (KII) of ten respondents to identify key attributes associated with psoriasis treatment. Most preferred attributes were then used in Phase II of this study. Phase II utilized a structured questionnaire composed of sociodemographic and socioeconomic profiles and hypothetical scenarios of treatment attributes. Using a conjoint analysis program, the utility estimates and relative importance scores (RIS) for each attribute and correlation measures of observed and estimated preferences were computed. Subgroup analyses of sociodemographic and socioeconomic profiles were performed.

Phase ITen key informants composed of five patients with

psoriasis, a university professor, a health care worker and three dermatologists were included in the Phase I. Key informant interview was performed to obtain information on knowledge on psoriasis treatment and to identify the important attributes of psoriasis treatment from people with diverse backgrounds

22 J Phil Dermatol Soc • May 2017 • ISSN: 2094-201X

and opinions through face to face interview. The KII was conducted in a private room where the respondents were asked key questions using an interview guide. Questions about their knowledge on psoriasis and its management were probed. The ten informants were also asked to rank different treatment attributes from the various treatment options (Figure 1).

The treatment attributes gathered from the key informants were divided into outcome attributes and process attributes. The KII was done to trim down the limitless possible choices of attributes to only the top three outcome attributes and top four process attributes.

The three outcome attributes included were the following: magnitude of benefit, duration of benefit and probability of adverse effects.

The four process attributes included the location, frequency, mode and cost of treatment.

The preferred attributes with their corresponding identified realistic levels were the basis for the hypothetical scenarios that were used in Phase II or study proper.

Phase IIThe Phase II study utilized a structured self-administered

questionnaire based on the results of the Phase I study. The questionnaire was explained thoroughly by the investigators

Figure 1. Flow chart summary of Phase I study.

to each respondent. The structured questionnaire contained the preferences of the respondents on psoriasis treatment that were presented as hypothetical treatment scenarios derived from the different levels of attributes previously identified using the KII (Phase I).

The sociodemographic profiles, socioeconomic profiles and PASI scores were determined (Figure 2).

The scenarios were designed using the commercially available conjoint analysis software. All attributes were separated into two groups (outcome and process) to avoid and lessen information overload to respondents. The respondents were instructed to rank the scenarios from 1 to 12. Rank 1 was assigned to the most preferred profile, 2 to the next preferred, and so on. No ranking was entered twice.

Outcome attributesThe first group (outcome) of attributes were composed of

the magnitude of benefit, duration of benefit and probability of adverse effects. The magnitude of benefit had two identified realistic levels: more than 50% reduction of psoriasis lesions and less than 50% reduction of psoriasis lesions. Duration of benefit had three identified realistic levels: about 3 months, 3 to 6 months, and more than 6 months. The probability of adverse effects had three identified realistic levels: none, about 50% and about 100%. A total of 18 (2x3x3) possible pairings or combinations were generated. Nine of the possible pairings/ cards were chosen by the conjoint analysis program as orthogonal design, three were set as holdouts, and the remaining six were set as simulation cards (Figure 3).

Only the design and holdout combinations were ranked by the respondents for simplicity. The simulation scores were based from holdout rankings, which were analyzed by the computer program to generate utility estimates.

The generated orthogonal design and holdout combinations were presented to the subjects for ranking. Holdout combinations or scenarios were judged by the subjects but were not used by the conjoint analysis to estimate utilities, instead these were used to check on the validity of the estimated utilities. Utility scores for simulation cards were

Figure 2. Flow chart of Phase II study.


Figure 3. Treatment outcome attributes with corresponding labels. There will be 18 possible combinations, and the software will generate 9 orthogonal designs, 3 holdouts and 6 simulation combinations.

computed using the utility estimates of each attribute level.

Process attributesThe second group (process) of attributes were composed

of the location of treatment as well as the mode, frequency and cost of treatment. Location of treatment included outpatient department (OPD) and home as realistic levels. Mode of treatment included phototherapy, oral therapy, and topical therapy as levels. Frequency of treatment included daily, once a week, and 3 times a week as levels. Cost of treatment included <Php500 , Php500-1000 , and >Php1000 as levels. A total of 54 (2x3x3x3) possible pairings or cards were generated for the process attributes. Nine of the possible combinations were chosen by conjoint analysis program as orthogonal design and four were set as holdouts and the remaining combinations were set as simulation cards (Figure 4).

Study SizeAccording to Orme (2010), for investigational work

and developing hypotheses about a market, between 30 to 60 respondents is sufficient,19 while Walpole et al. (2012) suggested that a sample size of 30 is an acceptable sample size for conjoint studies.20 Hence, Phase II of this study was conducted with more than 60 respondents.

Statistical analysisThis study used a full profile conjoint analysis using

fractional factorial design which presented a suitable fraction of all possible combinations of the different attributes levels. Frequency distribution, percentages, means and standard deviations were utilized to describe the respondents’ sociodemographic and socioeconomic profiles.

All data that were gathered in this study were encoded directly to SPSS or Statiscal Package for the Social Sciences, which was developed by IBM with an initial release in 1968. Using the conjoint analysis command in the program, the utility

estimates and standard errors for each attribute level and RIS, correlation measures Pearson’s R and Kendall’s Tau, TUS for the design, holdout, and simulation cards were computed. Subgroup analysis was performed by sociodemographic and socioeconomic profiles.

Utility estimates were used to compare each attribute level for both process and outcome attributes. RIS for each attribute was calculated to find out which of the different attributes is most important in making a treatment preference. TUS were used to find out which treatment combinations for both outcome and process attributes were most desired by patients.

Pearson’s R and Kendall’s tau coefficients were calculated to provide measures of the correlation between the observed and estimated preferences. Analysis using Kendall’s tau was used for the holdout profiles. Simulations of the different attributes and levels were performed to predict preferences that were not included in the questionnaire and were not rated by the subjects. A p-value of ≤ 0.05 was considered significant.

RESULTS

Phase IBased on the ten respondents from key informant

interview (KII), the initial eleven identified attributes were narrowed down to seven based on the top choices of the key informants. Three preferred outcome attributes (magnitude of benefits, duration of benefits and probability of adverse effects) and four process attributes (location of treatment, frequency of treatment, mode of treatment and cost of treatment) were included in Phase II.

Phase II Sixty-two patients were included in Phase II. All

respondents completed the questionnaire. The baseline

Figure 4. Treatment process with corresponding labels. There will be 54 possible combinations, and the software will generate nine orthogonal designs, four holdouts and 41 simulation combinations.


characteristics (age, sex, civil status, occupation and monthly income) of the respondents are presented in Table 1.

of less Php 500 had the highest utility score (8.27). While the treatment combination of phototherapy given once a week at home with a weekly cost of more than Php 1000 had the lowest utility (1.75) (Table 3).

The RIS and correlation tables for outcome and process attributes are presented in Tables 4 and 5. Among the given outcome attributes, the duration of benefit (RIS= 42.72) was regarded as the most preferred, followed by probability of adverse effects (RIS= 31.29) and magnitude of benefits (RIS= 25.99) (Table 4). Pearson’s R and Kendall’s tau values were less than 0.05, which indicates the consistent correlation of the design, holdout and simulation combinations. Kendall’s tau for holdouts value was more than 0.05, which indicates the validity of the utility estimates.

Among the process attributes, frequency of treatment (RIS=33.34) was regarded as the most preferred process attribute, followed by mode of treatment (RIS=26.46), location of treatment (RIS=20.89) and cost of treatment (RIS=19.31) (Table 5). Pearson’s R and Kendall’s tau values were less than 0.05, which indicates the consistent correlation of the design, holdout and simulation combinations. Kendall’s tau for holdouts value was more than 0.05, which indicates the validity of the utility estimates.

Results of the study revealed that <50% magnitude of benefit had higher utility estimate over >50% of benefit. Duration of benefit at >6 months was preferred over the 3 to 6 months and <3 months duration. The probability of no adverse effects was preferred over those with >50% and >100% probability of adverse effects (Table 6 and Figure 5)

Among the process attributes, treatment at the OPD had a positive utility estimate versus home treatment. Topical therapy had a higher utility estimate than oral therapy and phototherapy. For the frequency of treatment, treatment done thrice a week had higher utility estimates than daily and once weekly treatments. A weekly cost of treatment at less Php 500 had lower negative utility estimates than more expensive treatments (Table 7 and Figure 6).

There were no significant differences in relative importance scores (RIS) among the respondents when grouped according to sex, age groups, civil status, occupation, PASI scoring, and monthly income (Table 8).

DISCUSSION

The most preferred treatment outcome attribute and process attributes were the duration of benefit (> 6months) and frequency of treatment (thrice weekly), respectively.

There were no significant differences in RIS for the outcome and process attributes among the different sociodemographic and socioeconomic groups.

Our results showed that a treatment outcome combination of >50% magnitude of benefit with 6 months onwards duration of benefits and with no chance of having any adverse effects had the highest utility score. The treatment combination of >50% magnitude of benefits with less than 3 months duration of benefits and with 100% probability of adverse effects was the least preferred outcome

There were 34 (54.8%) female respondents and 28 (45.2%) male respondents in the study. The mean age for the study population was 35 ± 7 years old. About two-thirds of the respondents were married. Thirty-seven (59.7%) of the respondents were employed. Fifty-two (83.9%) of the respondents have a monthly income of less than Php 10,000. There were 49(79%) study respondents who had PASI scores ranging from 10-19, 12 (19.4%) with PASI scores ranging from 20-29, and one (1.6%) with PASI of 30-39.

Treatment scenarios or combinations for both outcome and process groups with their corresponding total utility scores were presented in Tables 2 and 3. Our results showed that a treatment combination of >50% magnitude of benefit with six months onwards duration of benefits and with no chance of having any adverse effects had the highest utility score (6.23). The treatment combination of >50% magnitude of benefits with less than three months duration of benefits and with 100% probability of adverse effects had the lowest (3.62) utility score (Table 2).

The treatment combination of topical medications given thrice a week at the outpatient department with a weekly cost

Table 1. Sociodemographic and socioeconomic profiles of the respondents.

%N

GenderMaleFemale

Age (Mean + SD = 35 + 7)18-35 36-49 50-6465 and above

Civil statusMarriedSingle

OccupationEmployedUnemployed

PASI Score (Mean + SD = 15 + 5.1)10-1920-2930-39

Monthly income (Php)<10,00010,000-25,000>25,000

2834

2118176

4220

3725

49121

5246

45.254.8

33.929

27.49.7

67.732.3

59.740.3

7919.41.6

83.96.59.7

CHARACTERISTIC

PASI, Psoriasis area and severity index


combination. The treatment process combination of topical medications applied thrice weekly with a weekly cost of less than Php 500, and outpatient clinic consultations was the most preferred scenario, while the treatment process combination of phototherapy given once a week at home with a weekly cost of more than Php 1000 had the lowest utility. There was an inverse relationship between cost and treatment utility, with higher cost of treatment corresponding to lower treatment utility.

This study revealed that the preferred treatment outcome attribute of our respondentsis the duration of therapeutic effects. This differed from results of previous researches conducted among patients with psoriasis.8,13 In a study by Schaarschmidt et al (2011),8 treatment location was considered the most significant attribute, while conjoint studies done by Kromer et al. (2015)13 and Seston et al. (2007)12 showed that patients preferred treatments with the least adverse effects.

Patients with psoriasis in this study regarded frequency of treatment and duration of the benefit of psoriasis treatment as the most important attributes. Since psoriasis is a chronic, recurrent disease,1,2 patients would likely prefer treatment options that can be used in prolonged periods with maximal efficacy and minimal side effects. Respondents gave more importance to frequency of treatment over mode, location

and cost of treatment. This may be because most of the respondents were middle-aged adults who were employed and likely prefer a moderately frequent treatment process that can provide maximal efficacy, such as thrice a week regimen compared to a daily or once a week frequency of treatment.

With regards to the combination of process attributes, majority of the respondents preferred a topical treatment option, ideally given thrice weekly at an outpatient setting. These findings may be because 52% of study respondents had a monthly income of less than Php 10,000, or belong to the lower middle-income families. The convenience of local and topical therapy explains the high acceptance level of this mode of treatment which patients may have perceived cheaper than the others. The preference for thrice weekly treatments may be explained by the fact that majority of the patients are working so that allotted time for treatments must be less frequent but the interval between treatments must not also be prolonged so that the healing process will not be affected. The patients’ preference for the treatments to be done at the outpatient setting connotes their need for guidance and follow-up check-up by their doctors during the course of the treatment process.

Our results contrasted with the findings of a conjoint analysis done by Schaarschmidt et al. (2011),8 which revealed that German patients with psoriasis regarded treatment

a TUS, total utility score

Table 2. Treatment combinations (outcome) with their corresponding TUS.

DURATION OF BENEFITMAGNITUDE OF BENEFIT

Design

Holdout

Simulation

<50%

<50%

<50%

<50%

>50%

>50%

>50%

>50%

>50%

>50%

>50%

>50%

<50%

>50%

<50%

>50%

<50%

<50%

<3 months

<3 months

3 to 6 months

3 to 6 months

3 to 6 months

>6 months

3 to 6 months

>6 months

3 to 6 months

<3 months

>6 months

<3 months

<3 months

>6 months

3 to 6 months

<3 months

>6 months

>6 months

CHARACTERISTIC TUSAPROBABILITY OF ADVERSE EFFECTS

None

About 100%

About 50%

None

None

None

About 100%

About 100%

About 50%

About 100%

None

None

About 50%

About 50%

About 100%

About 50%

About 50%

About 100%

4.97

4.04

5.13

5.60

5.18

6.23

4.25

4.88

4.72

3.62

5.81

4.55

4.50

5.35

4.67

4.08

5.77

5.30


TUS, total utility score

Table 3. Treatment combinations (process) with their corresponding TUS.

MODE OF TREATMENT

LOCATION OF TREATMENT

Design

Holdout

Simulation

HomeOPDOPDOPD

HomeHomeHomeHomeHome

HomeOPDOPD

Home

HomeHomeHomeOPDOPDOPD

HomeHomeHomeHomeOPD

HomeOPDOPD

HomeOPD

HomeOPD OPD OPD OPD

HomeOPD

HomeHomeHomeHomeOPD OPD OPD OPD OPD

HomeOPDOPD

HomeOPD OPD OPD

HomeHome

OralTopical

PhototherapyOral

PhototherapyTopicalTopical

PhototherapyOral

TopicalOral

TopicalTopical

TopicalTopical

OralOral

PhototherapyOral

TopicalOral

PhototherapyPhototherapyPhototherapyPhototherapy

TopicalOral

PhototherapyTopical

PhototherapyPhototherapy

OralOral

PhototherapyPhototherapyPhototherapy

TopicalOral

PhototherapyOral

TopicalPhototherapy

OralTopical

PhototherapyTopical

OralTopical

OralTopical

PhototherapyTopical

OralOral

TYPECOST OF

TREATMENT(Php)

FREQUENCY OF TREATMENT

3x a week1x a week3x a week

DailyDaily

3x a weekDaily

1x a week1x a week


Daily

1x a week3x a week

Daily3x a week3x a week3x a week

Daily3x a week3x a week3x a week1x a week1x a week

Daily1x a week1x a week

DailyDailyDailyDaily

3x a weekDailyDailyDaily

1x a week1x a week3x a week3x a week3x a week1x a week

Daily3x a week3x a week3x a week1x a week

DailyDaily


Daily1x a week

500-1000500-1000

<500>1000

500-1000>1000<5000>1000<500

<500<500<500

>1000

500-1000<500

500-1000<500

>1000>1000

500-1000>1000<500

500-1000500-1000500-1000

>1000>1000<500

500-1000<500<500<500

500-1000500-1000

>1000>1000>1000

500-1000>1000<500<500

>1000500-1000500-1000500-1000500-1000500-1000

<500<500

>1000<500

>1000>1000>1000

TUS

5.775.276.945.833.955.405.961.754.12

4.425.655.954.61

3.756.754.987.975.596.625.285.105.424.743.952.426.134.303.106.814.636.157.187.305.483.284.803.083.454.076.458.273.276.517.606.276.074.977.485.666.924.624.604.312.77


Figure 5. Illustration and comparison of the utilities and RIS: treatment outcome. RIS, relative importance score

Table 4. Correlation between outcome attributes and RIS.

RISa

Magnitude of benefitDuration of benefit

Probability of adverse effects

Pearson’s R coefficient = 0.721, p-value =0.007Kendall’s tau = 0.800, p-value = 0.003Kendall’s tau for holdouts = 0.003, p-value = 0.301

25.99742.71631.286

OUTCOME ATTRIBUTE

a RIS, relative importance scores

RIS, relative importance scores

Table 5. Correlation between process attributes and RIS.

RIS

Location of treatmentMode of treatmentFrequency of treatmentCost of treatment

Pearson’s R coefficient = 0.993, p-value = 0.000Kendall’s tau = 0.889, p-value = 0.000Kendall’s tau for holdouts = 0.006, p-value = 0.875

20.88726.46333.34319.306

PROCESS ATTRIBUTE

Table 6. Overall utility estimate of outcome attributes.

STD. ERRORUTILITY ESTIMATE

Magnitude of benefits<50%>50%

Duration of treatment<3 months3 to 6 months>6 months

Probability of adverse effectsNoneAbout 50%About 100%

Constant

-0.418-0.836

0.6331.2651.898

-0.465-0.930-1.395

5.216

0.8181.637

0.5671.1341.701

0.4380.876

1.3144

1.422

OUTCOME ATTRIBUTES

Table 7. Overall utility estimate of process attributes.

STD. ERRORUTILITY ESTIMATE

Location of treatmentHomeOPD

Mode of treatmentTopicalOralPhototherapy

Frequency of treatmentDaily3x a week1x a week

Cost of treatment (Php)<500500 to 1000>1000Constant

-0.7620.762

0.5430.242-0.785

0.2471.038-1.285

-0.675-1.349-2.0246.603

0.1300.130

0.1740.1740.174

0.1740.1740.174

0.1500.3010.4510.328

OUTCOME ATTRIBUTES


location as the most important attribute whereas psoriasis patients in our study were not specifically concerned about treatment location. They concluded in the earlier study that the availability and popularity of local therapy in combination with UV light exposure in European countries predisposed most patients to highly prefer treatments performed in an inpatient or day hospital setting. In the Philippine setting, because phototherapy and systemic therapies require frequent laboratory workup and clinic visits, they are thus less preferred because of interference with work and other activities.

Although not statistically significant, there were some small differences in patient preference according to age, gender, civil status and socioeconomic status. Older respondents seemed to be more concerned with the duration of treatment benefit as compared to younger patients, probably because the former experienced a longer duration of the disease and have other co-morbid illnesses. Respondents who were single and employed favored a longer duration of therapeutic benefits more than the other outcome and process attributes presented. In addition, the magnitude and duration of benefits as well as the frequency of treatment mattered

more among the employed respondents compared to those who were not working. These findings weren’t surprising since psoriasis has been shown to substantially impair productivity.21-24 Respondents from low income families were more concerned about cost-effectiveness of the treatment as reflected by the higher preference values assigned to cost of treatment, frequency of treatment and the magnitude of the benefit of the treatment. Male patients seemed to highlight the magnitude of benefits while female patients were more concerned about the frequency of treatment. Male respondents favor magnitude of benefit of treatment, as also seen in German patients.8 This finding was interesting since women usually put more emphasis on appearance, and suffer more mentally than men.24,25

Strengths, limitation and recommendationTo the best of our knowledge, this is the first study on

patient preferences on psoriasis treatment in the Philippines. The study rendered valuable findings that will guide dermatologists in selecting the optimum management that will increase patient compliance and satisfaction.

PASI. Psoriasis area and severity indexStatistical test: ANOVA

Table 8. Treatment combinations (process) with their corresponding TUS.

DURATIONS OF BENEFITS

CHARACTERISTIC

SexFemaleMale

Age18-3536-4950-6465 and above

Civil statusMarriedSingle

OccupationEmployedUnemployed

PASI ScorePASI 10 -19PASI 20 -29PASI 30 - 39PASI 40 above

Monthly income (Php)<1000010,000-25000>25,000

25.3527.56

24.3029.5624.5027.90

25.6725.34

27.0024.10

27.0926.4023.1024.50

27.6021.7025.40

41.6742.87

39.8040.5043.0142.00

40.9842.76

45.3040.60

44.0142.1045.8042.90

43.2146.1244.09

MAGNATITUDE OF BENEFITS

LOCATION OF TREATMENT

20.6521.35

21.0020.7619.8921.00

22.3120.56

20.8021.06

23.4020.9019.4021.90

22.1019.8020.76

P-VALUE

OUTCOME ATTRIBUTES

PROBABILITY OF ADVERSE

EFFECTS

32.4531.68

29.0833.2132.0033.56

31.9033.10

32.9033.10

32.0935.7033.8029.80

31.3033.2032.09

MODE OF TREATMENT

FREQUENCY OF TREATMENT

COST OF TREATMENT

24.6726.89

27.1228.9023.4026.00

23.9825.00

25.8727.80

23.1026.9027.0123.86

25.8928.1023.01

35.4532.89

34.3332.1031.0933.00

33.0033.09

35.1033.40

35.9034.2139.7030.80

38.0133.0034.09

18.4520.10

19.8721.3420.1220.90

19.8721.30

20.1021.40

17.9021.7020.1019.09

23.1021.9020.12

PROCESS ATTRIBUTES

0.87

0.68

0.32

0.35

0.65

0.53


This study was conducted in a single center and only included patients with moderate to severe psoriasis treated in a local tertiary hospital. These findings may not be applicable to patients with milder or more severe disease. We did not investigate other factors that may impact patient preference such as disease duration, previous treatment experience, choice of physicians, and comorbidities. There may also be sampling bias because we only included patients seen in the outpatient, so these patients may already have preference for outpatient treatment. In addition, some medications such as the injectable biologicswere not included in the study.

We suggest that future studies will involve multiple centers, so as to increase sample size and have a more diverse patient population. We may also add more attributes that are known to impact the disease. A larger study investigating more attributes will also allow further investigation on the relationship of patient preferences to socioeconomic and sociodemographic factors since the differences we observed were not significant.

The knowledge of treatment preferences of psoriatic patients in our local setting obtained from this study together with expertise in evidence-based medical management of psoriasis will guide dermatologists in prescribing treatments that are likely to be preferred by patients. This will improve patient compliance and satisfaction, leading to better disease control and improving the quality of life of patients.

Figure 6. Illustration and comparison of the utilities and RIS: treatment process. RIS, relative importance score

CONCLUSION

The duration of benefit was the most preferred outcome attribute while the most preferred process attribute was frequency of treatment. There were no significant differences in RIS across different sociodemographic and socioeconomic groups. A treatment with an outcome of >50% magnitude of benefit with more 6 months duration of benefits and with no chance of having any adverse effects was most preferred by the patients. The treatment process combination of topical medications given thrice weekly with a weekly cost of less than Php 500, with consultations at the outpatient clinic was most preferred.

At present, there are no anti-psoriatic treatments that can fit into the chosen preferences by the respondents. However, the findings of this study can give the dermatologists guidance on the choice of treatment characteristics for patients with psoriasis to ensure good compliance and better outcome.

ACKNOWLEDGEMENTS

The authors would like to thank Dr. Maria Vinna N. Crisostomo and Dr. Mara Therese P. Evangelista for editing this paper.


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patient preference on psoriasis treatment in a philippine ... · conjoint analysis (ca) is suited...

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