Determinants of compliance with medication in ...

Patient Education and Counseling 36 (1999) 57–64

Determinants of compliance with medication in patients with rheumatoid arthritis: the importance of self-efficacy expectations b, a ,b c a ,c c Herman Brus *, Martin van de Laar , Erik Taal , Johannes Rasker , Oene Wiegman a

Rheumatology Twente, Department of Rheumatology Twenteborg Ziekenhuis, Almelo, The Netherlands Department of Rheumatology, Medisch Spectrum Twente, PO Box 50.000, 7500 KA Enschede, The Netherlands c Department of Applied Communication Sciences, Faculty of Philosophy and Social Sciences, University Twente, Enschede, The Netherlands b

Received 5 September 1997; received in revised form 20 April 1998; accepted 5 May 1998

Abstract In this study we examine which factors are related to compliance with medication in patients suffering from rheumatoid arthritis (RA). Patients: persons suffering recently developed, active RA, who cooperated in a randomized study on the effect of patient education. We analyzed the relation between adherence to Sulphasalazine therapy and personal factors, environmental influences, demographic factors, disease-related factors, and barriers to compliance. Moreover, a logistical regression analysis was performed on these factors, considering > 80% a high compliance, both with compliance as dependent factor. Only self-efficacy correlated with compliance (r 5 0.58; P , 0.001). The logistical regression analysis identified self-efficacy as the only factor determining > 80% adherence (P 5 0.01). Self-efficacy regarding the use of prescribed medication is related to compliance with this treatment. Further study is needed to determine the test characteristics of self-efficacy as a predictor for compliance with medication.  1999 Elsevier Science Ireland Ltd Keywords: Compliance; Self-efficacy; Rheumatoid arthritis; Patient education

1. Introduction Rheumatoid arthritis (RA) is a chronic disease that is characterized by inflammation of joints. The inflammation is reversible but may lead to irreversible joint damage. Treatment for RA is not curative,

*Corresponding author. Tel.: 1 31 534 872450; fax: 1 31 534 873106.

but improvement and remissions may be achieved [1–5]. The use of disease-modifying antirheumatic drugs (DMARDs) is particularly important because they have the potential to reduce and prevent joint damage and preserve joint integrity and function [1]. Nonsteroidal antiinflammatory drugs (NSAIDs) are used to relieve pain [3]. Other frequently prescribed treatments are physical exercise and ergonomic measures [4,5]. The effects of the treatments prescribed depend on the efficacy as well as on the compliance of the patients. Compliance, or adher-

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H. Brus et al. / Patient Education and Counseling 36 (1999) 57 – 64

ence, has been defined as ‘‘the extent to which a person’s behavior coincides with the medical or health advice’’ [6]. It refers to specific recommendations, such as taking a particular drug as prescribed. In the few studies dealing with adherence to DMARD therapy in clinical practice, compliance is estimated as 58–61% (patients considered compliant) or 84% (medication actually taken) [7]. Estimates of compliance with NSAID therapy range from 63 to 78% (patients considered compliant) or from 58 to 73% (medication actually taken) [7]. Studies on adherence to prescriptions of physical exercise and ergonomic measures indicate suboptimal compliance [7]. Haynes et al. have identified over 200 factors that have been studied in relationship to compliance [8]. The social learning theory by Bandura can help to understand the driving forces of human behavior [9]. Patient education in arthritis is commonly based on its principles [9–15]. The theory contends that human functioning involves a continuous interaction between behavior, personal factors, and external environment, a phenomenon that is called ‘reciprocal determinism’ [9,11]. An individual’s behavior is motivated and regulated by personal standards and by the evaluation of the reactions one’s own actions excite. The personal factors, self-efficacy expectation (briefly, self-efficacy) and outcome expectation, are regarded as important determinants of behavior. The first refers to the belief in one’s capabilities and opportunities to execute the behavior in order to produce a desired outcome, the second to one’s assessment of the chance that a certain behavior will have a beneficial effect. Moreover, positive or negative ideas of the social environment regarding a certain behavior and the presence or absence of help by its effectuation, are supposed to have an influence on the actual execution of this behavior. A model of health behavior adapted from the social learning theory, combining it with theorems of other theories [9,17,18], is described by Seydel et al. [16]. It illustrates how personal factors and the influences of the social environment may determine the behavior of a person. ‘External variables’ are assumed to affect behavior indirectly by influencing the outcome expectation, the self-efficacy or the

social environment. In the present study, diseaserelated factors and therapy are regarded as external variables. In the model, perceived barriers can prevent the intended behavior. Studies on the factors that determine compliance with medication among RA patients are scarce [7,19–25]. Lee and Tan found demographic factors to be poor predictors for the compliance with NSAIDs [20]. Deyo et al. found a weak correlation between compliance and the complexity of the regimen [21]. Studies by Capell et al. and by Lorish et al. indicate that patients tend to stop their medication when they experience side effects [22,23]. Ferguson found that non-compliance was related to a lack of belief in benefit [24]. Daltroy emphasized the role of the physician in patient compliance [25]. To the best of our knowledge the study of Beck et al. is the only one that examines whether selfefficacy or outcome expectations are related to adherence with advised medication in RA patients [26]. They studied the contribution of several factors to compliance with the prescription of an NSAID (salicylate) among 63 RA patients. Patients with serum levels of salicylate below 15 mg / dl were considered non-compliant. By means of a previous determination of the serum level, the self-efficacy expectation regarding termination of therapy and the self-efficacy regarding appointment keeping, a discriminant equation could be constructed that predicted 75% of non-compliers. Self-efficacy regarding taking salicylate medication on a regular basis, however, did not contribute to the correct prediction of compliance. Recently we performed a randomized controlled assessor-blinded trial among RA patients, on the effect of patient education. We found a high compliance with DMARD therapy in both study groups, but no additional effect of patient education on the compliance was found [27]. In the present study we examine, in the same population, the relation between compliance with DMARD medication (sulphasalazine) and: self-efficacy expectations and outcome expectations regarding the use of DMARD medication, perceived influences of the social environment, relevant demographic factors, relevant disease-related factors, and perceived barriers for being compliant.


2. Methods

2.1. Patients Consecutive patients with active RA according to the ACR criteria [28], diagnosed no longer than 3 years before the start of the study were selected by their rheumatologists during a visit at our out-patient clinic. Active disease was defined by the presence of all of the following; an erythrocyte sedimentation rate (ESR) greater than 28 mm / 1st hour; six or more painful joints; and three or more swollen joints. Patients who had used any DMARD other than hydroxychloroquine were excluded.

2.2. Study design The study design was a randomized, controlled, assessor-blinded, clinical trial. We intended to follow the patients during 1 year. To prevent patient bias, patients were first allocated at random to the experimental or control group and then asked to give informed consent for the group to which they were assigned, according to Zelen [27,29,30]. The experimental group attended six patient education meetings. The members of the control group received a brochure on RA and its basic treatment. All patients received regular treatment by their rheumatologist according to a sulphasalazine protocol. This protocol lays down that sulphasalazine 500 mg enteric coated tablets are prescribed, starting with one tablet a day, increasing the dose every week with one tablet a day up to a dose of four tablets. In individual patients, the dose could be increased to six tablets daily or reduced as much as deemed necessary, at the discretion of the attending physician. In case of lack of effect or toxicity therapy could be stopped also at the discretion of the patients’ own rheumatologist. All patients obtained sulphasalazine from their regular pharmacists.

2.3. Measures All variables were obtained by one assessor, who was blinded for the group to which the patients had been allocated. Age, gender and the level of formal education were determined. The level of formal

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education was scored in a range from 1 to 9, where 1 is the lowest level and 9 the highest level possible. At baseline the following health status assessments were performed; the pain scale of the Dutch Arthritis Impact Measurement Scales (Dutch-AIMS; a Dutch version of the AIMS) [31,32]. This scale consists of a series of questions about pain. The score ranges from 0 to 10, where 0 represents no pain and 10 maximal pain. Functional disability was measured by a Dutch version of the Health Assessment Questionnaire (M-HAQ) [14,33]. It yields a score, that ranges from 1 to 4, where 1 represents good physical function and 4 poor physical function. The disease activity was measured by a disease activity score (DAS) [34,35]. This is a function of one laboratory measure (the erythrocyte sedimentation rate (ESR; 0–140 mm / 1st hour)), and two clinical measures (the joint tenderness score according to Ritchie (0– 78) and the number of swollen joints (0–52)). The score of the DAS ranges from 0 to 10, where 0 represents a low and 10 a high disease activity. Compliance with sulphasalazine therapy was measured in the period 0–3 months and in the period 3–6 months after the start of the study. Self-efficacy and outcome expectations regarding this therapy, perceived influences of the environment and perceived barriers to compliance with sulphasalazine treatment were assessed at baseline and 3 months after the beginning of the study. Compliance with sulphasalazine was measured by means of a pillcounting procedure. Medical and pharmacy records were the source of data on the dosage prescribed and dosage obtained. For each evaluation, patients brought any unused medication to the assessor. Any remaining sulphasalazine tablets were counted. We defined compliance as the number of tablets taken divided by the number of tablets prescribed, expressed as a percentage. In this study compliance > 80% is considered a high compliance rate, compliance , 80% a low compliance rate. The following measurements were performed at 3 months. The self-efficacy expectation regarding the use of DMARD therapy, exactly according to the prescription of the physician was examined by one question, and the outcome expectation by assessing the mean score of two questions (one about expected improvement of the disease activity and another

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about expected limitation of destruction in the joints). Items could be answered on a 5-point scale, scores ranging from disagree totally ( 5 1) to agree totally ( 5 5), where 5 represents the highest selfefficacy possible, respectively the highest outcome expectation possible. Influence from the environment regarding the use of sulphasalazine was measured as the mean score of two questions (one asking about the attitude of family and friends towards the use of the medication by the patient and one about the support from family and friends in taking the medication), to be answered and scored in the same way as the above questions, where 5 represents the highest level of influence possible. Barriers for taking sulphasalazine tablets, as perceived by the patients, were measured in questionnaires as the mean score of four questions (being afraid of adverse reactions, doubts about the exact prescription, forgetfulness, the use of many other medications simultaneously), that could be answered on a 5-point scale, scores varying from disagree totally ( 5 1) to agree totally ( 5 5), where 5 represents the highest level of perceived barriers possible.

2.4. Statistical analysis Baseline characteristics of experimental group and control group were compared. The Wilcoxon twosample test was used for the comparisons of groups. The sex distributions were compared with the x 2 test. The internal consistencies of the questions regarding outcome expectations, those pertaining to the perceived influence of the social environment, and those pertaining to perceived barriers were assessed by determining the Cronbach’s a. Correlation coefficients according to Pearson were calculated for the compliance in the period between 3 and 6 months, and the other parameters measured at 3 months. Comparison of the baseline characteristics was made between patients to whom sulphasalazine was prescribed during the period between 3 and 6 months and the other patients. We applied a stepwise logistic regression analysis on the compliance and the variables measured at 3 months, with the adherence to sulphasalazine treatment as the dependent parameter. Since the data were obtained from a trial, the study condition was entered as first variable in these analyses. In the logistic regression analysis a

cut-off point of 80% was used, where a compliance rate of at least 80% was considered as compliant. Comparison of the baseline characteristics was made between the patients analysed in the logistical regression analysis and those not analysed.

3. Results Sixty-five patients were selected. Thirty-two were allocated to the experimental group and 33 to the control group. Three patients in the experimental group and two in the control group would not give informed consent. Four patients from the experimental group and one from the control group refused to attend all assessments during one year, and could not be incorporated in the analyses. Demographics and baseline scores of pain scale of the Dutch-AIMS, the M-HAQ and DAS of the remaining patients are shown in Table 1. In the control group there were more female patients. Compliance with sulphasalazine therapy in the period 0–3 months after baseline was 91% (S.D. 5 12) in the educated group and 87% (S.D. 5 22) in the control group (difference not significant). Sulphasalazine therapy was still prescribed to 47 patients (20 experimental, 27 control) in the period 3–6 months after baseline. The compliance with sulphasalazine therapy was 82% (S.D. 5 22) and 82% (S.D. 5 28) in the respective groups (difference not significant) [27]. Cronbach’s a for the two questions about outcome expectation was 0.77 (n 5 54). That of the four questions about barriers was 0.74 (n 5 46) and that Table 1 Demographic and baseline characteristics (mean [standard deviation])

Sex* Age (years) Education level (1–9) Pain AIMS (0–10) M-HAQ (1–4) DAS (0–10)

Experimental (n 5 25)

Control (n 5 30)

23 female (92%) 59.0 [15.0] 3.0 [1.7] 6.6 [1.8] m 51 1.7 [0.7] m 51 3.8 [0.9]

21 female (70%) 58.7 [9.2] 2.4 [1.4] 6.0 [1.9] m 51 1.5 [0.5] m 51 3.5 [0.7]

Pain AIMS, pain scale of Dutch Arthritis Impact Measurement Scales; M-HAQ, Health Assessment Questionnaire; DAS, Disease Activity Score. m, number of patients with missing data. *P , 0.05.


of the two questions about the perceived influence of the social environment was 0.52 (n 5 46). Because of the low internal consistency of the two questions assessing the influence of the social environment, these are treated as two separate variables: perceived attitude and perceived support of the social environment. The mean scores on self-efficacy and outcome expectations, as well as perceived influences from the social environment and perceived barriers regarding the use of sulphasalazine medication at 3 months are given in Table 2. There were no differences between groups. We did not find statistically significant differences in the baseline characteristics, between the 47 patients to whom sulphasalazine was still prescribed and the other eight patients. The correlation coefficients between the compliance with sulphasalazine between 3 and 6 months, and the other variables measured at 3 months, are shown in Table 3. Only the correlation between compliance and the self-efficacy with regard to the use of sulphasalazine tablets is statistically significant. In order to assess if our operationalisation of self-efficacy could function as a predictor of compliance, a logistical regression analysis was performed with a cut-off point of 80%, a compliance rate of at least 80% considered as compliant. Compliance had been measured in the period between 3 and 6 months. We did not find statistically significant differences in the baseline characteristics, between the 37 patients analyzed in the logistical regression

Table 2 Personal factors, perceived environmental influences and perceived barriers regarding the use of sulphasalazine at 3 months (mean [standard deviation]) Self-efficacy expectation (1–5) Outcome expectation (1–5) Perceived social attitude (1–5) Percieved social support (1–5) Percieved barriers (1–5)

Exp Contr Exp Contr Exp Contr Exp Contr Exp Contr

4.4 [1.2] m 54 4.6 [1.0] m 52 4.4 [1.0] m 57 4.4 [0.8] m 513 4.3 [1.3] m 54 4.2 [1.4] m 52 3.5 [1.9] m 56 2.8 [1.7] m 52 1.8 [1.0] m 59 1.9 [1.0] m 510

Exp, experimental group (n 5 25); contr, control group (n 5 30); m, number of patients with missing data. No significant differences between groups were found.

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Table 3 Correlations between compliance with sulphasalazine treatment (3–6 months) and other parameters (at 3 months) in the total population Compliance Self-efficacy Outcome expectation Perceived social attitude Perceived social support Age

1.00 0.58 2 0.19 0.24 0.20 0.08

Sex Education level Pain (AIMS) M-HAQ DAS Perceived barriers

2 0.13 2 0.30 2 0.16 2 0.18 2 0.02 2 0.30

Pain AIMS, pain scale of Dutch Arthritis Impact Measurement Scales; M-HAQ, Health Assessment Questionnaire; DAS, Disease Activity Score. Table 4 Logistical regression analysis a for compliance with sulphasalazine (3–6 months) as dependent factor (n 5 37): independent factors at 3 months Independent variable Included Experimental condition Self-efficacy Excluded Outcome expectation Percieved social attitude Percieved social support Age Sex Level of education Pain (AIMS)a M-HAQ a DAS a Perceived barriers

B

Significance

0.63 3.02

0.49 0.01 0.87 0.19 0.15 0.75 0.51 0.59 0.28 0.66 0.52 0.37

Pain AIMS, pain scale of Dutch Arthritis Impact Measurement Scales; M-HAQ, Health Assessment Questionnaire; DAS, Disease Activity Score. a Model: P 5 0.0004; odds ratio 5 28.

analysis and the remaining 18 patients. Twenty-six patients were compliant, and 11 patients were not compliant. The study condition was entered as first variable. The other independent variables had been measured at 3 months. The results are presented in Table 4, showing that only self-efficacy was a significant predictor.

4. Discussion To examine the factors possibly related with compliance we analyzed the data of patients


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cooperating in a clinical trial on the effect of patient education. The total population (experimental group plus control group) could be analyzed because the level of compliance with DMARD therapy was comparable in both groups [27]. We chose to compare the self-efficacy and outcome expectations regarding DMARD therapy during DMARD therapy and the adherence in the following 3 months period. We did so because we feel that self-efficacy and outcome expectation assessments are not realistic when patients do not have experience with the therapy. However, self-efficacy could be assessed immediately before the start of the treatment if an extensive explanation of the aims and the possible problems of the therapy is given, as well as a demonstration of the tablets and the packaging. Sixty-five patients were asked to cooperate in the study. Sixty gave informed consent. Correlation coefficients could be calculated in the 47 patients to whom sulphasalazine still was prescribed in the period between 3 and 6 months after the study began (Table 3). Data were not complete for 12 of these patients and therefore logistical regression analysis could be performed in only 37 patients (Table 4). Because the number of subjects available is limited, the authors realize that regression analysis is only an indication that self-efficacy might predict compliance in the future. We found a positive correlation between the selfefficacy and the compliance. In contrast we did not find relations between compliance and outcome expectations, perceived attitudes and perceived support of the social environment, demographic variables, disease-related variables, or perceived barriers. Because the number of subjects available is limited, the authors realise that multivariant analysis is only an indication that self-efficacy predicts compliance in future (Table 5). In the study of Beck et al. [26], no correlation was found between the self-efficacy expectation and the compliance with salicylate medication. NSAID therapy in RA, however, is fundamentally different

from DMARD therapy, both regarding the effects to be expected and concerning the patient instructions required. NSAIDs are rapidly acting drugs (hours) with short-lasting effect of pain relief (hours or days), without any effect on the disease process itself. They can be used continuously or as an optional drug. Treatment with DMARD therapy is prescribed to change the disease process, and should be used continuously. Effects of this therapy on the disease process, and consequently on the symptoms, can be expected only after weeks or months. As pain in RA changes in time, the necessity of the NSAID use changes in time. This will impede a good assessment of the self-efficacy regarding the compliance. The existence of a correlation between compliance and self-efficacy opens the perspective of potential application of self-efficacy measurement as a predictor of compliance. An assessment of the future compliance of patients, or groups of patients, would be helpful in the selection of people for patient education. Probably the measurement of compliance with prescribed medication in the preceding period would be a good predictor for future compliance. Performing a pill count, however, is a quite elaborate procedure. Assessing the compliance by questionnaires probably is less valid [7,36]. The use of electronic measurement methods is even more elaborate than applying pill counting, and its use might influence the compliance of patients more severely [7,37]. The measurement of the self-efficacy expectation regarding the use of prescribed medication is easy to perform, and a correlation with compliance is found in this study. A logistical regression analysis revealed that self-efficacy is the only factor that discriminates between compliant and non-compliant patients, using a cut-off point of 80%. Further study on the development of a test that predicts compliance is needed. If the same cut-off point between being compliant or non-compliant is used, the implementation of the self-efficacy measurement could possibly be improved by examining self-efficacy regarding

Table 5 Practical implications (1) (2)

Assessments of self-efficacy might help to differentiate between patients that will be compliant and those that will be not Patients that will benefit additional patient education might be identified by measuring self-efficacy


‘‘the use of at least 80% of the number of sulphasalazine tablets prescribed’’, rather than ‘‘the use of the prescribed sulphasalazine exactly as prescribed’’. The results of our study suggest that self-efficacy with regard to the use of prescribed medication is related to adherence. Further study is needed on the development of an instrument that can be used to predict compliance with medication.

Acknowledgements

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The study was supported by a grant from the Nationale Commissie Chronisch Zieken (National Committee for the Chronically Ill).

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