Abstract

INTRODUCTION

Systemic hypertension (SH) is recognized as a significant public health problem with advances in identifying risk factors, early diagnosis, use of extensive drug treatments and educational campaigns to change lifestyles. In spite of this, it is a disease which is difficult to control and maintaining pressure within the recommended limits is not satisfactory. This evinces the problem of poor adherence to treatment.⁴4 . Damasceno PDL, Lima NM, Lucena LS, Vasconcelos SMM, Moreira TMM. Estudo da adesão ao tratamento farmacológico da hipertensão arterial. Rev Eletronica Pesq Med. 2008;2(4):41-8.

It is estimated that around 50.0% of individuals living with chronic disease do not follow their treatment properly.⁵5 . DiMatteo MR. Variations in patient’s adherence to medical recommendations: a quantitative review of 50 years of research. Med Care. 2004;42(3):200-9. DOI:10.1097/01.mlr.0000114908.90348.f9 In Malaysia, around 44.2% of hypertensive individuals followed their medical treatment properly.⁸8 . Hassan NB, Hasanah CI, Foong K, Naing L, Awang R, Ismail SB, et al. Identification of psychosocial factors of noncompliance in hypertensive patients. J Hum Hypertens. 2006;20(1):23-9. DOI:10.1038/sj.jhh.1001930 In Chile, 21.6% of hypertensive individuals aged over 65 followed treatment.¹⁰10 . Mendoza-Parra S, Muñoz PM, Merino EJM, Barriga OA. Determinant factors of therapeutic compliance in elderly hypertensive patients. Rev Med Chil. 2006;134(1):65-71. In Brazil, the figures for control varied from 10.1% in Tubarao, SC, Southern Brazil, in 2003, to 52.4% in Sao José do Rio Preto, SP, Southeastern Brazil, from 2004 to 2005, considering population based studies of hypertensive individuals undergoing treatment, the control criteria of which were systolic and diastolic blood pressure levels of < 140/90 mmHg, respectively.¹²12 . Piccini RX, Facchini LA, Tomasi E, Siqueira FV, Silveira DS, Thumé E, et al. Promoção, prevenção e cuidado da hipertensão arterial no Brasil. Rev Saude Publica. 2012;46(3):543-50. DOI:10.1590/S0034-89102012005000027

Non-adherence occasions unnecessary adjustments to treatment regimens due to lack of positive response to treatment, increasing health care costs with higher rates of hospitalizations and treating complications. Moreover, it frustrates the efforts of health care professionals as it impedes their achieving objectives outlined for the health care of hypertensive individuals.¹¹11 . Miranzi SSC, Ferreira FS, Iwamoto HH, Pereira GA, Miranzi MAS. Qualidade de vida de indivíduos com Diabetes Mellitus e Hipertensão acompanhados por uma equipe de saúde da família. Texto Contexto Enferm. 2008;17(4):672-9. DOI:10.1590/S0104-07072008000400007 ^{, 13}13 . Pinho NA, Pierin AMG. Hypertension control in brazilian publications. Arq Bras Cardiol. 2013;101(3):65-73. DOI:10.5935/abc.20130173

Measuring adherence to SH treatment is a complex task. Different methods have been applied, there are different cutoff points and there is no method considered to be the gold standard and which represents the various dimensions involved in the process of adherence to treatment for this syndrome.¹⁷17 . Santa Helena ET, Nemes MIB, Eluf-Neto J. Desenvolvimento e validação de questionário multidimensional para medir não-adesão ao tratamento com medicamentos. Rev Saude Publica. 2008;42(4):764-7. DOI:10.1590/S0034-89102008000400025

The majority of methods used to evaluate adherence to SH treatment focus only on pharmacological treatment, and are also applied to other diseases. There is a gap to be filled.

One alternative for this measurement lies in item response theory (IRT). This theory includes a set of models for latent variables which propose to represent the relationship between the probability of a respondent giving a certain response to an item and their latent trait (characteristic of the individual which cannot be directly observed). This characteristic is measured using secondary variables related to it.¹1 . Andrade DF, Tavares HR, Valle RC. Teoria da Resposta ao Item: conceitos e aplicações. São Paulo: Associação Brasileira de Estatística; 2000.

The aim of this study was to draw up and validate a questionnaire on adherence to SH (QATSH) treatment based on IRT.

METHODS

Methodological study based on modern psychometrics (IRT) following the three procedures for constructing evaluation instruments: theoretical, empirical and analytical.¹⁴14 . Pasquali L, Primi R. Fundamentos da Teoria da Resposta ao Item – TRI. Avalial Psicol. 2003;2(2):99-110. ^{, 15}15 . Pasquali L. Psicometria: Teoria dos testes na psicologia e na educação. São Paulo: Vozes; 2009.

At the theoretical stage, an integrative revision was constructed seeking to discover conditioning factors specific to the treatment of this syndrome. The constitutive and operational definitions were described and items drawn up for the measuring instrument based on the 12 criteria recommended by Pasquali (breadth, balance, behavior, simplicity, clarity, relevance, accuracy, modality, typicality, objectivity, variety and credibility).¹⁵15 . Pasquali L. Psicometria: Teoria dos testes na psicologia e na educação. São Paulo: Vozes; 2009.

The first version of the instrument underwent semantic analysis to verify understanding of the items. Two groups of four individuals with different levels of schooling and of different ages were formed from individuals attending the Centro Integrado de Hipertensão e Diabetes (CIDH - Integrated Center for Hypertension and Diabetes) in Fortaleza, CE, Northeastern Brazil, in 2012. Changes were made to the phrasing of seven items to correct misunderstanding.

The proposal for the instrument was sent to a panel of experts for the phrasing and understanding of the items to be assessed, along with its conceptual pertinence regarding adherence to SH treatment. Five experts agreed to participate in the research: one doctor, two nurses, a nutritionist and a physical education professional. Each received a 20-item guide to evaluating the instrument. Evaluations were compared and suggestions with agreement of 80.0% or over were included.¹⁵15 . Pasquali L. Psicometria: Teoria dos testes na psicologia e na educação. São Paulo: Vozes; 2009. Several items were excluded (2, 3, 4, 5, 14), others were reformulated (6, 7, 11, 12, 13, 15, 18) and new items included (12, 13, 14). After evaluation by the expert panel, QATSH consisted of 23 items, which were standardized regarding wording and domain.

The empirical procedure encompassed applying the instrument. QATSH was applied to 1,000 individuals with SH under treatment in the CIDH.

As this concerns constructing and validating an instrument using IRT, it was necessary to have a sample large enough to ensure respondents covering all the latent traits studied. There is no consensus on the ideal number of respondents.¹1 . Andrade DF, Tavares HR, Valle RC. Teoria da Resposta ao Item: conceitos e aplicações. São Paulo: Associação Brasileira de Estatística; 2000. However, large samples with ≥ 1,000 respondents have a greater chance of covering all latent traits studied.

The analytical stage aimed to validate the instrument using psychometric analysis and statistical procedures to verify the reliability, validity, estimated parameters of the items and level of adherence to SH treatment (parameters of the individuals) through an IRT model.

The internal consistency of the set of items was analyzed using Cronbach’s alpha (α) and the psych ^aa Revelle W. Psych: procedures for psychological, psychometric, and personality research. Evanston; 2010 [cited 2012 May 24]. Available from: http://cran.univ-lyon1.fr/web/packages/psych package of free software R^bb R Development Core Team. R: a language and environment for statistical computing. Version 2.13.2.Vienna: R Foundation for Statistical Computing; 2011. was used.

Factor analysis of the complete information was conducted based on response theory models to a multi-dimensional item (MIRT)¹⁸18 . Wirth RJ, Edwards MC. Item factor analysis: current approaches and future directions. Psychological Methods. 2007;12(1):58-79. DOI:10.1037/1082-989X.12.1.58 to understand the latent traits (or subjacent factors) associated with the instrument’s response patterns. It is possible to evaluate correlation between the items and possible latent traits (or subjacent factors) through this analysis, enabling it to be verified whether all items belong to a one-dimensional model or whether there are subsets of items justifying other dimensions. This analysis was conducted using the mirt ³3 . Chalmers RP. Mirt: a Multidimensional Item Response Theory Package for the R Environment. J Stat Softw. 2012;48(6):1-29. package of free software R.^bb R Development Core Team. R: a language and environment for statistical computing. Version 2.13.2.Vienna: R Foundation for Statistical Computing; 2011.

The parameters of the items (a and b) were estimated using Multilog software^cc Thissen D, Chen W, Bock R. Multilog, version 7 [computer software]. Lincolnwood: Scientific Software International; 2003. at the stage of calibrating the items. It was observed that there was convergence of the algorithm used in applying the estimation method. The Samejima¹⁶16 . Samejima FA. Estimation of latent ability using a response pattern of graded scores. Psychometrika. 1970;35:139. gradual response model was used to analyze the items.

The proficiency (θ) of the respondents was estimated using the marginal maximum likelihood (MML) method in two stages: parameters of abilities were separately integrated and the item parameters were estimated. When the item parameters were estimated, adherence to SH treatment (parameters of the individuals) were predicted.

Next, a scale was created for these latent traits. The anchor items were defined. An item is an anchor for level Z if it meets three conditions for Y< Z:¹1 . Andrade DF, Tavares HR, Valle RC. Teoria da Resposta ao Item: conceitos e aplicações. São Paulo: Associação Brasileira de Estatística; 2000. simultaneously

Given the difficulty in meeting all of these conditions, it was decided to be more flexible with these criteria and consider the anchor level that which met two conditions of those described above, as well as considering probability of > 60.0% in determining the anchor level of the scale.

The values for the item parameters (a, b) and for scores for adherence to SH treatment were estimated on the same metric in the scale with mean 0 and standard deviation (SD) 1.0. These values were transformed using mean 100 and SD 10, i.e., scale (100,10) to improve the comprehensibility of the results.

The study was approved by the Research Ethics Committee of the Universidade Estadual do Ceará (UECE), Process 11517971-2. All participants signed an informed consent form.

RESULTS

It was possible to construct a theoretical explanation and definition of the domain of the construct from an integrative review of the domains that influence adherence to SH treatment (Table 1). The 20 initial QATSH items were drawn up based on this definition.

The QATHAS had Cronbach’s alpha (α) of 0.81.

The first factor explained 22.4% of total variance, evidencing a dominant factor.

The initial 23-item instrument underwent calibration. However, the algorithms of these items did not converge and alterations were necessary in response categories and items were excluded.

Items referring to medication, salt, fat, sweets and physical exercise remained in the initially proposed response categories. Items referring to medication dosage and times remained with four response categories, whereas that referring to white meat intake remained with two response categories.

Items referring to homemade remedies, cigarettes, illegal drugs, alcohol, fruit and vegetable consumption, weight, attending appointments, stress, complications and hospitalization during treatment were excluded from the final analysis. Their presence did not permit convergence of the estimation algorithm, as well as having low parameter a values (parameter of discrimination being very low, i.e., not discriminating hypertensive individuals with low adherence to SH treatment from those with high (Annex)).

Table 2 shows estimates of the parameters of the items, discriminating the dimensions of analysis, the 12 QATSH items and the a parameters (parameter of discrimination), b ₂ , b _3, b ₄ and b ₅ (parameters of difficulty) for categories 2, 3, 4 and 5 of the Likert scale. It is assumed that the data follow normal distribution, with μ = 0 and s = 1, i.e., scale (0.1) for initial determination of the parameters.

The QATSH was shown to have high error (curve in red) from level 0.5 of the scale onwards, compared with the information curve (Figure).

The scale is based on ten of the twelve QATSH items based on the previously described anchor levels. The initial instrument had items including all of the dimensions involved. The item referring to the environmental dimension was excluded during calibration as it did not allow convergence of estimates of items. The scale included items referring to three domains: disease/treatment, user and health care services.

When responding to the QATSH, in contrast to questionnaires using classical test theory, the result is not obtained from adding up points or scores. The calculation is made using a mathematical formula which uses the values of the parameters of the items (a and b) and of a constant. A free web site was set up and made available^dd Rodrigues MTP, Moreira TMM. Questionário de adesão ao tratamento da hipertensão arterial sistêmica. Fortaleza, 2012. Available from: www.qathas.com.br containing access to the instrument and to the results. On this site, each health care professional can enter the responses of users examined and see the level of the scale (Table 3) at which each respondent is situated. Levels of adherence vary between 60 and 110, i.e., hypertensive individuals with lower adherence reach 60, while those who adhere more are located at level 110.

DISCUSSION

The grouping of the response categories and the exclusion of certain items during calibration show the difficulty of constructing items with high parameters of discrimination. The items were constructed following rigorous scientific methodology, based on theoretical knowledge of the latent trait studied and meeting basic construction criteria.¹⁴14 . Pasquali L, Primi R. Fundamentos da Teoria da Resposta ao Item – TRI. Avalial Psicol. 2003;2(2):99-110. ^{, 15}15 . Pasquali L. Psicometria: Teoria dos testes na psicologia e na educação. São Paulo: Vozes; 2009. In spite of this, some of them had poor discriminatory power and had to be eliminated. Drawing up instruments requires paying attention to the construction of the items, clarity of approach and focus on the latent trait to strengthen discriminatory power and produce items with high a parameters.

The lack of convergence may be due to the following factors: the item being poorly drawn up, low number of respondents, not discriminating those who adhered to treatment from those who did not, the item being incompatible with the dimension of analysis or a combination of these factors.

Items related to non-medical treatment (6 to 11) stood out in the exclusion. An alternative for this result is reformulating the items to make them more discriminatory, i.e., possessing a greater quantity of psychometric information and better discrimination.

A curious, and apparently contradictory, finding was the exclusion of the item referring to the figure for blood pressure (BP), as this value is a direct way of knowing if it is being controlled (clinical response). This may be explained by it being an isolated measure, representing just one moment in time. Moreover, the procedure for measuring AP is vulnerable to error, as it should be done properly, e.g., with the patient appropriately prepared, using a standardized technique and calibrated equipment.⁶6 . Diretrizes brasileira de hipertensão arterial. Rev Bras Hiper. 2010;17(1):4-63.

The majority of respondents did not use homemade remedies, cigarettes, illegal drugs or alcohol, meaning there was no convergence of the estimation algorithm. An alternative for convergence would be to apply these items to hypertensive users who did use these substances and have respondents for all response categories.

Regarding the interpretation of the a parameter, discrimination of the item, values of > 0.6 are acceptable. The higher the a value, the higher the item’s discriminatory power.¹1 . Andrade DF, Tavares HR, Valle RC. Teoria da Resposta ao Item: conceitos e aplicações. São Paulo: Associação Brasileira de Estatística; 2000. None of them had values inferior to the acceptable value for this parameter (Table 2), suggesting that the items remaining in the final instrument were able to discriminate individuals with better adherence to SH treatment from those with poorer adherence.

Items referring to medication performed well when some kind of symptom was felt (4) and for fat intake (7), as they were better at discriminating individuals adhering to SH treatment compared to those who did not.

Many hypertensive users only used their medication when they had symptoms of high pressure. Thus, they did not adhere satisfactorily to treatment, as anti-hypertension medicine should be taken continuously, whether there are symptoms or not. For those hypertensive individuals with a satisfactory level of adherence to treatment, medication was taken daily, without being associated with the appearance of any symptom. This context explains the higher discriminatory power of this item. Leão & Silva et al⁹9 . Leão e Silva LO, Soares MM, Oliveira MA, Rodrigues SM, Machado CJ, Dias CA. “Tô sentindo nada”: percepções de pacientes idosos sobre o tratamento da hipertensão arterial sistêmica. Physis. 2013;23(1):227-42. DOI:10.1590/S0103-73312013000100013 (2013) stated that poor adherence was associated with not having symptoms, as “not feeling anything” is understood to be absence of illness, making regular medication use unnecessary.

Low calorie food with low saturated fat, cholesterol and total fat content is recommended, as is eating a diet rich in fruit and vegetables. This has a significant impact on reducing AP, as well as reducing biomarkers of cardiovascular disease.⁶6 . Diretrizes brasileira de hipertensão arterial. Rev Bras Hiper. 2010;17(1):4-63. However, it can be difficult to follow this kind of diet, given the availability of ready prepared foods, generally with high calorie content. The cultural context in which hypertensive individuals find themselves also affects the intake of food with a high fat content. There are few individuals who manage to abandon fatty foods and follow the diet recommended for hypertensive individuals, so this is an item with good discrimination.

Items with lower power of discrimination were those concerning having neglected to take medication at some point (1) and white meat intake (8). The expression “have you ever” in item 1 can refer to an isolated episode or to a frequent practice. Even those with the best adherence can neglect to take their medicine at some point, explaining the poorer discriminatory power of this item.

Hypertensive individuals reported two reasons for high white meat consumption: it being cheaper than red meat and preference. Mentioning the fact that white meat was healthier was the exception, and this explains the poor discriminatory power of this item.

The difficulty of the item was measured by parameter b, indicating the position on the scale at which the item has the greatest information. The higher the value of parameter b, the greater the difficulty of the item. The items which were most difficult to respond to were those regarding doing physical exercise (10) and routinely following non-pharmacological treatments (11), referring to non-pharmacological treatment. As they are the items to which it is most difficult to respond satisfactorily, they tend to be more representative of individuals who adhere to treatment.

Doing aerobic exercise (especially isotonic), which should be complemented by resistance exercises, helps to lower AP and is recommended for preventing and treating SH. The recommendation is to develop the habit of doing regular aerobic exercise, such as walking for 30 minutes a day, three times/week for prevention, and daily for treatment.⁶6 . Diretrizes brasileira de hipertensão arterial. Rev Bras Hiper. 2010;17(1):4-63. A peculiarity of SH is that it mainly affects older adults, as shown in this study: 66.1% of those interviewed were aged 60 or over, leading to limitations imposed by age. Many hypertensive individuals also suffer from other health problems, including sequelae of other diseases impeding them from doing exercise.

Urban violence was mentioned as a factor that makes it more difficult to do regular physical activity in public areas or areas near the home.

Despite the lifestyle changes occurring in the Brazilian population, habits that are harmful to health, such as sedentarism, still predominate among users with hypertension.²2 . Carvalho ALM, Leopoldino RWD, Silva JEG, Cunha CP. Adesão ao tratamento medicamentoso em usuários cadastrados no Programa Hiperdia no município de Teresina (PI). Cienc Saude Coletiva. 2012;17(7):1885-92. DOI:10.1590/S1413-81232012000700028 ^{, 7}7 . Guedes MVC, Araújo TL, Lopes MVO, Silva LF, Freitas MC, Almeida PC. Barreiras ao tratamento da hipertensão arterial. Rev Bras Enferm. 2011;64(6):1038-42. DOI:10.1590/S0034-71672011000600008 Regular physical activity is an obstacle to adherence to SH treatment.⁷7 . Guedes MVC, Araújo TL, Lopes MVO, Silva LF, Freitas MC, Almeida PC. Barreiras ao tratamento da hipertensão arterial. Rev Bras Enferm. 2011;64(6):1038-42. DOI:10.1590/S0034-71672011000600008 ^{, 9}9 . Leão e Silva LO, Soares MM, Oliveira MA, Rodrigues SM, Machado CJ, Dias CA. “Tô sentindo nada”: percepções de pacientes idosos sobre o tratamento da hipertensão arterial sistêmica. Physis. 2013;23(1):227-42. DOI:10.1590/S0103-73312013000100013

Another item to which it was difficult to respond satisfactorily was routinely following non-pharmacological treatment (11). This is a very broad item and covers all non-pharmacological measures recommended for treating SH: weight control, eating patterns, moderate alcohol and tobacco consumption, physical exercise and controlling stress. As it covers many changes in lifestyle, it is an item which is more difficult to fulfill. Studies have shown the difficulty in following non-pharmacological treatment.²2 . Carvalho ALM, Leopoldino RWD, Silva JEG, Cunha CP. Adesão ao tratamento medicamentoso em usuários cadastrados no Programa Hiperdia no município de Teresina (PI). Cienc Saude Coletiva. 2012;17(7):1885-92. DOI:10.1590/S1413-81232012000700028 ^{, 7}7 . Guedes MVC, Araújo TL, Lopes MVO, Silva LF, Freitas MC, Almeida PC. Barreiras ao tratamento da hipertensão arterial. Rev Bras Enferm. 2011;64(6):1038-42. DOI:10.1590/S0034-71672011000600008 ^{, 9}9 . Leão e Silva LO, Soares MM, Oliveira MA, Rodrigues SM, Machado CJ, Dias CA. “Tô sentindo nada”: percepções de pacientes idosos sobre o tratamento da hipertensão arterial sistêmica. Physis. 2013;23(1):227-42. DOI:10.1590/S0103-73312013000100013 ^{, 12}12 . Piccini RX, Facchini LA, Tomasi E, Siqueira FV, Silveira DS, Thumé E, et al. Promoção, prevenção e cuidado da hipertensão arterial no Brasil. Rev Saude Publica. 2012;46(3):543-50. DOI:10.1590/S0034-89102012005000027

Items referring to salt intake (6), consumption of sweets and sugary drinks (9) and attending appointments (12) had intermediate b parameter values compared with other items in the QATSH, with a medium level of discrimination and difficulty.

Not all of the proposed domains were kept in the final instrument. Some items were excluded as the estimates did not converge, or for having very low a parameter values, i.e., for not discriminating hypertensive individuals with poor adherence to treatment from those with high adherence. The need remains to create and validate items which include all domains involving adherence to SH treatment.

The QATSH was shown to be better at measuring poor adherence to treatment than high adherence. This study contributes to the current Brazilian and world context, characterized by high rates of poor adherence to SH treatment. It is essential that there is an instrument to better identify users with low adherence to treatment, as they are the ones who need to modify their behavior and improve adherence to SH treatment.

Drawing up a list of goals with the patient, according to their individual score, is an innovation of this instrument. Patients at level 70 on the scale know that they need to be more rigorous in taking their medication on time in order to ascend to level 80 on the scale. This facilitates patients’ understanding and improves the health care professional’s degree of control and decision making. The health care team can make use of a variety of strategies to present the results to the patient, as well as the positive reinforcement of being able to demonstrate improvements in adherence on the scale.

Both the patient and the health care professional perceive advances in treatment with greater clarity, as it facilitates detecting and measuring fulfillment of prescribed treatment, as well as making it viable to establish goals to be achieved. This differential was possible through the use of IRT which, in contrast to the classical test teory (TCT), uses (θ) constructed item by item, rather than only the sum of correct items.

References

Annex   Questionnaire on adherence to treatment of systemic hypertension (QATSH). Fortaleza, CE, Northeastern Brazil, 2012.

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