An Evaluation of Medication Adherence in Tuberculosis Patients

Based on Theory of Planned Behavior

Novian Mahayu Adiutama

, Muhammad Amin

and Abu Bakar

Faculty of Nursing Universitas Airlangga, Kampus C Mulyorejo, Surabaya, Indonesia

Faculty of Medicine Universitas Airlangga Kampus C Mulyorejo, Surabaya, Indonesia

Keywords: Attitude, Behavior, Medication Adhrence, Theory of Planned Behavior, Tuberculosis.

Abstract: Medication adherence in TB (tuberculosis) becomes a crucial factor in achieving success of treatment. The

aim of this study was to assess the medication adherence of TB patients and to identify the predictors based

on TPB (Theory of Planned Behavior). Cross-sectional studies were conducted in patients of TB with

positive AFB (Acid-Fast Bacilli) test at a hospital in Pacitan District (N = 113), (n = 104) patient agreed to

participate this study. Recruitment of the respondent was used total sampling method. Data collection was

conducted from November 2017 to February 2018. The instrument in this study was developed in

accordance with standard guideline of TPB, medication adherence was measured using MMAS-8. Multiple

linear regression used to identify predictors. Mean score of medication adherence was 4.09 (SD = 0.936)

(range of possible score = 1-8). ATB (Attitude Toward Behavioral) (p = 0,02), SN (Subjective Norm) (p =

0.00), and PBC (Perceived Behavior Control) (p = 0.00) significantly predicted intention (R Square = 0965),

then intention may affect medication adherence (p = 0.00). The constructs of TPB, namely ATB, SN, PBC,

and Intention significantly predicted medication adherence of TB patients. This study supports an

investigation about the factors underlying medication adherence on a larger scale, as well as the

identification of targets in designing future interventions.

1 BACKGROUND

Tuberculosis is an infectious disease that becomes a

major health concern (Pang et al., 2018).

Tuberculosis control with the DOTS strategy has

been implemented in many countries since 1995, but

still remains global problem which is difficult to be

solved (WHO, 2015).

Indonesia is one of the world largest tuberculosis

contributors, ranks second after India which is 10%

of all patients in the world (WHO, 2015). This

becomes very serious problem because of its long

treatment period and requires high adherence of the

patients.

Drug resistance is one result of poor medication

adherence, either due to dose problems or failure in

completing treatment program (Guix-Comellas et

al., 2017). The average of patient adherence in long-

term treatment program in developed countries is

only 50%, while lower numbers are found in

developing countries (WHO, 2015). Adherence of

treatment program has an important role to prevent

transmission, death from TB, recurrence and drug

resistance (Addisu et al., 2014). The measurement of

adherence is important in order to achieve the

success of treatment (Browne et al., 2018).

TB patients are required to have high adherence

in treatment program as an effort to reduce the

burden of TB. Therefore, this study is intended to

measure TB treatment adherence and identify factors

that may affect adherence itself.

This study was used Theory of Planned Behavior

(TPB) as the conceptual framework. TPB explains

that intention is a direct predictor of behavior, which

in this case is behavior of TB patient in completing

their treatment programs. While the intention itself

comes from the main factors of TPB, namely ATB,

SN, and PBC (Ajzen, 2005). The main factors of

TBP are shown to have a close relationship with the

intention(Miller et al., 2015). The constructs of TBP

can predict a person's intentions until behavior is

formed (Peleg et al., 2017).

Thus, the idea in this study is Theory of Planned

Behavior can also explain how medication

adherence in TB patients. In this study, we explore

factors associated with medication adherence in TB

428

Adiutama, N., Amin, M. and Bakar, A.

An Evaluation of Medication Adherence in Tuberculosis Patients Based on Theory of Planned Behavior.

DOI: 10.5220/0008326204280434

In Proceedings of the 9th International Nursing Conference (INC 2018), pages 428-434

ISBN: 978-989-758-336-0

patients based on the construct of TPB. The aim of

this study was to assess the medication adherence of

TB patients and to identify the predictors based on

TPB (Theory of Planned Behavior).

2 METHODS

2.1 Respondent and Procedure

Cross-sectional studies were conducted in patients of

TB with positive AFB (Acid-Fast Bacilli) test at a

hospital in Pacitan District (N = 113). Recruitment

of the respondent was used total sampling method.

Data collection was conducted from November 2017

to February 2018. Respondents consisted of all TB

patients with positive AFB and were over 15 years

of age. Patients with co-morbid conditions (such as,

psychiatric illness, neoplasia) and patients who did

not complete the questionnaire were excluded from

the study. A total of (n = 104) from 113 eligible

respondents agreed to participate this study

(recruitment rate 92.03%). The informed consent

was obtained from all respondents before they

participate in this study. This study protocol has

been approved by the Indonesian Commission of

Health Research Ethics.

2.2 Instrument

Questionnaire was used in data collection process.

The medication adherence was measured using

MMAS-8(Morrisky Medication Adherence Scale-8),

while ATB, SN, PBC, and Intention were measured

using instruments developed from standard

instruments of TPB.

2.2.1 Medication Adherence

The medication adherence was measured using

MMAS-8 (Morisky et al., 2008) that has been

modified as needed. The instrument was written in

Indonesian, and there was 8 items of questions with

a range of scores each question (0-1). The score

were summed, and the higher score showed the

higher adherence level. This questionnaire has been

tested for its validity and reliability. Validity test

used pearson product moment with 5% significance

level, and the result showed that all item of the

questionnaire are valid. Reliability test used alpha

cronbach with 5% significance level, and the result

showed reliable.

2.2.2 Attitude Toward Behavioral

The measurement of this variable was used the

instrument which consist of 10 questions, and it is

divided into 2 paired sections. The first section was

the questions about outcome evaluation as many as 5

items of questions, and the second section was about

strenght beliefs as many as 5 items of questions.

Range of scores each question (1-7) (Semantic

Differential). ATB scores were calculated using the

following formula (Ajzen, 1991):

AB = ∑ b

Keterangan:



AB : Attitude Toward Behavioral



: Strengt beliefs



: Outcome evaluation

2.2.3 Subjective Norm

The measurement of this variable was used the

instrument which consist of 10 questions, and it is

divided into 2 paired sections. The first section was

the questions about motivation to comply as many as

5 items of questions, and the second section was

about normative beliefs as many as 5 items of

questions.

Range of scores each question (1-7) (Semantic

Differential). SN scores were calculated using the

following formula(Ajzen, 1991):

SN = ∑ n

. m

Keterangan:



SN : Subjective norm

Attitude

Toward

Behavioral

Subjective

Norms

Perceived

Behavioral

Control

Intention Behavior

Figure 1: Construct of theory of planned behavior.

An Evaluation of Medication Adherence in Tuberculosis Patients Based on Theory of Planned Behavior

429

 n

: normative beliefs



: motivation to comply

2.2.4 Perceived Behavior Control

The measurement of this variable was used the

instrument which consist of 10 questions, and it is

divided into 2 paired sections. The first section was

the questions about beliefs control as many as 5

items of questions, and the second section was about

power beliefs as many as 5 items of questions.

Range of scores each question (1-7) (Semantic

Differential). PBC scores were calculated using the

following formula(Ajzen, 1991):

PBC = ∑ c

. p

Keterangan:



SN : Subjective norm



: control beliefs



: Power beliefs

2.2.5 Intention

The Intention questionnaires which modified from

TPB Quissionariewas used as the measurement of

intention (Ajzen, 1991). Modifications were made to

the question form as well as the content of the

questions to match the theme of the study, so the

researchers tested the validity and reliability of the

questionnaire, and the results showed that the

questionnaire was valid and reliable.

This variable measurement questionnaire

consists of 10 question items. Range of scores for

each question (1-7) (Sisctematic Differential). The

score were summed, and the higher the score

showed the higher the intention level.

2.3 Statistical Analysis

Data were analyzed using SPSS version 22. Multiple

linear regression was used to identify the ATB, SN,

PBC variables contribution to Iintention. Simple

linear regression was used to determine the effect of

intention on medication adherence, and the direct

effect of PBC on medication adherence.

Confounding variables in this study were gender,

education, occupation, and age. The specified

significance level was p <0.05.

3 RESULTS

Socio demographic characteristics in table 1 showed

a total of 104 respondents in this study gave a

response of 100%. The average age of respondents

was 43.65 years. More than half of respondents

(54.8%) were male. A total of 63.3% of respondents

had graduated from elementary school, 29.8%

graduated from high school, and 1.9% graduated

from college. Most respondents (71.2%) work as

private employees, 3.8% of civil servants, 1.9%

police/military, and 23.1% were not employed.

Table 1: Predicting medication adherence from demographic characteristics (n = 104).

Frequency (%) Mean SD Sig.

Age

Gender:

Male

Female

Education

Elementary school

High school

College

Occupation

Civil servants

Private employees

Police/military

Not employed

54.8

45.2

68.3

29.8

1.9

3.8

71.2

1.9

23.1

43.65 14.47 .011

.989

.000

.004

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430

Pearson correlation analysis showed that there was no significant relationship between gender with

medication adherence (p = 0.989), while age,

education status, and occupation were closely related

to medication adherence: age (p = 0.011), education

status (p = 0.00), occupation (p = 0.004).

The mean score of medication adherence as

showed in table 2 was 4.09 (SD = 0.93) (range of

possible score = 0-8). According to the results of the

questionnaire analysis, 4 respondents (3.8%)

sometimes had forgotten to take their medicine. 2

respondents (1.9%) sometimes had not taken the

drug in the last 2 weeks.

Twenty one respondents (20.2%) had not taken

the medicine without telling the doctor because their

condition became worse after taking the medicine.

97 respondents (93.3%) sometimes forgot to bring

medicine while traveling. 98 respondents (94.2%)

feel disturbed or uncomfortable having to take

medicine every day for a long time. 99 respondents

(95.2%) had the desire to stop taking the medication

Table 2: Medication adherence of TB patiens (n = 104).

Item No (f) (%) Yes (f) (%)

1. Do you sometimes forget to take your pills?

2. Over the past 2 weeks, were there any days when you did not take your

medicine?

3. Have you ever cut back or stopped taking your medication without

telling your doctor because you felt worse when you took it?

4. When you travel or leave home, do you sometimes forget to bring along

your medications?

5. Taking medication everyday is a real inconvenience for some people. Do

you ever feel hassled about sticking to your treatment plan?

6. When you feel better, do you sometimes stop taking your medicine?

7. Did you take your medicine yesterday?

8. How often do you have difficulty remembering to take all your

medication?

100

102

96.2

98.1

79.8

6.7

5.8

4.8

17.3

104

3.8

1.9

20.2

93.3

94.2

95.2

100

82.7

Table 3: Frequency distribution of TPB construct.

TPB Construct Mean Median SD Range of Possible Score

Attitude toward behavioral.

Subjective norm.

Perceived behavior control.

Intention.

Behavior (medication adherence of TB patients).

98.65

103.05

137.42

44.65

4.09

100

135

31.11

28.74

21.18

5.77

.93

5 – 245

7 – 70

0 – 8

Table 4: Predicting intention from ATB, SN, and PBC.

R Square B Sig.

Attitude toward behavioral, subjective norm, and percieved

behavior control (

simultaneously).

Attitude toward behavioral.

Subjective norm.

Perceived behavior control.

.965

.041

.074

.110

.000

.020

.000

*Dependent variable: Intention.

Table 5: Predicting medication adherence from

intention and direct from PBC.

R Square B Sig.

Intention.

Perceived behavior

control.

.975

.977

.160

.044

.000

*Dependent variable: Medication adherence of TB

patients.

An Evaluation of Medication Adherence in Tuberculosis Patients Based on Theory of Planned Behavior

431

if they was already healed. The day before filling out

the questionnaire, all the respondents (100%) took

their medicine. 86 respondents (82.7%) had

difficulties in remembering that they should take all

TB medication.

The effect of ATB, SN, and PBC on intention:

The mean of each variable was 98.65 (SD = 31.11)

for ATB variables (range of possible score = 5-245),

103.05 (SD = 28.74) for SN variable (range of

possible score = 5-245), 137.42 (SD = 21.18) for

PBC variable (rang of possible score = 5-245), 44.65

(SD = 5.77) for intention variables (range of possible

score = 7-70).

Multiple linear regression analysis showed that

ATB, SN, and PBC were simultaneously significant

in predicting intention (p = 0.00) (R Square = 0.96),

when viewed from the significance level separately

were (p = 0.02) for ATB, (p = 0.00) for SN, and (p =

0.00) for PBC.

The effect of intention on medication adherence:

Simple linear regression analysis showed that

intention significantly affected medication

adherence (p = 0.00) with (R Square = 0.97).

The direct relationship between PBC with

medication adherence: Simple linear regression

analysis showed that PBC significantly affected

medication adherence (p = 0.00) with (R Square =

0.98).

4 DISCUSSION

Based on this study result, the mean score was 4.09

in the medication adherence of TB patients (range of

possible score 0 - 8), it has been known that

medication adherence has an important role to

prevent transmission, death from TB, recurrence and

drug resistance (Addisu et al., 2014). The analysis of

questionnaire in this study showed that 94.2% of

respondents feel disturbed and uncomfortable with

treatment program of TB that requires them to take

their medication every day for a long time, perhaps

because of the lack of social and psychological

support from their family and their nearest person as

documented in some previous research.A study in

South Africa showed that good social support can

improve adherence in TB patients (Akeju, Wright

and Maja, 2017). Social and psychological

interventions should be optimized to improve

medication adherence in TB patients (Yan et al.,

2017). Good medication adherence can be achieved

by utilizing social influences through education in

family members about how to support medication

adherence to their family (Kopelowicz et al., 2015).

otes: Statistics reported next to arrows are standardized regression coefficients

*ρ < 0.001 ; **ρ < 0.05

ure 2. Extended TPB construct to

redict medication adherence

Attitude Toward

Behavioral

Subjective Norms

Perceived Behavioral

Control

Intention

Behavior

(Medication

Adherence)

β = .218**

β = .369*

β = .404*

β = .988*

β = .989*

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In this study, socio-demographic factors (such as

age, education, and occupation) were correlated with

medication adherence, but not by gender. It is also

reported in a study that the social situation of each

individual can affect medication adherence in TB

patients (Akeju, Wright and Maja, 2017). In addition

to adequate treatment, treatment of TB patients

should pay attention to specific mental and social

needs (Kastien-Hilka et al., 2017). Psychosocial

treatment and other interventions need to be done in

difficult patients (Priwitzer, 2018), and also the

interventions should focus on improving social and

family function (Yin et al., 2018).

The aim of this study was to identify factors that

affect the medication adherence of TB patients based

on Theory of Planned Behavior. The results of the

study showed that the main factors of TPB (such as

ATB, SN, and PBC) explain more than 96% of the

other studies have also suggested that TPB became

positive determinant factor related to adherence (Wu

and Liu, 2016), TPB was also helpful to investigate

factors underlying medication adherence (Bérubé et

al., 2017), so that TPB can be used as powerful tool

to predict intention and medication adherence

(Zomahoun et al., 2016).

This study has limitations because it only

measures medication adherence and does not

measure prevention of transmission and nutritional

compliance, for the further research it is advisable to

measure these variables because considering the

importance of prevention of transmission and

nutritional compliance in the case of tuberculosis.

5 CONCLUSIONS

Based on the discussion above, it can be concluded

that medication adherence of TB patients in

respondents was at low level. Socio-demographic

and constructive factors of TPB can affect the

medication adherence of TB patients, there was also

a direct relationship of PBC with medication

adherence without intention. This study helps health

professionals and researchers in understanding the

medication adherence of TB patients using TPB.

This study supports an investigation about the

factors underlying medication adherence on a larger

scale, as well as the identification of targets in

designing future interventions.

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