Translation and validation of the Malaysian version of generic medicines scale

Abstract

The study aims to translate and validate the generic medicine scale (GMS) among the Malaysian population. A standard “forward–backward” procedure of translation was used and the translated version was then validated on a convenience sample of 202 patients. Face validity of translated GMS was confirmed with pilot testing. Content validity of the translated GMS was evaluated by eight postgraduate students who are experts in the field. For reliability, the instrument demonstrated good internal consistency (Cronbach’s α = 0.734) with correlation coefficient ranging from 0.198 to 0.500. Alpha value for efficacy dimension of the scale was 0.623 and for similarity dimension was 0.716. The test–retest reliability of the GMS indicates good reliability and stability of the instrument with Spearman’s rank correlation coefficient of 0.532 (r_s = 0.532, n = 202, p = 0.005). In conclusion, the Malaysian version of the GMS is a reliable and valid measure of patients’ belief about generic medicines.

Keywords

Generic Medicines Scale generic medicine translation validation Malaysia

Introduction

Globally, the healthcare expenditure has increased significantly over the years.^1,2 Pharmaceutical cost has been reported as the second main driver for healthcare cost escalation after healthcare professional wages.³ Similar trend has been noticed in the current Malaysian healthcare system. Greater use of generic medicines is identified as one of the methods suggested to curb the escalating cost of medicine.^4–7 Cost-saving benefit of generic medicine was confirmed by previous studies.^7,8 In fact, in Malaysia, it was reported that potential savings of up to 60% for consumers through generic substitution can be achieved.^9,10 Possible factors for escalating healthcare cost were increase in elderly population, rise in incidence of so-called developed-country illness, awareness of healthcare service grows, and access to healthcare service improves.¹¹

Malaysian government identified the cost-saving benefits of generic medicines and has formulated few policies for encouraging the greater use of generic medicines. Under the third component of Malaysia National Medicine Policy which was officially been launched in 2007, the government had formulated the Generic Medicine Policy that advocated generic prescribing and substitution to improve affordability of medicines.¹² In addition, in order to transform the country to a developed nation by the year 2020, a national blue print of Economic Transformation Program (ETP) was formulated and local generic pharmaceutical industries had been given key priority for boosting the country’s economic transformation.^13,14 However, there are gaps between formulation of these policies and its implementation in Malaysia.^15,16

Despite continuous effort by Malaysian government to increase generic utilization rate in Malaysia, generic medicines only contributed about 40% of the total prescription market.¹⁷ This is indeed low compared to other developed countries like United States and United Kingdom.¹⁸ Misconception and less knowledge of consumers or patients about generic medicines might be one of the factors contributing to this scenario. Consumers are the end users of the pharmaceutical distribution chain and have the ultimate choice to decide whether to consume brand originals or generic medicines. There were two studies conducted previously in Malaysia to investigate Malaysian consumers’ knowledge, attitude, and perception about generic medicines.^19,20 However, the questionnaire used was written in English. Possible difference in language might account for the low understanding of generic medicines in Malaysia. To date, there is only one scale developed by Figueiras et al.²¹ to access patient’s beliefs about generic medicines. Hence, the objective of this study is to translate and validate the generic medicine scale (GMS) among the Malaysian population.

Methods

Translation of the questionnaire

First part: Translation and adaptation process

The GMS was developed by Figueiras et al.²¹ and written permission was obtained from the developers for the translation and validation process. The questionnaire consisted of three sections. First section was the cover letter explaining study background, purpose, procedure of the study. Second section focused about demographic information. The third section comprised the 16-item GMS evaluating patients’ beliefs towards generic medicines in which item number 1 to item number 10 measures patients' beliefs in efficacy and item number 11 to item number 16 measures patients' beliefs in similarity of generic medicines. The responses were framed as a five-point Likert scale (1 = strongly disagree, 2 = disagree, 3 = neutral, 4 = agree and 5 = strongly agree). Translation of questionnaire was performed according to international guidelines for translational studies.^22,23

Step 1: Forward translation: Translation into the target language

Forward translation of the original questionnaires from English to Bahasa Malaysia (BM) was undertaken by two independent qualified linguistic translators (fluent in both BM and English). However, the translators were blinded from each other to produce a translation of the original questionnaire into the target language (i.e. BM).

Step 2: Synthesis of the forward translations

The translated versions were compared with the original versions by researchers regarding discrepancies of words, sentences, and meanings. This process will generate preliminary initial translated version of GMS (PI-TL).

Step 3: Backward translations: Translation back into source language

Backward translation of PI-TL from BM to English was carried out by other two qualified independent translators.

Step 4: Back translation review and consensus meeting

The back-translated versions and PI-TL was compared to evaluate similarity of the instructions, items and response format regarding wording, sentence structure, meaning, and relevance. Continuous discussion sessions were held between the translators and researchers. Inconsistencies and discrepancies were resolved in a consensus meeting and a final version was approved.

Step 5: Cognitive debriefing: Pilot test

The translated questionnaire was then piloted with 33 patients. Their comments on the questionnaires were also taken into consideration which were later discussed and streamlined by the research team. The respondents took 15 min (on average) to complete the questionnaire. Responses of the pilot phase were not included in the final study results. Subsequently, face and content validity of the questionnaire was evaluated by eight postgraduate students who are experts in the field. The final version of the Malaysian GMS was completed and made available for the reliability and validity study. A summary of process of translation and validation process can be found in Figure 1.

Figure 1.

Overview of translation and validation process.

Second part: Patient validation study

Ethics statement

Ethics approval for this study was granted by Malaysia Medical Research and Ethics Committee (NMRR 13-35-14876). Verbal consent was obtained from each patient prior to the study. In addition, the participants were also informed of the research objective, confidentiality of their responses, and their right to withdraw from the study.

Design and setting

Cross-sectional study design was adopted to conduct this study. The study was conducted in Hospital Teluk Intan (HTI), Perak, Malaysia. Hospital Teluk Intan is the third largest hospital in Perak state (548 beds).²⁴ It provides healthcare, emergency treatment for all illness and accidents, primary and advanced medical healthcare. In addition, it is a training hospital that provides training for junior medical doctors and pharmacists.

Sampling and sample size

Patients older than 18 years and literate (i.e. speaking, reading, and writing) with national language of Malaysia (Bahasa Malaysia), were enrolled in the study. Patient with severe health problems of cognitive impairment and caregivers are excluded from the study. A target sample size of 80 patients was estimated to give a good precision for reliability and validity study.²⁵ The number was doubled to increase the reliability of the study outcomes. With expected drop out rate of 20%, convenience sample of 190 patients visiting outpatient pharmacy department was identified between 1 October 2013 and 31 October 2013. In addition, from the current cohort of patients, 37 patients were randomly selected for a 2-week reliability test–retest. However, only 27 patients completed the test–retest after 2-week interval.

Data collection

The questionnaire was self-administered in nature. Questionnaires were distributed by trained pharmacists working at outpatient pharmacy department in Hospital Teluk Intan.

Data analysis

Descriptive statistics were used to describe the demographic characteristics. Internal consistency was assessed by using Cronbach’s alpha. Spearman’s rank correlation was used to assess test–retest reliability. All analyses were performed using SPSS version 16 (SPSS Inc., Chicago, IL). The significance level was set at p < 0.05.

Results

Demographic data

A total of 300 patients were enrolled, but 202 patients provided complete responses with a response rate of 67.3%. Furthermore, for the test–retest analysis, 37 patients were randomly selected and data were available for 27 patients with a response rate of 73.0%. Table 1 describes the patients’ demographic characteristic. Descriptive analysis of GMS is shown in detail in Table 2.

Table 1.

Patients’ demographic characteristic

Demographic characteristic	Total sample, N = 202
Gender
Male	86 (42.6)
Female	112 (55.4)
Missing data	4 (2.0)
Races
Malay	130 (64.0)
Chinese	30 (14.9)
Indian	37 (18.3)
Others	2 (1.0)
Missing data	3 (1.5)
Age
Below 30	53 (26.2)
31–40	36 (17.8)
41–50	47 (23.3)
51–60	33 (16.3)
61 and above	28 (13.9)
Missing data	5 (2.5)
Education level
UPSR (Primary 6)	10 (5.0)
PMR (Secondary 3)	23 (11.4)
SPM/O-level	78 (38.6)
STPM/A-level/Matriculation	11 (5.4)
Diploma	36 (17.8)
Degree	29 (14.4)
Postgraduate	4 (2.0)
Missing data	11 (5.4%)
Monthly salary (MYR)
<RM1000	43 (21.3)
RM1000–RM2000	48 (23.8)
RM2001–RM3000	24 (11.9)
RM3001–RM4000	19 (9.4)
>RM4000	20 (9.9)
Missing data	48 (23.8)

Table 2.

Descriptive analysis of the generic medicine scale (GMS)

Items in questionnaire	n (%)
Items in questionnaire	Strongly disagree	Disagree	Neutral	Agree	Strongly agree	Missing
1. The efficacy of generic medicines is the of brand medicines.	6	40	48	87	21	0
Keberkesanan ubat generik adalah sama seperti ubat berjenama asal.	(3.0)	(19.8)	(23.8)	(43.1)	(10.4)	(0.0)
2. Generic medicines take longer time to be efficacious.	4	47	65	73	11	2
Ubat generik mengambil masa yang lebih lama untuk memberi kesan ubat.	(2.0)	(23.3)	(32.2)	(36.1)	(5.4)	(1.0)
3. Generic medicines are good for less serious diseases.	3	20	44	116	17	2
Ubat generik adalah bagus untuk penyakit yang kurang serius.	(1.5)	(9.9)	(21.8)	(57.4)	(8.4)	(1.0)
4. Treatments with generic medicines take longer.	8	54	63	61	12	4
Rawatan dengan ubat generik mengambil masa yang lebih lama.	(4.0)	(26.7)	(31.2)	(30.2)	(5.9)	(2.0)
5. Generic medicines are made with lower quality substances.	15	74	61	37	10	5
Ubat generik diperbuat daripada bahan yang kurang berkualiti.	(7.4)	(36.6)	(30.2)	(18.3)	(5.0)	(2.5)
6. Generic antibiotics are less efficacious than brand antibiotics.	8	50	57	64	20	3
Antibiotik generik adalah kurang berkesan berbanding dengan antibiotik berjenama asal.	(4.0)	(24.8)	(28.2)	(31.7)	(9.9)	(1.5)
7. Generic medicines have a better quality control than brand medicines.	7	43	71	63	17	1
Ubat generik mempunyai pengawalan kualiti yang lebih ketat berbanding dengan ubat berjenama asal.	(3.5)	(21.3)	(35.1)	(31.2)	(8.4)	(0.5)
8. Generic medicines are cheaper because they are less efficacious.	10	74	49	49	16	4
Ubat generik adalah lebih murah kerana ianya kurang berkesan.	(5.0)	(36.6)	(24.3)	(24.3)	(7.9)	(2.0)
9. Generic medicines have the same effect than brand ones.	3	45	55	88	10	1
Ubat generik mempunyai kesan yang sama seperti ubat berjenama asal.	(1.5)	(22.3)	(27.2)	(43.6)	(5.0)	(0.5)
10. Generic medicines are used for the same illnesses.	2	25	55	101	18	1
Berbanding dengan ubat berjenama asal, ubat generik juga boleh digunakan untuk merawat penyakit yang sama.	(1.0)	(12.4)	(27.2)	(50.0)	(8.9)	(0.5)
11. Generic tablets are the same as brand ones.	5	64	51	65	14	3
Tablet ubat generik adalah sama seperti ubat berjenama asal.	(2.5)	(31.7)	(25.2)	(32.2)	(6.9)	(1.5)
12. Generic medicines have a similar taste as brand medicines.	7	32	59	88	13	3
Ubat generik mempunyai rasa yang hampir sama seperti ubat berjenama asal.	(3.5)	(15.8)	(29.2)	(43.6)	(6.4)	(1.5)
13. Generic medicines have the same side effects as brand medicines.	5	43	60	75	15	4
Ubat generik mempunyai kesan sampingan yang sama seperti ubat berjenama asal.	(2.5)	(21.3)	(29.7)	(37.1)	(7.4)	(2.0)
14. Generic medicines have a different box from brand medicines.	3	23	37	116	23	0
Ubat generik mempunyai bungkusan yang berbeza berbanding dengan ubat berjenama asal.	(1.5)	(11.4)	(18.3)	(57.4)	(11.4)	(0.0)
15. The use of generic medicines is similar to brand ones.	2	20	46	113	20	1
Kegunaan ubat generik adalah sama seperti ubat berjenama asal.	(1.0)	(9.9)	(22.8)	(55.9)	(9.9)	(0.5)
16. Generic medicines are exactly the same as brand medicines.	6	38	57	80	20	1
Secara keseluruhan ubat generik adalah sama seperti ubat berjenama asal.	(3.0)	(18.8)	(28.2)	(39.6)	(9.9)	(0.5)

Beliefs about generic medicines

Participant showed a moderate belief in the efficacy of generic medicines (mean 3.02, SD 0.96, range 1–5) and moderate belief in the similarity of generic medicines mean = 3.39 SD = 0.94, range 1–5).

Validity analysis

Content validity

Content validity of the questionnaire was evaluated by eight postgraduate students who are experts in the field.

Face validity

Initially, the questionnaire, immediately after the translation, was submitted to 33 patients to evaluate whether the instructions, organization, item response and format clarity were clear, understandable, and in a logical order (Step 5 in “Methods” section). The patients in the pilot testing claimed that the statements were clear, easy to understand, and in a logical order.

Reliability analysis

Internal consistency

Cronbach’s alpha test of internal consistency was used for the measurement of reliability. Overall alpha value for the GMS was 0.734 with correlation coefficient ranging from 0.198 to 0.500 (Table 3). Alpha value for efficacy dimension of the scale (i.e. item No.1 to item No. 10) was 0.623 and for similarity dimension (item No.11 to item No. 16) was 0.716. The GMS was declared as a reliable instrument as the Cronbach’s alpha value was within acceptable ranges.^26–28

Table 3.

Reliability analysis of the Malaysia GMS (total correlation and Cronbach’s alpha)

Items in questionnaire	Mean ± SD	Corrected item – Total correlation	Cronbach’s alpha if item is deleted
1. The efficacy of generic medicines is the of brand medicines.	3.38 ± 1.01	0.318	0.723
Keberkesanan ubat generik adalah sama seperti ubat berjenama asal.
2. Generic medicines take longer time to be efficacious.	3.20 ± 0.93	0.301	0.724
Ubat generik mengambil masa yang lebih lama untuk memberi kesan ubat.
3. Generic medicines are good for less serious diseases.	3.62 ± 0.84	0.326	0.722
Ubat generik adalah bagus untuk penyakit yang kurang serius.
4. Treatments with generic medicines take longer.	3.08 ± 0.99	0.250	0.729
Rawatan dengan ubat generik mengambil masa yang lebih lama.
5. Generic medicines are made with lower quality substances.	2.76 ± 1.00	0.272	0.727
Ubat generik diperbuat daripada bahan yang kurang berkualiti.
6. Generic antibiotics are less efficacious than brand antibiotics.	3.19 ± 1.05	0.198	0.736
Antibiotik generik adalah kurang berkesan berbanding dengan antibiotik berjenama asal.
7. Generic medicines have a better quality control than brand medicines.	3.20 ± 0.98	0.291	0.725
Ubat generik mempunyai pengawalan kualiti yang lebih ketat berbanding dengan ubat berjenama asal.
8. Generic medicines are cheaper because they are less efficacious.	2.93 ± 1.07	0.229	0.733
Ubat generik adalah lebih murah kerana ianya kurang berkesan.
9. Generic medicines have the same effect than brand ones.	3.28 ± 0.92	0.435	0.711
Ubat generik mempunyai kesan yang sama seperti ubat berjenama asal.
10. Generic medicines are used for the same illnesses.	3.54 ± 0.86	0.354	0.719
Berbanding dengan ubat berjenama asal, ubat generik juga boleh digunakan untuk merawat penyakit yang sama.
11. Generic tablets are the same as brand ones.	3.10 ± 1.01	0.370	0.717
Tablet ubat generik adalah sama seperti ubat berjenama asal.
12. Generic medicines have a similar taste as brand medicines.	3.34 ± 0.94	0.363	0.718
Ubat generik mempunyai rasa yang hampir sama seperti ubat berjenama asal.
13. Generic medicines have the same side effects as brand medicines.	3.26 ± 0.97	0.376	0.717
Ubat generik mempunyai kesan sampingan yang sama seperti ubat berjenama asal.
14. Generic medicines have a different box from brand medicines.	3.68 ± 0.88	0.294	0.725
Ubat generik mempunyai bungkusan yang berbeza berbanding dengan ubat berjenama asal.
15. The use of generic medicines is similar to brand ones.	3.64 ± 0.83	0.413	0.715
Kegunaan ubat generik adalah sama seperti ubat berjenama asal.
16. Generic medicines are exactly the same as brand medicines.	3.35 ± 0.99	0.500	0.704
Secara keseluruhan ubat generik adalah sama seperti ubat berjenama asal.

Cronbach’s alpha was 0.734 for the total scale with significant intra-class correlation coefficient (p = 0.005).

Test–retest reliability

The test–retest reliability of the 16-item GMS indicates good reliability and stability of the instrument with Spearman’s rank correlation coefficient of 0.532 (r_s = 0.532, n = 202, p = 0.005). Spearman’s rank correlation was used because the data was not normally distributed. This absence of normality was confirmed by Kolmogorov–Smirnov test (p < 0.001 for each of the 16 items).

Discussion

The main objective of this paper was to report the reliability and validity of the translated version of GMS in Malaysian population. This study was the first to systematically translate and validate the 16-item GMS into the Malaysian language. To the best of our knowledge, there are no other studies conducted to translate and validate the GMS. This study reported that Malaysian GMS had good reliability (i.e. both internal consistency and temporal stability).

In terms of validity, content validity is defined as the extent to which a specific set of items reflects a content domain or item sampling adequacy.²⁶ However, unlike domain that is well defined (e.g. knowledge), beliefs about generic medicines is difficult to determine. The common way in evaluating content validity is by expert review for relevance of items to the domain of interest. In this case, content validity was confirmed by expert review of postgraduate students who were expert in generic medicines.

Face validity determine whether the instrument or questionnaire measures the construct of interest.²⁹ It provides insight about how potential respondents might interpret and respond to items.²⁹ In this study, the items in translated GMS statements were clear, easy to understand, and in a logical order. Generally, there are three main types of validity namely, construct, content, and criterion validity.^26,30 The reason construct and criterion validity are not accessed in this case is the lack of “gold standard” in measuring patients’ beliefs about generic medicine. In fact, there is only one GMS developed by Figuerias et al.²¹

Internal consistency reliability indicates how well the groups of test items on a questionnaire fit together conceptually.²⁹ Internal consistency reliability is usually measured by using Cronbach’s alpha coefficient.^31,32 Both the alpha value for efficacy and similarity dimension in the translated GMS was lower compared to the original GMS by Figueiras et al.²¹ (i.e. efficacy dimension, α = 0.623 vs. 0.91; similarity dimension, α = 0.716 vs. 0.80). Possible difference in alpha value might be due to smaller sample size in this study. In fact, the correlation coefficient is affected by sample size.³³ In addition, Cronbach’s alpha coefficient is sample specific. It measures internal consistency for the test response from current respondents.²⁹ Hence, difference in demographic characteristic from two different populations might account for these differences in the alpha values. However, the overall alpha value (i.e. α = 0.734) was acceptable.^26–28 According to Spearman–Brown prophecy formula, alpha value depends on number of items in the scale and the mean inter-item correlations.²⁶ Low value of alpha might be due to a low number of items in the questionnaire or poor interrelatedness between items or heterogeneous constructs.^26,27 In contrast, high value of alpha may indicate that some items are redundant as they are investigating the same question but in a different format.^26,27

For test–retest reliability, the time interval between test and retest should not be too short in order to prevent “learning effect” and should not be too long either because the participants’ scores may have actually changed.²⁵ The longer the time, the lower the reliability measured. Usually, 1 to 2 weeks is recommended.²⁵ The rationale behind reliability analysis is that if a scale or questionnaire truly reflects some meaningful construct, it should assess the same construct comparably on two separate occasions.²⁶ In other words, the effect of the latent variable on observed scores on two or more occasion should be the same.²⁶ The only component that might change across administration of the questionnaire is error.²⁶ As a result of that, the correlation of scores obtained between test and retest to the same individual indicates the stability of the instrument.^26,29 In this study, the test and retest showed large and statistically significant correlation (r_s = 0.532, p = 0.005). A correlation value between 0.5 and 1.0 is large.³⁰ Hence, the translated GMS showed adequate temporal stability. However, like other techniques used for reliability analysis, Spearman correlation was critiqued by other statisticians.^34,35 One of the issues raised was that correlation coefficient cannot assess systematic bias and depends on range of values in the sample.^35,36

Conclusions

The Malaysian version of GMS was proved to be a reliable and valid measure to investigate patients’ belief about generic medicines as it showed acceptable, internal consistency reliability, test–retest reliability, face and content validity.

Footnotes

Funding

This work was supported by the Malaysia National Institutes of Health (NMRR-13-35-14876).

Conflict of interest

None declared.

Author biographies

Zhi Yen Wong is a Pharmacist at Pharmacy Department. Hospital Teluk Intan, Perak, Malaysia. His main research interests are use of generic medicines related to issues in developing countries, health policy, and drug utilization research.

Mohamed Azmi Hassali is an Associate Professor and Deputy Dean (Student Development and Industry & Community Network) at School of Pharmaceutical Sciences, Universiti Sains Malaysia. His main research interests are use of generic medicines related issues in developing countries, health policy, pharmacovigilance, medication adherence and community based health issues research.

Fahad Saleem is a Senior Lecturer at Discipline of Social & Administrative Pharmacy School of Pharmaceutical Sciences, Universiti Sains Malaysia. His main research interests are patient education, medication adherence, health policy, pharmacoepidemiology and community based health issues research.

Abdul Haniff Mohamad Yahaya is a Senior Clinical Pharmacist at Pharmacy Department of Hospital Teluk Intan, Perak, Malaysia. His main research are in pharmacoepidemiology, clinical research, patient safety, health policy and econometrics in health economics.

Hisham Aljadhey is the Vice Dean for Academic Affairs and Director of Medication Safety Research Chair at College of Pharmacy, King Saud University, Riyadh, Saudi Arabia. His main research interests are pharmacoepidemiology and drug safety, rational use of medicines, medication adherence and use of information technology in health care system.

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