Study population
We conducted a cross sectional study to assess awareness of PAD in adults as part of a prevalence study in Gampaha district, Sri Lanka from 2012 to 2013 [3]. Gampaha is the second most populous district in Sri Lanka, and has 2 million inhabitants. Gampaha district is divided into 13 divisional secretariat areas for administrative purposes. We used a multistage probability proportionate to size sampling technique to recruit 2912 adults aged 40–74 years from 104 clusters in four randomly-selected divisional secretariat areas in Gampaha.
The sample size was determine using the formula for prevalence study described in Lwanga and Lemeshow [12]. Anticipated population prevalence of PAD was assumed to be 3.5 % with 1 % precision required on either side of the proportion. The required sample size was corrected to account for the cluster sampling methodology and for non-response among participants. Thus, the sample size required to detect the expected prevalence in the community with 95 % confidence interval and with 1 % precisionwas 2912.
A cluster was defined as an administrative area of a village officer, and cluster size was 28. The area of a village officer is the smallest administrative unit in Sri Lanka. The age range (40–74 years) was divided into 5-year age groups, and a sample was obtained from each cluster. The number of individuals included in each age group was based on the proportion of the population in each age group in the 2001 national census data. An equal number of males and females were selected for each age group from each cluster. A detail description of the sampling method is published elsewhere [3].
Data collection
The study instrument was an interviewer-administered questionnaire. Questionnaire development was based on several previous studies [6, 7] with the help of an expert panel. Sociodemographic characteristics such as age, sex, level of education, and monthly household income were collected. Age was verified by supportive documents. House to house survey was carried for Data collection. Respondents were interviewed in their own residences including the clinical measurements of ankle brachial pressure index (ABPI) to detect PAD. Arterial Doppler instrument was used to measure the ABPI. For more details, see Weragoda et al. 2015 [3]. Self-reported information on medical history of diabetes mellitus (DM), dyslipidemia, and hypertension was obtained and verified by available clinical records or medications. Information on smoking was also obtained, with exposure categorized according to the classification of the Centers for Disease Control and Prevention in the United States [13]. Assessment of intermittent claudication was based on the Edinburgh Claudication Questionnaire [14].
Participants’ awareness was classified in three groups: “not heard about the disease,” “heard but could not describe the disease,” and “heard about and could describe the disease.” As participants were unfamiliar with the English term PAD, the disease was explained as “blocked or narrowing of arteries of the legs, affecting blood circulation.” Awareness of cerebrovascular accidents (CVA) and myocardial infarction (MI) was assessed in a similar way. CVA was explained as “stroke” (“Anshabhagaya” in the Sinhala language) and MI was explained as “heart attack,” which was the terminology commonly used by the public. Participants who were aware of PAD were asked about common risk factors, possible consequences of untreated PAD, and their sources of information.
The Ethics Review Committee of the Faculty of Medicine, University of Colombo granted approval for the study (Protocol No. EC-12-13). Informed consent was obtained from all participants before participation in the study.
Data analysis
In the analysis, participants who “had not heard about the disease” and ‘heard but could not describe the disease” were combined into one group “not aware” of the disease (PAD, CVA, or MI). Those who had “heard about and could describe the disease” were classified as “aware” of that disease. Participants’ awareness of PAD was compared with awareness of other atherosclerotic diseases (MI and CVA) using paired-samples t-tests. Bivariate analysis for awareness of PAD by selected participant characteristics was performed, and differences between groups were analyzed with Pearson’s chi-square tests. Multivariate logistic regression analysis was used to assess the independent predictors of awareness of PAD. The independent factors included in the model were various sociodemographic measures, presence of PAD risk factors such as DM, hypertension, dyslipidemia, smoking, and the presence of intermittent claudication. We used SPSS Version 16 (SPSS for Windows, Version 16.0. Chicago, SPSS Inc.) for the analyses. Statistical significance was set at p < 0.05.