This survey was designed to obtain national estimates on the burden of rheumatic disorders through a household level survey. Adults aged 18 years or more comprised the study population. [24].
Sample size and sampling:
Assuming a point prevalence of rheumatological disorders among Bangladeshi adults of 24% [19], at 5% precision level, 280 participants were required in each reporting domain. Considering four reporting domains (rural-urban, male-female), a design effect of 1.5, and a 85% response rate, the calculated sample size for the national level was 1,978. This was finally rounded to 2,000.
The primary sampling units (PSUs) in Bangladesh constitute the sampling frame of national or subnational surveys. We used the PSUs of 2001 Census stratified in to the then seven divisions and rural and urban areas [25]. These were Mauza and Mahalla in rural and urban areas respectively. Total and urban rural population of the division were considered for allocating number of PSUs. Finally, 20 PSUs (8 urban and 12 rural) were selected and 100 households were included from each PSU. In each PSU, 100 consecutive households were selected starting from the first household in the map. Households having even and odd numbers were assigned as male and female households to recruit one men and one women, respectively, using the Kish table [26].
Field team and its training:
Each team consisted of one research physician, one field organizer and two interviewers. The research physicians having at least one-year residency in rheumatology were selected. The field team underwent a three-day long training in Bangabandhu Sheikh Mujib Medical University (BSMMU). All investigators and WHO technical team coordinated and conducted the training using a manual specially prepared for this survey. All investigators were present at the training sessions to ensure uniform understanding of procedures. A dry run of the procedure was then performed.
Survey instrument and data collection:
The survey instrument was the modified COPCORD questionnaire [27]. The first part of the questionnaire aimed at detection of the respondents with musculoskeletal pain with some elaboration of the complaints, second part was a structured history and examination sheet (COPCORD examination sheet) used by the research physicians for the diagnosis of disorders and detection of disability. The English version of the first part of the questionnaire was translated to Bangla, then adapted and validated as per standard procedure [28].
Field work:
Data were collected in each PSU over a period of six days with engagement of the local community and health authority. The field organizer visited in advance and started household listing with the help of local health assistant on the first day. The field interviewers collected data, identified screening positive respondents, took physical measurements, and arranged interview with the research physician during remaining five days using the household listing prepared. The research physician interviewed and examined the positive respondents for making a diagnosis. In doubtful cases, opinion of a rheumatologist from divisional level medical college was sought. At least one such visit was ensured for each PSU for validation of diagnosis. Erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor and anti-citrullinated peptide antibody were tested in a pre-selected laboratory located nearby to aid diagnosis.
Operational definitions:
Positive respondent:
A subject was considered a positive respondent if he/she reported occurrence of pain at muscles, bones, joints, or any part of the body (musculoskeletal symptom) during the preceding seven days. The respondents in whom musculoskeletal pain appeared, developed, or disappeared in the preceding seven days were also labeled as a positive respondent.
Rheumatic disorders:
All positive respondents were interviewed and thoroughly examined by the research physicians. Internationally accepted criteria [29-33] were used with adaptations whenever necessary. For conditions with no internationally accepted criteria and epidemiological definition, the clinical judgment of the research physician was used. Difficult cases, if any, were reviewed by the investigators (expert rheumatologist) during their routine visit to PSUs.
Disability and work loss:
Disability was scored with a validated Bangla version of the Health Assessment Questionnaire (B-HAQ) [34]. This tool assesses the subjects’ level of functional ability and included questions of fine movements of the upper extremity, locomotor activities of the lower extremity, and activities that involve extremities. The B-HAQ included 20 items referring to basic activities of daily living, grouped into eight categories of functioning, viz., dressing and grooming, arising, eating, walking, hygiene, reach, grip and activities. Each category contained at least two specific component questions. Respondents are asked to rate the degree of difficulty they experienced in carrying out each activity on a 4-point rating scale: 0 (without any difficulty), 1 (with some difficulty), 2 (with much difficulty), and 3 (unable to do). The highest response in each category was divided by 8, yielding a total disability score of 0–3, where zero is no disability and 3 is severe disability [35] Work loss was defined as duration of temporary cessation of work due to musculoskeletal pain or disability in preceding 12 month.
Statistical analysis:
The data were entered into Excel spreadsheet and transferred to EpiInfo (version 7) for analysis. Missing values were identified to confirm the denominators, consistency and distribution of quantitative data for normality were checked.
Economic status was assessed by constructing the wealth index using principal component analysis of ownership of 20 household asset items [24]. The sample was then divided into quartile from one (lowest) to four (highest).
All quantitative variables such as age, years of education, body mass index (BMI), B-HAQ score were categorized before analysis. Alfa was set at 5% for considering significance. Therefore 95% confidence intervals were calculated for all percent estimates such as rheumatic disorders, disabilities and related work loss. Results were presented for four reporting domains: rural, urban, residential locations and sex groups. Multiple logistic regression analysis was done to obtain adjusted odds ratios and their 95% confidence intervals of rheumatological disorders combined. All potential candidate variables were entered simultaneously into the logistic model. Disability was defined as B-HAQ score of 0.8 or more [36].
ETHICS APPROVAL AND CONSENT TO PARTICIPATE
Ethical guidelines as outlined by the Declaration of Helsinki were followed throughout the study. Ethical clearance was obtained from the Institutional Review Board of BSMMU. Concurrence has been obtained from the local health authorities and elected representatives of the local government prior to data collection. Written (or thumb impression if unable to write) consent was obtained from the respondents in Bangla as per BSMMU Institutional Review Board (IRB) guidelines.