The methodology section includes the sampling strategy, data collection, study instruments, the analysis plan, and ethical considerations.
Sampling strategy
This is a cross-sectional study; implemented in eleven provinces of Afghanistan. The geographic and demographic representativeness determined the choice of provinces. The selected provinces comprised Kabul, Herat, Nangarhar, Kandahar, Balkh, Badakhshan, Bamyan, Farah, Khost, Kunar, and Samangan. Traditionally, Afghanistan is divided into different demographic and geographical zones ( south, southeast, southwest, east, west, north, northeast, and central), selected provinces represent different zones.
As all PHC facilities in studied provinces equated to 870, therefore, considering a 95% confidence interval, a sample size of 161 facilities established the sample frame. A stratified sampling strategy facilitated the selection of sampled facilities within different categories from an inclusive list of facilities.
Each category of health facilities in the list was deliberated as a stratum. The categories contained District Hospital (DH), Comprehensive Health Center (CHC), Basic Health Center (BHC), Sub Health Center (SHC), and Mobile Health Team (MHT). The number of sampled facilities in each stratum was proportionate to the number of all health facilities in that stratum. The stratum specific sample sizes were determined using following equation: nh = (NH / N) * n
Equation 1 Stratified sampling
Where “nh” is the sample size of the stratum. “Nh” is the population size of the stratum. “N” is the total population size and “n” is the total sample size.
Data collection, monitoring, and supervision
We trained provincial NTP officers to collect the data. We also prepared the national NTP officers to undertake supervisions in assigned provinces during the data collection phase. The national TB officers provided technical support to enumerators and verified the sites, the enumerators had visited.
We utilized the following tools for data collections:
Observation checklist
The observation checklist included managerial, administrative, patient management, physical environment, and case finding sections.
Interview instruments
The semi-structured tool included questions on active case finding strategies, guidelines, checklists, and indicators.
Data management and quality assurance
We employed a five-step approach to ensure the quality of the study data. We primarily designed the study tools with complementarity in mind, we strategized to have some core similar questions to ask from different respondents to enable triangulation, secondly, we required all enumerators to get filled questionnaires and observation checklists signed by health facility managers, thirdly, we called different facilities to verify enumerators had visited intended facilities, fourthly, we patterned all filled questionnaires for completeness and accuracy, finally, we crossed matched the entered data with hard copies. Additionally, we integrated the following measures in all phases of this study.
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Deploying the high-quality study team.
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Training of provincial NTP officers for data collection as they were acquainted with the work.
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Enabling national NTP officers to supervise the data collection process at the provincial and health facility level.
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Translating study tools to local languages. The translated tools were retranslated to English by a third party to ensure the integrity of questions and concepts.
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Training of enumerators
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The pilot of study instruments
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The entry of collected data into password protect databases with established rules to limit the volume of missed data.
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Extensive monitoring and supervision of data collection, entry, and analysis.
Data analysis
The sensitivity of surveillance and information system to detect TB cases
We calculated the proportion of TB cases detected by the TB surveillance system and the proportion of those cases in the community. To calculate the sensitivity, we used the health events by the gold standards table (CDC, 2016). In principle, gold standards are regarded as the best screening tests or procedures under reasonable conditions. Here, we measure the accuracy of TB surveillance in Afghanistan by comparing it against the gold standard test in a 2 × 2 table to calculate its sensitivity and precision. CDC updated surveillance evaluation guideline also uses a 2 × 2 Table 1 to measure surveillance system sensitivity.
Table 1
2 × 2 tables of calculating sensitivity
| Health events by gold standards | |
Detected by surveillance | | Yes | No | |
Yes | A (True positive) | B (False positive) | A + B |
No | C ( False negative) | D ( True negative) | C + D |
| A + C | B + D | |
Table 2
Primary health care system sensitivity to detect TB cases (There is a limitation that province-specific TB prevalence is not available).
Provinces | Provincial Population (2015–2016) | TB prevalence rate per 100000 | Estimated number of TB cases in each province | All TB positive cases from the annual report on cases registration NTP, 2016 | The sensitivity of the primary health care system detected TB cases |
Kabul | 4,372,977 | 340 | 14868 | 6108 | 41.08% |
Herat | 1,890,202 | 340 | 6427 | 3194 | 49.70% |
Nanrhar | 1,517,388 | 340 | 5159 | 4530 | 87.81% |
Balkh | 1,325,659 | 340 | 4507 | 2169 | 48.12% |
Kandahar | 1,226,593 | 340 | 4170 | 2626 | 62.97% |
Badakhsh | 950,953 | 340 | 3233 | 1076 | 33.28% |
Khost | 574,582 | 340 | 1954 | 1985 | 101.61% |
Kunar | 450,652 | 340 | 1532 | 1184 | 77.27% |
Bamyan | 447,218 | 340 | 1521 | 455 | 29.92% |
Samangan | 387,928 | 340 | 1319 | 581 | 44.05% |
Farah | 507,405 | 340 | 1725 | 750 | 43.47% |
Total | 13,651,557 | 340 | 46415 | 24658 | 56.30% |
Ethical Consideration
The study received ethical approval from MoPH’s Institutional Review Board (IRB). All participants provided informed consent before participating in the study. For patients, the interviewers read the informed consent and described the objectives, benefits, voluntary participation, confidentiality, and rights of respondents’ withdrawal. The enumerators had also got trained on local cultural norms and socially acceptable conduct.
Objectives
The current study has the following specific objectives:
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To examine the different dimensions of the surveillance system for TB in Afghanistan.
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To evaluate the level of PHC facilities involvement in TB active case findings per BPHS requirements.