HLTH 3115 Week 9 Intervention Proposal Example

Chest X-Ray Screening for Tuberculosis Among Adults in Nairobi's Informal Settlements: A Proposal With Its Denominator Attached, a Channel That Reaches It and the Coverage It Must Hit

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Walden University

HLTH 3115: Public and Global Health

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Month Day, Year

Chest X-Ray Screening for Tuberculosis Among Adults in Nairobi's Informal Settlements: A Proposal With Its Denominator Attached, a Channel That Reaches It and the Coverage It Must Hit

The Problem in Population Terms

Kenya's 2016 tuberculosis prevalence survey found pulmonary tuberculosis in 760 per 100,000 urban adults, compared with 453 per 100,000 in rural areas, and in 809 per 100,000 men compared with 359 per 100,000 women (Enos et al., 2018). Nationally, there were about 2.5 people with tuberculosis for every case notified, and the gap was largest among men and adults aged 25 to 34. The usual trigger for testing, a cough lasting beyond two weeks, was present in fewer than half of the survey's cases, whereas nearly nine in ten had X-ray abnormalities. A clinic-based approach that waits for people with a cough to arrive cannot find most of these cases. This proposal sets out a population-level alternative.

The Defined Population

The target population is adults aged 15 and older living in informal settlements in Nairobi County. For planning, this proposal uses a population of 500,000 adults in a defined set of settlements, to be replaced with the exact count from the 2019 census tables for the settlements selected (Kenya National Bureau of Statistics, 2019). Urban informal settlements are chosen because the survey found the highest prevalence in urban areas and among young adult men, groups that are concentrated in these settlements and least likely to be reached by clinic-based testing.

Expected Burden

Each row depends on the one above it. If coverage is low, no improvement in the test can make up for the people who were never screened.

Table 1

Expected Prevalent Cases in the Target Population

Prevalence in informal settlements may be higher than the urban average; the 2016 figure is a conservative planning value. The 85% figure is a planning assumption for the combined chest X-ray and sputum testing pathway.

The Delivery Channel

The channel must reach adults who are not seeking care, including men who work during clinic hours. The proposal uses mobile digital chest X-ray units placed at fixed points within each settlement for two weeks at a time, open in the early morning, evenings and weekends. Kenya's community health workers would visit households beforehand to list adults, explain the screening and invite each person. Chest X-ray is used as the first screen because, in the national survey, X-ray abnormalities flagged far more of the cases than a cough question did (Enos et al., 2018). The World Health Organization's screening guidelines recommend chest X-ray, including with computer-aided detection software, for systematic screening in high-prevalence populations (World Health Organization, 2021). Adults with an abnormal X-ray would give a sputum sample for a rapid molecular test on site, and those who test positive would be linked to treatment at the nearest public facility the same week.

The Coverage Level Required

The proposal must reach enough of the population, often enough, to change something measurable. Evidence on what that means comes from a trial in Vietnam, where adults in 60 communities were offered screening every year for three years. When prevalence was measured in the fourth year, screened communities had 44% less pulmonary tuberculosis than unscreened ones, a prevalence ratio of 0.56 (Marks et al., 2019). That effect came from repeated, community-wide screening, not a single round.

This proposal therefore sets two coverage targets. In each round, at least 60% of listed adults must be screened, including at least 50% of listed men aged 25 to 34. Screening must be repeated annually for at least three years. Below 60%, the program would mainly find people who were already more likely to seek care, and the effect on community prevalence would be too small to detect with a follow-up survey of feasible size. The 50% target for young men is set separately because the national survey showed that this group was both most affected and least likely to be notified.

What Would Change, and How It Would Be Measured

If coverage targets are met, two things should change. In the first year, tuberculosis notifications from the participating settlements should rise sharply, because previously undiagnosed cases are found. Over three years, the prevalence of tuberculosis in the settlements should fall, because finding and treating cases shortens the time people remain infectious. Prevalence would be measured by a survey in the fourth year in screened settlements and in comparable settlements not yet included. If coverage falls below target, the program should not expect a measurable change in prevalence and should report activity, not effect.

Why Not a Clinic-Based Alternative

A clinic-based alternative would strengthen testing for people who come to health facilities with symptoms: better sputum collection, rapid molecular tests and shorter waits. It would be cheaper per person tested and easier to run. But its denominator would be the people who arrive, not the people who live in the settlements. The national survey showed that about two in three people with symptomatic tuberculosis had not sought care, and many people with the disease had no long cough to prompt a visit. A clinic-based plan could improve the care of those who come and still leave most of the disease untouched. That is why this proposal accepts the higher cost of going to the population.

Resources and Risks

The main resources are mobile X-ray units, molecular testing machines, trained radiographers and community health workers' time. The main risks are low turnout among working men, loss of people between a positive test and treatment and stigma. Evening and weekend hours address the first; same-week linkage, tracked by name, addresses the second; and screening everyone, not only people who appear ill, reduces the third.

Conclusion

A clinic-based plan for tuberculosis in Nairobi's informal settlements would serve the people who come to clinics, who are a minority of those with the disease. This proposal attaches a denominator of 500,000 adults, a delivery channel that goes to them and coverage targets of at least 60% of adults each year for three years. Without those numbers, no change in community prevalence should be expected.

References

Enos, M., Sitienei, J., Ong'ang'o, J., Mungai, B., Kamene, M., Wambugu, J., Kipruto, H., Manduku, V., Mburu, J., Nyaboke, D., Ngari, F., Omesa, E., Omale, N., Mwirigi, N., Okallo, G., Njoroge, J., Githiomi, M., Mwangi, M., Kirathe, D., ... Weyenga, H. (2018). Kenya tuberculosis prevalence survey 2016: Challenges and opportunities of ending TB in Kenya. PLoS One, 13(12), Article e0209098. https://doi.org/10.1371/journal.pone.0209098

Kenya National Bureau of Statistics. (2019). 2019 Kenya population and housing census: Volume I. Population by county and sub-county. Kenya National Bureau of Statistics.

Marks, G. B., Nguyen, N. V., Nguyen, P. T. B., Nguyen, T.-A., Nguyen, H. B., Tran, K. H., Nguyen, S. V., Luu, K. B., Tran, D. T. T., Vo, Q. T. N., Le, O. T. T., Nguyen, Y. H., Do, V. Q., Mason, P. H., Nguyen, V.-A. T., Ho, J., Sintchenko, V., Nguyen, L. N., Britton, W. J., & Fox, G. J. (2019). Community-wide screening for tuberculosis in a high-prevalence setting. New England Journal of Medicine, 381(14), 1347-1357. https://doi.org/10.1056/NEJMoa1902129

World Health Organization. (2021). WHO consolidated guidelines on tuberculosis: Module 2: Screening: Systematic screening for tuberculosis disease. World Health Organization. https://www.who.int/publications/i/item/9789240022676