Globally, Tuberculosis (TB) remains a public health threat despite available vaccines and efficient drugs for treatment. It is the leading cause of morbidity and mortality worldwide [1]. In 2023, TB affected an estimated 10.8 million people and resulted in 1.3 million deaths [1]. Noteworthy is that 90% - 95% of these deaths were found in low and middle-income countries (LMICs) [2][3]. In addition, more than 87% of global TB cases were reported in 30 high-burden countries for TB, including Nigeria [4].

In Africa, TB ranks eighth among the top ten leading causes of death, accounting for 23% of new cases and 31% of TB-related deaths [1]. Nationally, the TB burden is growing along with its population. For example, Nigeria has the sixth-highest TB burden globally, with an estimated 4.3 percent multidrug resistance in new cases [5]. In the country, 268 people die from TB every day [5]. In 2022, annual TB incidence in Plateau State, Nigeria, was estimated at 10,330, but only 3669 were diagnosed and notified, leaving a gap of 6661 undetected TB cases [6].

Studies show that even with newer TB diagnostic tools, up to one-third of people living with TB remain undiagnosed [7][8]. There are also diverse and proven diagnostic options adapted to different settings, but diagnostic gaps persist. It is estimated that 85% - 95% of these deaths could be prevented with early detection, diagnosis, and appropriate treatment. Nevertheless, more than 3 million TB cases are missing annually, and the missed cases are either not diagnosed or diagnosed but not notified [7]. Consequently, the significant risk of transmission is increasing due to the underdiagnosis and under-reporting of TB cases. Of concern is the fact that a person with TB disease can infect 10 to 15 people he or she encounters [9]. This implies that each missed TB case contributes to the current TB burden, thereby compounding the challenge to end TB. Thus, the importance of promptly identifying TB cases and linking them to care cannot be overemphasized.

Low TB case detection remains a major challenge in achieving the End TB targets. The World Health Organization (WHO) emphasized that missed TB cases are a significant contributor to the continual high prevalence and incidence of TB in low and middle-income countries. It then suggested systematic screening of all clients who come to the health facility [10]. Enhanced TB case finding is crucial to achieve the global reduction targets in TB morbidity and mortality as stipulated in the End TB strategy. Active surveillance or screening is defined as all activities conducted by health care workers in the community and facilities to identify previously undetected active cases of TB. New strategies that consider local contexts are needed in countries with high TB burdens like Nigeria. This calls for more sensitive and specific point-of-care diagnostic tests. Active surveillance for TB is currently identified as the best strategy for early diagnosis of TB to curb the spread in communities [11]. Succinctly, active TB screening of hospital attendees and community dwellers is pivotal in finding missing TB cases.

This study assessed the performance of the TB screening and treatment cascade associated with active tuberculosis screening in KNCV-supported sites in Plateau State, drawing on KNCV Nigeria’s experience.

The result summarizes performance across the tuberculosis (TB) screening-to-treatment cascade for a target population for the years 2021 to 2023. It shows how many people were screened, identified as presumptive cases, evaluated, diagnosed, and ultimately started on treatment. Findings show 1,716,744 clients were studied, out of which 1,707,481 clients were screened (99.5%). Clients presumed to have TB were 139,443 (males—72,168; females—67,275), giving an 8.2% yield. All (100%) presumptive TB were further evaluated, of which 7823 (5.6%) were diagnosed as TB positive. TB patients started on treatment were 7514 (96.1%) (Table 1, Table2).

Table 1. TB parameters (Overall).

Table 2. TB parameters (Disaggregated by Gender).

Over the three years, the number of clients screened fluctuated. In 2021, the number screened was 225,8191 for males and 300,514 for females. In 2022, screening slightly increased in both sexes and further increased in 2023, reaching the highest numbers in the period, 268,344 for males and 324,052 females (Table 3 and Figure 1).

The presumptive TB remained low as a proportion of those screened, approximately 14,908 - 28,748 for males and 15,726 - 25,805 for females, disaggregated by age over the years. Except for the year 2021, females consistently showed slightly fewer presumptive cases than males, despite more females being screened than males (Table 3).

Table 3. TB parameters (Disaggregated by Year and Gender).

Figure 1.Distribution of active tuberculosis screening 2021-2023 (absolute count).

The number of presumptive TB further evaluated for TB showed notable progress. 14,908 - 15,726 presumptive TB were reported for the year 2021, in the year 2022, between 25,744 - 28,512 presumptive TB were evaluated, and in the year 2023, between 25,805 - 28,748 presumptive TB were evaluated. Evaluation numbers show an upward trend (Table 3 and Figure 1).

TB case detection was between 691 and 1894, and the yield 3.8% to 9.2%, cases per sex per year. Of the total 7823 TB cases diagnosed, almost all diagnosed were enrolled for treatment, 7514 (96.1%); 4924 males and 2590 females over the three years (Table 3, Figure 2, and Table 1 and Table 2).

Figure 2.Distribution of active tuberculosis screening 2021-2023 (percentage yields).

In conclusion, there was a steady increase in the number of clients tested, presumed TB found, and TB cases diagnosed between 2021 and 2023. Although causality cannot be shown because the study is observational, these changes may be reasonably explained by expanding facility and community-based treatments, staffing support through trained ad hoc personnel, and routine active TB screening (Table 3 and Figure 3).

Figure 3.Trend in active tuberculosis screening 2021-2023.

Over the three years, both the target population and clients screened for TB show noticeable yearly fluctuations by sex disaggregation but generally trending upward. Despite the large numbers screened (99.5%), the number of presumed (8.2%) and diagnosed (5.6%) remains relatively small despite being a targeted screening program. The observed changes are in line with KNCV’s intervention in TB activities over this period in the state. Intervention started about mid-2020, which led to an increase in performance in 2021. The low presumptive and TB yields (8.2% and 5.6%, respectively) could be attributed to reduced ad-hoc staffing strength in 2022, which led to decreases in facility interventions, limiting outreaches to only high-burden LGAs, and contact investigation frequencies. However, in 2023, following ad-hoc staff re-engagement, full contact investigation, and community outreach implementation from January 2023, screening and diagnosis rates rose again. This suggests that improved program reach, consistent program quality, strengthened outreach, improved mobilization, or expanded campaigns are key to success in control of TB. This finding is supported by a previous study in Nigeria, which showed a progressive increase in the number of persons with presumptive TB and those tested following an active search for cases [15].

The presumptive TB remained low as a proportion of those screened. The low presumptive rate is typical in mass screening because most individuals screened are healthy. Females have a larger target population and more screenings. However, males show slightly higher presumptive and diagnosed numbers per population unit screened. The consistently higher male presumptive numbers may reflect higher TB risk among males. This is consistent with global trends of the typical TB pattern that show a higher prevalence of TB among males. Male-to-female differences in presumptive and diagnosed cases might warrant examining risk factors or screening location choices.

Previous studies reported that men bear a disproportionately high burden of disease, face greater barriers to diagnosis and treatment, and may experience worse treatment outcomes than women [16]. The study further averred that the impact of these disparities extends beyond men’s health and that the transmission from affected men is responsible for most new infections in the community. In support of the finding, in 2021, WHO data showed that among adults notified cases of TB, men and women contributed 56.5% and 32.5% respectively [17]. Also, in Nigeria, a study documented that the TB surveillance system screened more women and diagnosed more men with the disease [15]. This is not a surprise because gender disparities in TB are shaped by biological, socio-behavioral, and structural factors and influenced by underlying gender roles and norms. Globally, alcohol use disorders and smoking are more prevalent among men [18][19]. Structural determinants of TB, incarceration, and occupational exposures (e.g., in the mining sector) increase men’s risk of disease.

The number of presumptive TB that had diagnostic evaluation increased significantly from 2021 to 2023, indicating stronger follow-up systems. High evaluation rates suggest efficient programme activities and/or improved follow-up (referral, specimen collection, and diagnostic capacity). TB case detection remained encouraging. Moderate to high detection could reflect high TB prevalence in the screened population. It indicates that more periodic screenings are necessary. Though the yield of TB cases may seem low relative to screening volume. This could mean a true low prevalence of TB among the population screened. It may be a pointer to intensify screening activities with more focus on high-risk settings (e.g., urban slums, mining, prisons).

Treatment initiation closely mirrors the number diagnosed each year. This indicates strong linkage to care, with nearly all diagnosed patients starting treatment. It suggests minimal loss between diagnosis and treatment initiation. This is encouraging and needs to be sustained to achieve set program targets. by the TB control program towards TB elimination.

The efficiency of the combined strategy used in this intervention is affirmed by previous studies. Adding community-based active case finding (ACF) interventions to facility-based services can increase the number of people diagnosed with tuberculosis [20]-[22]. This implies that the “business-as-usual” approach, which is the passive screening, was insufficient in finding missing TB cases and evinced the need for active case finding (ACF), as many people with TB identified in the interventions were previously undiagnosed. This gives credence for the ACF scale-up in the TB control programme [20].

The strength of the intervention is that there was high and improved screening coverage over the years, improved evaluation rates, consistently strong linkage to treatment, and stable detection trends, with no major drops or system failures. Consequently, it implies that the continuum of care (presumptive → evaluated → diagnosed → treated) appears strong.

This study utilized routinely collected program data and may be subject to documentation inaccuracies and possible duplicates. Due to repeated screening contacts, this study may have duplicate counts and documentation errors because it used program data that was routinely collected. Selection bias may have been generated by the exclusion of incomplete records. Furthermore, the lack of a comparison group restricts the attribution of observed benefits to the intervention alone.

Over the course of three years, the program showed remarkable TB screening and treatment cascade performance, with high rates of screening, evaluation, and treatment initiation. Improved TB case detection and care linkage may have resulted from active TB case finding in KNCV-supported locations in Plateau State. Male-to-female disparity might warrant examining risk factors or screening location choices, as well as monitoring gender-specific barriers to early care-seeking. Program efficacy may be enhanced by further bolstering focused screening and community involvement.