HOW TO DIAGNOSE TUBERCULOSIS

According to WHO, 2•9 million people with active, potentially contagious tuberculosis were undiagnosed and likely untreated in 2019. This estimate is supported by national tuberculosis prevalence surveys conducted in Africa and Asia over the last two decades, which revealed significant gaps in tuberculosis detection. Finding the so-called "missing millions" through active tuberculosis case-finding has been advocated due to the potential benefits to individuals through access to treatment, which would reduce morbidity and mortality, and to populations through reduced transmission. and preventing secondary cases.

Active case-finding (ACF) will help minimize avoidable delays in diagnosis and initiation of treatment and will reduce the risk of unfavorable treatment outcomes, health sequelae, and adverse social and economic consequences. Active screening reduces tuberculosis transmission in a home, workplace, school, or another community setting by removing people with active disease and shortening the duration of infectiousness. Policymakers can increase the uptake of TB preventive treatment (TPT) for people who do not have TB disease but are at risk of progression by combining active screening with appropriate diagnostic testing. ACF implementation is costly. However, if carefully planned and implemented, it will be cost-effective and contribute to last-mile efforts to reduce TB incidence.

Mycobacterium Tuberculosis

Active case-finding (ACF) is defined by WHO as systematic screening for active TB, normally outside of health facilities but could also be undertaken at health facilities in a targeted population considered at higher risk of developing TB. The objectives of ACF are (i) targeted case-finding and (ii) prompt initiation of treatment to rapidly cure and render the disease non-infectious.

Active case-finding necessitates systematic screening and clinical evaluation of people who are at high risk of developing tuberculosis, such as contacts of someone who has been diagnosed with tuberculosis or people living with HIV. The Active case-finding aims to diagnose tuberculosis that has been missed by routine practices.  The active case-finding is quite useful in assuming that  

(i)    Groups at high risk for tuberculosis (TB) are clearly defined,

(ii)   Procedures for screening and assessing individuals in these groups are well established, and

(iii)  Health professionals and community workers who should be involved in implementing these procedures are clearly identified.

STRATEGY TO FIND THE MISSING CASES: 

How to Diagnose TB

(i) First, within local health systems with the reinforced capacity to diagnose and treat active tuberculosis. One consistent finding of national tuberculosis surveys over the last two decades is that many people with undiagnosed active tuberculosis sought medical attention but were not diagnosed, or did not seek medical attention due to geographic or financial barriers.

(ii) Second, we suggest an expansion of active case-finding interventions in household contacts, as recommended by WHO. 

A systematic review of studies in low- and middle-income countries found a 4•5 percent prevalence of active tuberculosis among household (or close) contacts. While 51•4 percent of contacts investigated had latent tuberculosis infection. Furthermore, household contacts are easily identified at the time of the index case's diagnosis and are more likely to have an early disease that will progress quickly.

CHALLENGES TO ACF IMPLEMENTATION IN THE FIELD

HOW TO DIAGNOSE TUBERCULOSIS

While it is important to select the algorithms and population groups carefully, there are certain potential pitfalls during implementation. The yield of ACF can be compromised in the following situations:

• Decreased participation of targeted beneficiaries;
• Inappropriate/incomplete assessment of symptoms due to the lack of a standard questionnaire and/or inadequately trained staff;
• Drop-outs during referral for testing and loss to follow up between treatment initiation and completion;
• Inadequate capacity for obtaining a good sample and its appropriate transportation, resulting in a lower yield;
•  Inadequate laboratory techniques, including preparation and reading of the sputum smear or sample handling, may also lead to a lower yield. Quality assurance of laboratory procedures is therefore important;
• Decrease in the overall impact of ACF due to diversion of staff from passive case finding to ACF;
• Delay in treatment initiation leads to poor treatment outcomes of patients found by ACF, which may decrease the cost-effectiveness of ACF