Tuberculosis active case-finding: more than just finding cases
Authors: Carole D Mitnick, Courtney M Yuen
Journal: The Lancet Infectious Diseases (2019)

In The Lancet Infectious Diseases, Matthew Saunders and colleagues1Saunders MJ Tovar MA Collier D et al.Active and passive case-finding in tuberculosis-affected households in Peru: a 10-year prospective cohort study.Lancet Infect Dis. 2019; (published online March 22.)http://dx.doi.org/10.1016/S1473-3099(18)30753-9Summary Full Text Full Text PDF PubMed Scopus (31) Google Scholar describe a long-term active case-finding intervention for tuberculosis among households in shanty towns in Callao, Peru. They used home visits over a 10-year period to screen household contacts of an index patient for tuberculosis disease. Although the absolute number of cases found through the active case-finding intervention was modest compared with the number diagnosed by passive case-finding at health facilities, women were preferentially diagnosed through the home visits (36 [68%] of 53 cases diagnosed through active case-finding were female vs 85 [47%] of 179 diagnosed through passive-case-finding; p=0·009). Saunders and colleagues propose that the visits might have overcome a health-care access gap that leads to disproportionate underdetection of tuberculosis among women in this setting. Sparse prevalence survey data from Latin America make it difficult to know whether the case detection gap is truly larger for women in this region, distinct from other parts of the world.2Horton KC MacPherson P Houben RM White RG Corbett EL Sex differences in tuberculosis burden and notifications in low- and middle-income countries: a systematic review and meta-analysis.PLoS Med. 2016; 13: e1002119Crossref PubMed Scopus (179) Google Scholar Regardless, the study by Saunders and colleagues shows that patients found through active case-finding can differ from those who are routinely diagnosed in health facilities. Thus, active case-finding can promote equity through preferential detection of tuberculosis in populations who face barriers to accessing health services.3Stop TB PartnershipData for action for tuberculosis key, vulnerable and underserved populations: working document.http://www.stoptb.org/assets/documents/communities/Data%20for%20Action%20for%20Tuberculosis%20Key,%20Vulnerable%20and%20Underserved%20Populations%20Sept%202017.pdfDate: September, 2017Date accessed: March 4, 2019Google Scholar These vulnerable individuals are probably over-represented among the so-called missing 4 million tuberculosis patients—that is, the gap between the 6 million people diagnosed and 10 million estimated patients with tuberculosis annually.4WHOGlobal tuberculosis report 2018.https://www.who.int/tb/publications/global_report/en/Date: Sept 18, 2018Date accessed: March 4, 2019Google Scholar The study by Saunders and colleagues also emphasises a benefit of active case-finding that is ignored when people focus solely on increasing the numbers of cases detected—namely, the benefit of early diagnosis. The greater proportion of sputum smear-negative cases found through active case-finding in the study (33 [62%] of 53 vs 62 [35%] of 179 found by passive case-finding; p=0·0003) highlights that contact investigations diagnose people earlier, when they are less infectious, thus reducing transmission. However, more sensitive diagnostic technologies—eg, chest radiography5van't Hoog AH Meme HK Laserson KF et al.Screening strategies for tuberculosis prevalence surveys: the value of chest radiography and symptoms.PLoS One. 2012; 7: e38691Crossref PubMed Scopus (78) Google Scholar and molecular testing for Mycobacterium tuberculosis and rifampicin resistance mutations6Steingart KR Schiller I Horne DJ Pai M Boehme CC Dendukuri N Xpert® MTB/RIF assay for pulmonary tuberculosis and rifampicin resistance in adults.Cochrane Database Syst Rev. 2014; 1 (CD009593.)Google Scholar—will be vital if programmes are to maximise the benefits of active case-finding. The study by Saunders and colleagues also highlights the opportunity lost by not giving preventive treatment to adult contacts of tuberculosis patients—a group for whom such treatment is considered optional, according to latest WHO guidance.7WHOLatent tuberculosis infection: updated and consolidated guidelines for programmatic management. World Health Organization, Geneva2018Google Scholar Adult contacts had a substantially increased risk of developing tuberculosis that persisted for 3–4 years. Only a third of contacts who ultimately got sick were diagnosed within a year of the index patient; more cases were diagnosed over the next 3 years. This prolonged increase in risk is similar to that seen in low-incidence countries,8Borgdorff MW Sebek M Geskus RB Kremer K Kalisvaart N van Soolingen D The incubation period distribution of tuberculosis estimated with a molecular epidemiological approach.Int J Epidemiol. 2011; 40: 964-970Crossref PubMed Scopus (71) Google Scholar suggesting that even in this high-burden setting, reactivation rather than reinfection dominates the risk in these initial years. Together, these results support giving preventive treatment to adult household contacts in high-incidence settings. Moreover, household interventions provide a platform for delivering preventive treatment in adults, who are already being assessed as part of contact investigations and whose children or younger siblings might already be receiving preventive treatment. Comprehensive approaches that actively detected, prevented, and treated all forms of tuberculosis were key to pronounced declines in tuberculosis in New York in the 1990s9Frieden TR Fujiwara PI Washko RM Hamburg MA Tuberculosis in New York City: turning the tide.N Engl J Med. 1995; 333: 229-233Crossref PubMed Scopus (629) Google Scholar and in Alaska decades earlier.10Kaplan GJ Fraser RI Comstock GW Tuberculosis in Alaska, 1970: the continued decline of the tuberculosis epidemic.Am Rev Respir Dis. 1972; 105: 920-926PubMed Google Scholar Achieving the Sustainable Development Goal of ending the global tuberculosis epidemic by 2030 will require proactive use of the full arsenal of interventions available today, and rapid integration of innovation, to promptly reach high-risk and vulnerable populations with preventive and curative treatments.11Yuen CM Amanullah F Dharmadhikari A et al.Turning off the tap: stopping tuberculosis transmission through active case-finding and prompt effective treatment.Lancet. 2015; 386: 2334-2343Summary Full Text Full Text PDF PubMed Scopus (99) Google Scholar, 12Keshavjee S Dowdy D Swaminathan S Stopping the body count: a comprehensive approach to move towards zero tuberculosis deaths.Lancet. 2015; 386: e46-e47Summary Full Text Full Text PDF PubMed Scopus (23) Google Scholar Tuberculosis has long been recognised as a disease linked to inequality; active case-finding strategies that promote equity are essential to disrupt that link. CDM and CMY report salary support from a grant from Janssen to Harvard Medical School for work that includes strengthening tuberculosis active case-finding and preventive therapy. Active and passive case-finding in tuberculosis-affected households in Peru: a 10-year prospective cohort studyAlthough active case-finding made an important contribution to tuberculosis detection among contacts, passive case-finding detected most of the tuberculosis burden. Compared with passive case-finding, active case-finding was equitable, helped to diagnose tuberculosis earlier and usually before a positive result on sputum smear microscopy, and showed a high burden of undetected tuberculosis among women. Full-Text PDF Open Access