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The following is a summary of “Genotyped cluster investigations versus standard contact tracing: comparative impact on latent tuberculosis infection cascade of care in a low-incidence region,” published in the January 2025 issue of Infectious Disease by Asare-Baah et al. 

Cluster and contact investigations seek to recognize and treat individuals with tuberculosis (TB) and latent TB infection (LTBI), but while genotyped cluster investigations may identify more epidemiological links than contact investigations, which might not always lead to a reduced infection.  

Researchers conducted a retrospective study to assess the impact of genotyped cluster investigations vs standard contact investigations on the LTBI care cascade in a low-incidence setting.  

They performed a matched case-control study within a cohort of 6,921 TB cases from Florida (2009–2023). Cases (n=670) underwent genotyped cluster investigations, while controls (n=670) received standard contact investigations and were matched 1:1 by age. Outcomes of the LTBI care cascade were compared using Pearson’s chi-square tests.  

The results showed that of 5,767 identified contacts, 3,230 (56.0%) were in the case group and 2,537 (44.0%) in the control group. A higher proportion of contacts were evaluated in the control group (85.5%) than in the case group (81.5%, P <0.001). The proportion of evaluated contacts diagnosed with LTBI was similar between the groups (case: 20.4%, control: 21.5%, P=0.088), but a greater percentage in the control group initiated TB preventive treatment (TPT) (95.9% vs 92.9%, P =0.029). TPT completion rates were similar (case: 65.2%, control: 66.3%, P =0.055). The TB cases in the case group were more likely to be male, U.S.-born, Asian, residents of long-term care or correctional facilities, and have histories of alcohol use, homelessness, and drug use in the past year.  

Investigators concluded that despite demographic and epidemiological differences, cluster investigations identified more contacts and had no significant impact on LTBI diagnoses but were less effective than standard contact investigations in evaluating contacts, initiating treatment, and ensuring completion. 

Source: bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-024-10358-4