Risk factors associated with large clusters of tuberculosis patients determined by whole-genome sequencing in a high-tuberculosis-burden country.

Whole-genome sequencing (WGS) analysis has great discriminative power for detecting similar molecular fingerprints of suspected tuberculosis (TB) clusters. The proportion of TB cases within clusters and the associated risk factors are important epidemiological parameters guiding appropriate outbreak control strategies in endemic settings. We conducted a hospital-based TB case-cohort study between 2003 and 2011 in the northernmost province of Thailand. We identified TB clusters by Mycobacterium tuberculosis WGS and analysed the risks of TB clustering and the characteristics of large clusters compared with small clusters. Among 1146 TB isolates, we identified 77 clusters with 251 isolates defined by a 5-single-nucleotide variant (SNV) cutoff and 112 clusters with 431 isolates defined by a 12-SNV cutoff. Twelve large clusters with 6 isolates or more in each cluster were identified by a 12-SNV cutoff. Sublineage 2.2.1 (both Ancestral and Modern) strains and imprisonment were independently associated with large clusters. Furthermore, although large clusters of Lineage 2.2.1/Ancestral strains included a high number of prisoners, Lineage 2.2.1/Modern strain clusters were only associated with treatment failures and drug resistance. Heterogeneity among lineage strains was observed with respect to large-cluster characteristics. Patients with an increased TB-transmission tendency should be priority targets for contact investigations and outbreak interventions to prevent ongoing transmission.

Contact tracing for tuberculosis, Thailand.

PROBLEM: Despite implementation of universal health coverage in Thailand, gaps remain in the system for screening contacts of tuberculosis patients. APPROACH: We designed broader criteria for contact investigation and new screening practices and assessed the approach in a programme-based operational research study in 2017-2018. Clinic staff interviewed 100 index patients and asked them to give household and non-household contacts an invitation for a free screening and chest X-ray. Contact persons who attended received 250 Thai baht (about 8 United States dollars) allowance for transport. LOCAL SETTING: Chiang Rai province, Thailand, has high rates of tuberculosis notification and a high number of people living in poverty. The coverage of contact investigation in under 5-year-olds was only 33.2% (222 screened out of 668 contacts) over 2011-2015. RELEVANT CHANGES: Index patients identified 440 contacts in total and gave invitation cards to 227 of them. The contact investigation coverage was 81.1% (184/227) and tuberculosis detection among contacts screened was 6.0% (11/184). Of the 11 contacts with active tuberculosis, three did not have tuberculosis symptoms, three were non-household contacts and three were contacts of non-smear-positive tuberculosis patients. The contact investigation coverage of the contacts younger than 5 years was 100% (14/14) and the yield of tuberculosis detection in this age group was 21.4% (3/14). LESSONS LEARNT: High coverage of contact investigation with a high yield of tuberculosis detection among contacts can be achieved by applying broader criteria for contact investigation and providing financial support for transportation.

High tuberculosis burden among HIV-infected populations in Thailand due to a low-sensitivity tuberculin skin test.

The current Thai guideline recommends that among people living with HIV, isoniazid preventive therapy (IPT) should be given to those with a positive tuberculin skin test (TST). We conducted a case-control study, nested within a cohort study, in Chiang Rai Province in Thailand to determine the role of TST in predicting the development of active tuberculosis (TB) within the following 2 years. Comparison between participants with CD4+ counts <50cells/mm3 to those with CD4+ ≥200cells/mm3 revealed that TST results were less sensitive (7.7% vs 50.0%) and had a lower negative predictive value (73.1% vs 97.3%) in those with a CD4+ count <50cells/mm3. In people with HIV, using a positive TST result as a criterion for initiating IPT inadvertently decreases the benefits of IPT, especially among those with low CD4+ counts.

Ensuring tuberculosis treatment adherence with a mobile-based CARE-call system in Thailand: a pilot study.

Background: Medication non-adherence in tuberculosis (TB) patients is an obstacle to TB treatment. Directly observed treatment to monitor and ensure adherence still has some limitations in high TB-burden countries. Most digital adherence technologies emphasize medication-taking reminder functions; however, a bi-directional communication platform to provide patient-health workers with an interface that focuses on enhancing medication adherence is likely to improve medical adherence. A budgeted mobile-based system called CARE-call providing both functions was developed and evaluated concerning whether it could enhance medication adherence.Design: Mixed methods combined quantitative and qualitative approaches. One hundred TB patients were randomized into intervention or control groups. Medication adherence rates between the two groups were compared. A focus group discussion was conducted to obtain in-depth perspectives from the patients.Results: At a 90% adherence level, the number of non-adherence patients in the intervention group was significantly lower than that of the control group (7.5% vs. 27.5%, p= .037). The participants were satisfied with the functions provided by the system, especially the confidentiality of the monitoring process, which did not involve monitoring by imaging or video recording. The bi-directional communication enabled them to contact health staff when concerns arose during the treatment course. Poor mobile phone signals and fast battery drain were reported as major technical problems of the system.Conclusions: The CARE-call system was able to prevent non-adherence in this rural setting in Thailand. However, further investigation with a larger sample size should be conducted on whether the system can also improve successful TB treatment outcome.

Predicting the risk of pulmonary tuberculosis based on the neutrophil-to-lymphocyte ratio at TB screening in HIV-infected individuals.

BACKGROUND: The neutrophil to lymphocyte ratio (NL ratio) has been reported to be a predictive biomarker of tuberculosis (TB). We assessed the association between the NL ratio and the incidence of active TB cases within 1 year after TB screening among HIV-infected individuals in Thailand. METHODS: A day care center that supports HIV-infected individuals in northernmost Thailand performed TB screening and follow-up visits. We compared the baseline characteristics between the TB screening positive group and the TB screening negative group. The threshold value of NL ratio was determined by cubic-spline curves and NL ratios were categorized as high or low NL ratio. We assessed the association between NL ratio and progression to active TB within 1-year using the Cox-proportional hazard model. RESULTS: Of the 1064 HIV-infected individuals who screened negative for TB at baseline, 5.6% (N = 60) eventually developed TB and 26 died after TB diagnosis. A high NL ratio was associated with a higher risk of TB (adjusted hazard ratio (aHR) 2.19, 95% CI: 1.23-3.90), after adjusting for age, sex, ethnicity, CD4 counts, and other risk factors. A high NL ratio in HIV-infected individuals with normal chest X-ray predicted TB development risk. In particular, a high NL ratio with TB symptoms could predict the highest risk of TB development (aHR 2.58, 95%CI: 1.07-6.23). CONCLUSIONS: Our results showed that high NL ratio increased the risk of TB. NL ratio combined with TB symptoms could increase the accuracy of TB screening among HIV-infected individuals.