Evaluation of tuberculosis contact investigations in Japan

Contact investigation of tuberculosis in Shanghai, China: A 13-year cohort

OBJECTIVES

Tuberculosis (TB) contact investigation is an effective strategy for TB control. We established a close-contact cohort to evaluate the effect of contact investigation in Shanghai, China.

METHODS

Close contacts of bacteria-positive TB cases diagnosed from 2009 to 2018 in the Songjiang District of Shanghai were screened and followed up until 2021 through symptom examination or other alternatives, and the incidence and risk factors for developing active TB among close contacts were assessed by survival analysis and WGS.

RESULTS

7018 close contacts of 2861 bacteria-positive TB cases were investigated. The median follow-up time was 7.4 years. 97 close contacts (185/100,000, 95%CI: 151-226) developed TB. Survival analysis showed that index cases who were in younger age groups, living in urban settings, smear-positive, and reported a healthcare-seeking delay for TB had higher risks of generating contact cases. Close contacts with matched strains developed TB at an average of 26.5 months based on WGS.

CONCLUSION

A 2-year ideally longer follow-up for close contacts would be beneficial. To improve early case detection, more attention needs to be paid to those contacts whose index cases were living in urban settings, were smear-positive, had a healthcare-seeking delay for TB, and/or were aged ≤18 years.

High proportion of tuberculosis transmission among social contacts in rural China: a 12-year prospective population-based genomic epidemiological study

Tuberculosis (TB) is more prevalent in rural than urban areas in China, and delineating TB transmission patterns in rural populations could improve TB control. We conducted a prospective population-based study of culture-positive pulmonary TB patients diagnosed between July 1, 2009 and December 31, 2020 in two rural counties in China. Genomic clusters were defined with a threshold distance of 12-single-nucleotide-polymorphisms, based on whole-genome sequencing. Risk factors for clustering were identified by logistic regression. Transmission links were sought through epidemiological investigation of genomic-clustered patients. Of 1517 and 751 culture-positive pulmonary TB patients in Wusheng and Wuchang counties, respectively, 1289 and 699 strains were sequenced. Overall, 624 (31.4%, 624/1988) patients were grouped into 225 genomic clusters. Epidemiological links were confirmed in 41.8% (196/469) of clustered isolates, including family (32.7%, 64/196) and social contacts (67.3%, 132/196). Social contacts were generally with relatives, within the community or in shared aggregated settings outside the community, but the proportion of clustered contacts in each category differed between the two sites. The time interval between diagnosis of student cases and contacts was significantly shorter than family and social contacts, probably due to enhanced student contact screening. Transmission of multidrug-resistant (MDR) strains was likely responsible for 81.4% (83/102) of MDR-TB cases, with minimal acquisition of additional resistance mutations. A large proportion of TB transmission in rural China occurred among social contacts, suggesting that active screening and aggressive contact tracing could benefit TB control, but contact screening should be tailored to local patterns of social interactions.

Screening tests for active pulmonary tuberculosis in children

BACKGROUND

Globally, children under 15 years represent approximately 12% of new tuberculosis cases, but 16% of the estimated 1.4 million deaths. This higher share of mortality highlights the urgent need to develop strategies to improve case detection in this age group and identify children without tuberculosis disease who should be considered for tuberculosis preventive treatment. One such strategy is systematic screening for tuberculosis in high-risk groups.

OBJECTIVES

To estimate the sensitivity and specificity of the presence of one or more tuberculosis symptoms, or symptom combinations; chest radiography (CXR); Xpert MTB/RIF; Xpert Ultra; and combinations of these as screening tests for detecting active pulmonary childhood tuberculosis in the following groups. - Tuberculosis contacts, including household contacts, school contacts, and other close contacts of a person with infectious tuberculosis. - Children living with HIV. - Children with pneumonia. - Other risk groups (e.g. children with a history of previous tuberculosis, malnourished children). - Children in the general population in high tuberculosis burden settings.

SEARCH METHODS

We searched six databases, including the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase, on 14 February 2020 without language restrictions and contacted researchers in the field.

SELECTION CRITERIA

Cross-sectional and cohort studies where at least 75% of children were aged under 15 years. Studies were eligible if conducted for screening rather than diagnosing tuberculosis. Reference standards were microbiological (MRS) and composite reference standard (CRS), which may incorporate symptoms and CXR.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed study quality using QUADAS-2. We consolidated symptom screens across included studies into groups that used similar combinations of symptoms as follows: one or more of cough, fever, or poor weight gain and one or more of cough, fever, or decreased playfulness. For combination of symptoms, a positive screen was the presence of one or more than one symptom. We used a bivariate model to estimate pooled sensitivity and specificity with 95% confidence intervals (CIs) and performed analyses separately by reference standard. We assessed certainty of evidence using GRADE.

MAIN RESULTS

Nineteen studies assessed the following screens: one symptom (15 studies, 10,097 participants); combinations of symptoms (12 studies, 29,889 participants); CXR (10 studies, 7146 participants); and Xpert MTB/RIF (2 studies, 787 participants). Several studies assessed more than one screening test. No studies assessed Xpert Ultra. For 16 studies (84%), risk of bias for the reference standard domain was unclear owing to concern about incorporation bias. Across other quality domains, risk of bias was generally low. Symptom screen (verified by CRS) One or more of cough, fever, or poor weight gain in tuberculosis contacts (4 studies, tuberculosis prevalence 2% to 13%): pooled sensitivity was 89% (95% CI 52% to 98%; 113 participants; low-certainty evidence) and pooled specificity was 69% (95% CI 51% to 83%; 2582 participants; low-certainty evidence). Of 1000 children where 50 have pulmonary tuberculosis, 339 would be screen-positive, of whom 294 (87%) would not have pulmonary tuberculosis (false positives); 661 would be screen-negative, of whom five (1%) would have pulmonary tuberculosis (false negatives). One or more of cough, fever, or decreased playfulness in children aged under five years, inpatient or outpatient (3 studies, tuberculosis prevalence 3% to 13%): sensitivity ranged from 64% to 76% (106 participants; moderate-certainty evidence) and specificity from 37% to 77% (2339 participants; low-certainty evidence). Of 1000 children where 50 have pulmonary tuberculosis, 251 to 636 would be screen-positive, of whom 219 to 598 (87% to 94%) would not have pulmonary tuberculosis; 364 to 749 would be screen-negative, of whom 12 to 18 (2% to 3%) would have pulmonary tuberculosis. One or more of cough, fever, poor weight gain, or tuberculosis close contact (World Health Organization four-symptom screen) in children living with HIV, outpatient (2 studies, tuberculosis prevalence 3% and 8%): pooled sensitivity was 61% (95% CI 58% to 64%; 1219 screens; moderate-certainty evidence) and pooled specificity was 94% (95% CI 86% to 98%; 201,916 screens; low-certainty evidence). Of 1000 symptom screens where 50 of the screens are on children with pulmonary tuberculosis, 88 would be screen-positive, of which 57 (65%) would be on children who do not have pulmonary tuberculosis; 912 would be screen-negative, of which 19 (2%) would be on children who have pulmonary tuberculosis. CXR (verified by CRS) CXR with any abnormality in tuberculosis contacts (8 studies, tuberculosis prevalence 2% to 25%): pooled sensitivity was 87% (95% CI 75% to 93%; 232 participants; low-certainty evidence) and pooled specificity was 99% (95% CI 68% to 100%; 3281 participants; low-certainty evidence). Of 1000 children, where 50 have pulmonary tuberculosis, 63 would be screen-positive, of whom 19 (30%) would not have pulmonary tuberculosis; 937 would be screen-negative, of whom 6 (1%) would have pulmonary tuberculosis. Xpert MTB/RIF (verified by MRS) Xpert MTB/RIF, inpatient or outpatient (2 studies, tuberculosis prevalence 1% and 4%): sensitivity was 43% and 100% (16 participants; very low-certainty evidence) and specificity was 99% and 100% (771 participants; moderate-certainty evidence). Of 1000 children, where 50 have pulmonary tuberculosis, 31 to 69 would be Xpert MTB/RIF-positive, of whom 9 to 19 (28% to 29%) would not have pulmonary tuberculosis; 969 to 931 would be Xpert MTB/RIF-negative, of whom 0 to 28 (0% to 3%) would have tuberculosis. Studies often assessed more symptoms than those included in the index test and symptom definitions varied. These differences complicated data aggregation and may have influenced accuracy estimates. Both symptoms and CXR formed part of the CRS (incorporation bias), which may have led to overestimation of sensitivity and specificity.

AUTHORS' CONCLUSIONS

We found that in children who are tuberculosis contacts or living with HIV, screening tests using symptoms or CXR may be useful, but our review is limited by design issues with the index test and incorporation bias in the reference standard. For Xpert MTB/RIF, we found insufficient evidence regarding screening accuracy. Prospective evaluations of screening tests for tuberculosis in children will help clarify their use. In the meantime, screening strategies need to be pragmatic to address the persistent gaps in prevention and case detection that exist in resource-limited settings.

High incidence and low case detection rate among contacts of tuberculosis cases in Shanghai, China

Background

To assess the effect of a contact investigation strategy by assessing the incidence of tuberculosis and the case detection rate among contacts of tuberculosis patients.

Methods

The pulmonary tuberculosis incidence among contacts was determined retrospectively from a tuberculosis information management system. For each detection method (symptom examination only, symptom examination plus chest radiography or other alternatives), the detection rate of pulmonary tuberculosis patients among contacts was derived from contact investigation form records.

Results

Sixty-nine cases of pulmonary tuberculosis were identified among a total of 8137 contacts after an average follow-up of 2.6 years (range: 0.25–5.25) during the period from 2010 to 2014. The incidence density was 329/100,000 person-years (PYs), and the 95% confidence interval (CI) was 256–419/100,000 PYs, which was significantly higher than the notification rate during the same period in the general population (29–30/100,000 PYs). The incidence density was higher (p < 0.0001) among male contacts (462/100,000 PYs) than among female contacts (236/100,000 PYs). The incidence density did not differ (p > 0.05) between contacts whose index case was sputum smear positive and those whose index case was sputum smear negative. Contacts who were biologically related family of the index cases exhibited a higher (p < 0.05) incidence density (475/100,000 PYs) than other contacts (281/100,000 PYs). Fifteen of the 69 incident cases were found through contact investigation, corresponding to a case detection rate via contact investigation of 22% (95% CI: 13–33%). The relevance ratio was 288/100,000 (12/4163) by both chest radiography and symptom survey, which was significantly higher than the rate detected by symptom survey alone, of 57/100,000 (2/3486), p = 0.028. The cumulative incidence in the contacts was 761/100,000 (62/8137) within 3 years from the time that the index cases were diagnosed with pulmonary tuberculosis, which was higher than the incidence rate of 210/100,000 (7/3328) recorded after 3 years (p < 0.001).

Conclusions

The contacts were at higher risk of pulmonary tuberculosis than the general population; however, only approximately 22% of the incident cases could be detected through contact investigation. Therefore, the contact investigation strategy must be improved for better detection of potential pulmonary tuberculosis cases.

Trends in incidence and mortality of tuberculosis in Japan: a population-based study, 1997-2016

Japan is still a medium-burden tuberculosis (TB) country. We aimed to examine trends in newly notified active TB incidence and TB-related mortality in the last two decades in Japan. This is a population-based study using Japanese Vital Statistics and Japan Tuberculosis Surveillance from 1997 to 2016. We determined active TB incidence and mortality rates (per 100 000 population) by sex, age and disease categories. Joinpoint regression was applied to calculate the annual percentage change (APC) in age-adjusted mortality rates and to identify the years showing significant trend changes. Crude and age-adjusted incidence rates reduced from 33.9 to 13.9 and 37.3 to 11.3 per 100 000 population, respectively. Also, crude and age-adjusted mortality rates reduced from 2.2 to 1.5 and 2.8 to 1.0 per 100 000 population, respectively. Average APC in the incidence and mortality rates showed significant decline both in men (−6.2% and −5.4%, respectively) and women (−5.7% and −4.6%, respectively). Age-specific analysis demonstrated decreases in incidence and mortality rates for every age category, except for the incidence trend in the younger population. Although trends in active TB incidence and mortality rates in Japan have favourably decreased, the rate of decline is far from achieving TB elimination by 2035.

Trend and treatment status of latent tuberculosis infection patients in Japan - Analysis of Japan TB Surveillance data

Objective and method

Management of latent tuberculosis infection (LTBI) is one of the core elements of End TB Strategy. Japan is one of the few countries in which notification of LTBI is mandatory, yet so far, the data has not been analyzed in detail. We thus conducted a cross-sectional study to examine the trend of LTBI, its treatment outcome and factors predicting treatment non-completion in Japan for the period of 2007 and 2014, using the data from the electronic Japan Tuberculosis Surveillance system. Treatment completion was defined as those whose reason for terminating the treatment was recorded as “treatment completed” and whose treatment duration was 180 days or more.

Results

During the study period, a total of 50,268 LTBI patients were notified, of which 49,525, who had started treatment, were analyzed for characteristics. 57.5% were females, and 38.5% were aged 25–44 years. As for the job category, healthcare professionals, that is medical doctors, nurses and other healthcare workers, consisted the largest group (30.4%). Overall, the number of LTBI notification has been on an increase, with a large increase observed among those aged 65 years and above. Of the 49,525 patients, the information regarding reason for termination of treatment was available for 46,128 (93.1%). Of them, 33,156 (71.9%) had completed treatment as according to the study definition. The risk factors for not completing LTBI treatment included being aged 65 years and above (adjusted odds ratio [aOR] 1.27, 95% confidence interval [95%CI] 1.10–1.47), foreign-born (aOR 1.14, 95%CI 1.02–1.28), healthcare professional (aOR 1.44, 95%CI 1.24–1.69), full-time and part-time worker (aOR 1.40, 95%CI, 1.20–1.63) and detected via contact investigation (aOR 1.26, 95%CI 1.12–1.41).

Conclusions

Our study results revealed that the treatment completion rate was 71.9%, falling short of the national target of 85%, and also that the treatment duration was recorded as less than 180 days for approximately 20% of those who were reported as having completed treatment. Further studies may be built on ours to explore the reasons for not completing the treatment across different population groups, and identify those who benefit the most, and who has the greatest impact on ending TB, by receiving LTBI treatment.

Assessment of tuberculosis contact investigation in Shanghai, China: An 8-year cohort study

BACKGROUND

Tuberculosis (TB) contact investigation has been observed as a useful programmatic tool in active case finding. We collected data of contact cases to evaluate the effectiveness of TB contact investigation programme in Shanghai, China.

METHODS

Since 2009, we screened and followed up the close contacts of bacteria-positive TB cases in Songjiang, Shanghai and calculated the incidence of TB in close contacts and confirmed the transmission by genotyping and sequencing.

RESULTS

A total of 4584 close contacts of 1765 contagious TB index cases were followed up for an average of 4 years. About 62 contacts (333/100 000, 95% CI: 256-428) developed TB excluding 6 co-prevalent cases. The contact cases consisted 1.50% (39/2592) of all the bacteria-positive cases in population. Transmission links were confirmed in 60% (9/15) familial contacts and 22% (2/9) in non-familial contacts. Source cases come from more than close contacts and both index and contact cases created other secondary cases in community.

CONCLUSIONS

Familial contacts are more likely to acquire TB from the index, indicating the priority of family members in TB contact investigation in China. However, most non-familial contacts were infected from sources in the community and contact cases attributed little to case finding in the TB-prevalent setting. Thus, active case finding should be strengthened in general population.