Time-to-detection in culture of Mycobacterium tuberculosis: performance for assessing index cases contact-positivity

OBJECTIVES

Time-to-detection (TTD) in culture on liquid media is inversely correlated to bacillary load and should be a contributing factor for assessing tuberculosis transmission. We wanted to assess if TTD was a better alternative than smear status to estimate transmission risk.

METHODS

From October 2015 to June 2022, we retrospectively studied a cohort of index cases (IC) with pulmonary tuberculosis (tuberculosis disease [TD]) from which samples were culture-positive before treatment. We studied the correlation between TTD and contact-positivity (CP) of IC contacts: CP was defined as CP = 1 (CP group) in case of TD or latent tuberculosis infection (LTI) in at least one screened contact of an IC, and CP = 0 otherwise (contact-negativity [CN] group). Univariate and multivariable analyses (logistic regression) were done.

RESULTS

Of the 185 IC, 122 were included, generating 846 contact cases of which 705 were assessed. A transmission event (LTI or TD) was identified in 193 contact cases (transmission rate: 27%). At day 9, 66% and 35% of the IC had their sample positive in culture for CP and CN groups, respectively. Age and TTD ≤9 days were independent criteria of CP (odds ratio 0.97, confidence interval [0.95-0.98], P = 0.002 and odds ratio 3.52, confidence interval [1.59-7.83], P = 0.001, respectively).

CONCLUSION

TTD was a more discriminating parameter than smear status to evaluate the transmission risk of an IC with pulmonary tuberculosis. Therefore, TTD should be considered in the contact-screening strategy around an IC.

Risk of latent tuberculosis infection among healthcare workers in Italy: a retrospective study with Quantiferon Test

OBJECTIVE

The latent tuberculosis infection (LTBI) is a state of persistent immune response to stimulation by Mycobacterium Tuberculosis antigens without clinical manifestation: the healthcare workers (HCWs) have a higher exposure risk so prevention is an important challenge for occupational medicine. The aim of our study is to evaluate the prevalence of LTBI among HCWs of the Foundation Policlinic "Tor Vergata".

METHODS

This is a retrospective study conducted by analyzing the clinical records of 825 HCWs of the PTV, from January 1st to December 31th 2016. To evaluate the TB infection we used the Quantiferon TB Gold interferon-gamma release assay.

RESULTS

Our study underlines the low prevalence of LTBI in the Italian healthcare workers.

CONCLUSION

Although the LTBI status is not contagious, the diagnosis and the safety strategies require specific clinical and preventive considerations.

Community health volunteers' contribution to tuberculosis patients notified to National Tuberculosis program through contact investigation in Kenya

BACKGROUND

Contact investigation is important in finding contacts of people who have Tuberculosis (TB) disease so that they can be given treatment and stop further transmission. The main objective of this study was to assess the contribution of community health volunteers (CHVs) to the number of TB patients notified to the National program in Kenya through household contact screening and referral of persons with TB signs and symptoms to the facilities for further investigation.

METHODS

This was a retrospective desk review of project reports submitted to Amref Health Africa in Kenya by the sub-recipients implementing activities in the 33 counties with Case Notification Rate (CNR) of less 175/100,000 and Treatment Success Rate (TRS) of less than 88% as per the National strategic plan 2015-2018. Data for this study covered a period between January and December 2016. Data on the notified TB patients was obtained from the National Tuberculosis Information Basic Unit (TIBU). The study population included all the TB index cases whose households were visited by CHVs for contact screening. Data was recorded into excel spreadsheets where the descriptive analysis was done, proportions calculated and summarized in a table.

RESULTS

Community health volunteers visited a total of 26,307 TB patients (index cases) in their households for contact screening. A total of 44,617 household members were screened for TB with 43,012 (96.40%) from households of bacteriologically confirmed TB patients and 1606 (3.60%) from households of children under 5 years. The proportion of the persons referred to the number screened was 19.6% for those over 5 years and 21.9% from under 5 years with almost the same percentages for males and females at 19.2% and 19.7% respectively. The percentage of (TB) cases identified through tracing of contacts in these counties improved to 10% (5456) of the 54,913 cases notified to the National TB Program.

CONCLUSIONS

This study showed that in the 33 counties of Global Fund TB project implementation, the percentage of TB cases identified through tracing of contacts improved from 6 to 10% while the percentage of notified TB cases; all forms contributed through community referrals improved from 4 to 8%. Community health volunteers can play an effective role in household contact screening and referrals for the identification of TB.

A review of the current public health practice for contact tracing in relation to laryngeal TB in England 2012-2016

OBJECTIVES

Contact tracing following identification of tuberculosis (TB) is well established. However, evaluation of this activity, particularly for laryngeal TB, is limited. We compare contact tracing and outcomes in response to laryngeal TB with sputum-smear-positive pulmonary TB (ss + pTB) and consider the public health response in light of our findings.

STUDY DESIGN

This study is a comparative secondary analysis of retrospective data, extracted from TB surveillance systems, to determine differences in contact tracing process and outcomes between two groups.

METHODS

Cases of laryngeal TB (without ss + pTB) notified in England between 2012 and 2016 were selected and matched to ss + pTB controls. Number of contacts identified and screened, along with screening outcomes were gathered from local databases.

RESULTS

There were 44 laryngeal TB cases who met inclusion criteria. The median number of contacts identified per case was 3 and 4 for controls (P = 0.04). Median number of contacts screened was 3 for cases and 4 for controls. The percentage of contacts with TB was 9.7 for cases and 20.3 for controls (P < 0.01).

CONCLUSION

We observed a small difference, between case and control groups, in number of contacts identified but not number screened, indicative of a broadly similar approach to contact tracing. Conversely, the difference in screening outcomes between the groups was significant. These findings highlight a potential need to further understand infectivity of laryngeal TB; and consider possible implications for public health practice.

Risk of infection and disease progression in children exposed to tuberculosis at home, Colombia

Aim:

To assess the risk of tuberculosis (infection and disease) in children less than 15 years’ old who are household contacts of pulmonary tuberculosis patients in three Colombian cities (Medellín, Cali, and Popayán).

Methods:

A cohort of 1,040 children household contacts of 380 adults with smear-positive pulmonary tuberculosis was followed up for 24 months. Study period 2005-2009.

Results:

Tuberculin skin test was positive (≥10 mm) in 43.7% (95% CI: 39.2-48.2). Tuberculin skin test positivity was associated with age 10-14 years (Prevalence Ratio -PR= 1.43, 95% CI: 1.1-1.9), having a BCG vaccine scar (PR= 1.52, 95% CI: 1.1-2.1), underweight, closer proximity to the index case and exposure time >3 months. The annual risk of infection (tuberculin skin test induration increase of 6 mm or more per year) was 17% (95% CI: 11.8-22.2) and was associated with a bacillary load of the adult index case (Relative Risk -RR= 2.12, 95% CI: 1.0-4.3). The incidence rate of active tuberculosis was 12.4 cases per 1,000 persons-year. Children <5 years without BCG vaccine scar had a greater risk of developing active disease (Hazard Ratio -HR= 6.00, 95% CI: 1.3-28.3) than those with scar (HR= 1.33, 95% CI: 0.5-3.4). The risk of developing active tuberculosis augmented along with the increase from initial tuberculin skin test (tuberculin skin test 5-9 mm HR= 8.55, 95% CI: 2.5-29.2; tuberculin skin test ≥10 mm HR= 8.16, 95% CI: 2.0-32.9).

Conclusions:

There is a need for prompt interruption of adult-to-children tuberculosis transmission within households. Conducting proper contact investigation and offering chemoprophylaxis to infected children could reduce tuberculosis transmission.

House-hold contact tuberculosis screening adherence and associated factors among tuberculosis patients attending at health facilities in Gondar town, northwest, Ethiopia

BACKGROUND

Contacting patients with tuberculosis have a substantial risk of developing the disease. Household contact screening has recently been recommended as a strategy to enhance case detection in high-burden countries. But there is no enough information in Gondar town regarding household contact screening practice among TB patients.

METHODS

An institution-based cross-sectional study was conducted from March 1 to 30, 2019 on 404 tuberculosis patients attending at health facilities in Gondar Town. Epi-Info version 7 for data entry and SPSS version 20 for data analysis were used. Descriptive statistics were carried out to illustrate the means, standard deviations, and frequencies. Bivariable and multivariable logistic regression analyses were used to identify significantly associated variables with the dependent variable.

RESULTS

From 412 study populations, 404 were completed the study with 98.06% response rate. The overall household contact TB screening adherence was 47.5% (95% CI: 43.1, 52.5). In the multivariable analysis, having certificate and above educational level (AOR = 2.83, 95% CI:1.40,5.67), having sufficient knowledge about TB (AOR = 8.26, 95% CI:4.34,15.71), being satisfied with health care service (AOR = 3.26, 95% CI:1.58,6.76), health education given by health care workers (AOR = 2.60, 95% CI:1.54,4.40),and having HIV/AIDS co-infection (AOR = 3.54, 95% CI:1.70,7.39), were factors associated with household contact TB screening adherence.

CONCLUSION

Compared to other previous studies, the current finding was high but it was low as compared with WHO and Ethiopian Ministry of Health recommendations (all persons having TB contact should be screened). Educational status, knowledge on TB, satisfaction with delivered health care service, health education given by HCWs about TB and HIV/AIDS co-infection were factors associated with household contact TB screening practice. Thus, strengthening household TB contact screening and educational programs regarding the risk of getting TB infection from household contacts is crucial.

Contact screening and risk factors for TB among the household contact of children with active TB: a way to find source case and new TB cases

Background

Source case investigation, for children with tuberculosis (TB), is conducted to establish the source of infection and to minimize the extent of on-going transmission from infectious persons in the community. The aim of the study was to evaluate the secondary TB cases and to investigate the risk factors in developing TB among the household contacts (HHC) of children with active TB.

Methods

A prospective cross-sectional study was conducted where 443 caregivers, of 508 children with active TB receiving treatment, were interviewed using a structured questionnaire. Logistic regression analysis was used to examine the risk factors for TB.

Results

A total of 2397 family members at the median of 5 persons were recorded. Of these, 223 (9.3%) were screened on symptoms basis and 35 (15.7%) of these contacts were diagnosed with TB. Multivariate analysis revealed HHC with TB (OR = 15.288, 95% CI: 5.378–43.457), HHC with smoking (OR = 7.094, 95% CI: 2.128–23.648), and contact of > 18 h with TB individual (OR = 4.681, 95% CI: 1.198–18.294) as statistically significant risk factors of TB among the HHC.

Conclusion

With the current system of contact screening for TB, only 9.3% of all HHC were screened. The low rates of contacts screened are possibly a repercussion of the passive nature of the program, which mainly depend on distinctive clinical symptoms being experienced by the contacts. Strategies are required to certify adherence with contact screening among children with active TB and to critically consider the factors responsible for TB transmission.

Prevalence and Risk Factors for Latent Tuberculosis Infection among Healthcare Workers in a Low Incidence Country

Background:

Tuberculosis prevention is a major goal in the hospital setting. Because of the possible progression or reactivation of latent disease, the screening of healthcare workers is an important issue in the TB control program. The aim of the study was to assess the prevalence of LTBI (latent tuberculosis infection) and to evaluate the main risk factors related to this condition in a teaching hospital in Italy.

Methods:

We reviewed the data of a tuberculosis screening conducted on 3622 healthcare professionals in a teaching hospital in Rome. All subjects were evaluated by QuantiFERON test which if positive, was followed by appropriate clinical and diagnostic procedures.

Results:

Latent Tuberculosis Infection LTBI condition was detected in 2.1% of the cases, most commonly in men. Male gender, higher age class, country of birth and nurse job were statistically related with the positivity to QuantiFERON test.

Conclusion:

LTBI was relatively uncommon in our population, however, given the potential risk of reactivation and progression to overt disease, the screening of healthcare workers and students is recommended in the hospital of low-incidence countries.

Trends and patterns in leprosy in nine states of the Republic of the Sudan 7 years after the introduction of routine contact screening

Background

This paper analyzes the trends of key indicators reflecting the epidemiological situation of leprosy in nine different states of the Republic of the Sudan after the introduction of a systematic contact screening in 2010.

Methods

The routinely assessed data from the leprosy control program from 2010 to 2016 were analyzed.

Results

Despite, intense contact screening, the overall number of new cases detected showed a decreasing trend. The female:male ratio among new cases was constantly low. The overall average number of contacts needed to screen in order to detect a new case among contacts was 64. However, this number varied significantly in the nine states under investigation, with the best yield being observed in the state with the lowest case detection rate.

Conclusions

The total number of new cases of leprosy in nine states of the Republic of the Sudan has shown declining tendencies since 2010. Our data are not suggestive of a significant impact of contact screening on the trends of leprosy key indicators. Overall, contact screening proved to be efficient in most states, including those that exhibited very low annual new case detection rates (ANCDRs). Sensitization of personnel undergoing training and measures improving access of females to leprosy services are urgently needed.

Active case finding of rifampicin sensitive and resistant TB among household contacts of drug resistant TB patients in Andhra Pradesh and Telangana states of India - A systematic screening intervention

BACKGROUND

India has the world's highest estimated burden of multi-drug-resistant tuberculosis (MDR-TB). While prevalence of MDR-TB is known to be 2-3% among new TB patients and 12-17% in previously treated patients, programmatic information on the extent of transmission of TB and MDR-TB among household contacts of known MDR-TB patients is scarce. Systematic screening of household contacts of all MDR-TB patients on treatment was implemented as an intervention in the states of Andhra Pradesh and Telangana states of India. We undertook this prospective interventional study to measure the extent of TB symptoms developed among the household contacts of the known MDR-TB patients treated under Revised National TB Control Programme (RNTCP). The extent of rifampicin sensitive or resistance TB, bacteriologically confirmed using Xpert MTB-RIF, was examined among the symptomatic household contacts.

METHODS

All MDR-TB patients registered and on treatment under RNTCP between July 2011 and Sep 2013 in Andhra Pradesh and Telangana States were selected for the study. They were contacted through home visit by the trained RNTCP teams during 11th Dec 2013 and 7th Jan 2014. All household contacts of MDR-TB patients were screened once for TB symptoms such as cough, fever, weight loss, night sweats, and haemoptysis and extra pulmonary site specific symptoms if any. If found symptomatic, two sputum specimen were collected (spot-morning) from each of the contact and transported for testing on Xpert MTB-RIF for detection of pulmonary TB with or without RR-TB.

RESULTS

A total of 1750 MDR-TB patients were registered between July 2011 and Sep 2013. Of these, 1602 (91.5%) MDR-TB patients were included in the study. A total of 4858 household contacts of these 1602 patients were identified with an average of 3 contacts per MDR-TB patient. Of these, after excluding 87 (1.8%) contacts with past history of diagnosis and/or treatment for TB, 4771 (98.2%) contacts were screened for current signs and symptoms suggestive of TB. Their mean age was 28.5 years and 2151 (45%) were females. Of the 4771 contacts screened, 793 (16.6%) had at least one of the symptoms suggestive of TB of whom 781 (98.5%) had two sputum specimen transported and tested on Xpert MTB-Rif. Specimen could not be collected during the study period in 12 symptomatic patients including 4 with symptoms of extra pulmonary TB. Among 781 symptomatic contacts examined, 34 (4.4%) were bacteriologically confirmed with TB and 15 (44%) also had Rif resistance (RR).

CONCLUSIONS

High extent of TB, particularly RR-TB was observed among household contacts of known MDR-TB patients with symptom screening and early diagnosis using Xpert-MTB-Rif. Regular systematic active screening for TB and MDR-TB among this highly vulnerable group using Xpert-MTB-Rif is useful in India for early diagnosis among close contacts of known MDR-TB patients.

TST positivity in household contacts of tuberculosis patients: a case-contact study in Malawi

BACKGROUND

Screening household contacts of active tuberculosis (TB) patients is recommended for TB control. Due to resource constraints this rarely occurs in lower income countries. Demographic and clinical features of index cases may influence the likelihood of onwards TB transmission. It has also been proposed that accumulation of intracellular lipid bodies within M. tuberculosis cells may also enhance bacterial transmissibility. This study explored whether clinical and bacteriological observations recorded at baseline in TB cases in Malawi could help identify those with the highest risk of onwards transmission, to prioritise contact tracing.

METHODS

In this case-contact study, data on clinical presentation, sputum bacterial load and the percentage of lipid body positive acid-fast bacilli (%LB + AFB) on sputum smears were recorded in adults with sputum smear and culture positive pulmonary TB before initiation of therapy. The Tuberculin Skin Test (TST) was used to detect infection with M. tuberculosis amongst household contacts under the age of 15 years. TST positivity of the child contacts was related to characteristics of the index case.

RESULTS

Thirty four index cases brought 56 contacts (median: 1, range: 1-4 contacts each). 37 (66%) of contacts had a positive TST. Cavities or a high percentage of lung affected on index patient CXRs were associated with TST positivity. Multivariate analysis of non-radiological factors showed that male sex, HIV-negative status and raised peripheral blood white blood count (WBC) in index patients were also independent risk factors of TST positivity. Lower %LB + AFB counts were associated with TST positivity on univariate analysis only.

CONCLUSION

TST positivity is common amongst household contacts of sputum smear positive adult TB patients in Malawi. Contact tracing in this high risk population could be guided by prioritising index cases with CXR cavities and extensive radiological disease or, in the absence of CXRs, those who are HIV-negative with a raised WBC.