Risk of Infection in Active TB Contacts: results from a Contact ...

epidemiologia.it

Risk of Infection in Active TB Contacts: results from a Contact ...

Risk of Infection in Active TBContacts: results from a ContactInvestigation Program in Turin (Italy)Migliore E. 1 , Borraccino A. 2 , Baussano I. 3,4 , Mercadante S. 4 ,Piccioni P. 5 , Carosso A. 5 , Bugiani M. 51 Unit of Cancer Epidemiology and CPO Piemonte2 Department of Public Health - University of Turin3 Imperial College London, 4 UPO/CPO-Piemonte5 CPA ASL-TO2EUROEPI 2010 “Epidemiology and Public Health in an Evolving Europe”Florence, 6 -9 November 2010


Background! Contact Tracing (CT) is the most readily availableintervention to identify recently infected individuals! essential component of the TB prevention, control andelimination strategy for low-incidence country.! The objective of contact investigation are to:! reduce TB morbidity and mortality by earlyidentification and treatment of contacts with active TB;! Prevent transmission by detection of source cases;! contribute to the elimination of TB through preventionof future TB case by detection and preventive therapyof infected contacts at risk of developing TB.(Erkens, 2010; CDC MMWR 2005, )


Objectives! To assess contact investigation outcomes andeffectiveness of contact-tracing;! To investigate the effect of some characteristicsthat could influence the yield of contact tracing.! To evaluate the role of different factors involved inTB infections among contacts of TB cases


Methods! All TB cases (new and relapses) identified by thePiedmont surveillance system and the compulsoryregional notification " years 2002 - 2008.! Index TB cases were divided into three main categoriesof infectiousness, according to CDC policy:! AFB+: both Acid-fast Bacilli sputum smear and culture examin. positive! CULT+: AFB- and positive culture examination! OtD (Other than Defined): both AFB- and CULT-! For each TB case an epidemiological surveillance wasperformed following the Italian guidelines:! Active CT screening for AFB+(Guidelines for Tuberculosis Control, Italian Health Ministry; DL 112/1998)


Methods! All identified Contacts were traced and defined as:! close household contacts (HC)! regular contacts (RC) and! occasional contacts (OC)! contacts reached were evaluated for a previous BCGvaccination (with scar inspection) and screened for aTB infection.! Tuberculin Skin Test (TST) was performed using purifiedprotein derivative (PPD) 5 UI according to Mantouxmethod (defining the positive reaction for a diameter ! 5 mm).


Results - Characteristics of TB cases! 1099 pulmonary TB cases (1 st Jan 2002 -31 st Dec 2008)! 62.3% males! 51.1% foreigner! 46.7% AFB+ (N=513); 13.4% CULT+; 36.0% OtD! 833 (75.8%) TB cases were screened for contacts! 58.9% males! 47.7% foreigners! 14.8% communities! 53.7% AFB+ (N=447); 14.4% CULT+; 26.8% OtD! For 266 people the information on contacts is unknown! The median number of contact per case was 3.


Results - Characteristics of contacts! Overall 4759 contacts were identified! 53.4% females;! 28.6% foreigners;! 73.8% household contacts; 15.8% regular contacts;Median age = 34 (IQR 24-47)


Results: contact tracing yieldN= 4759OtDOtDCULT+CULT+(93.3%) § (82.8%) § (45.0%)*OtDCULT+AFB+AFB+AFB+OtDCULT+§- on contacts identified* - on contacts evaluatedAFB+N=28 (0.7%)*TB RateAmongcontactsOR CI95%Contact age 0.98 0.97;0.99Contact nationality 0.52 0.35;0.77OR CI95%Household 2.33 1.13; 4.81Regular contact 2.75 1.12; 6.72


Results: factors in TB infection! Role of different factors involved in TB infections amongcontacts of TB cases, by age of contact (OR and CI 95%)1Age of contact ! 35 yrs2.60.61Age of contact > 35yrs4.70.51.70.92.11.14.74.8OROR


Discussion! Contact tracing yield! The result is satisfying! 83.9 % (contact evaluated on identified)! International GL suggest to exceed 80%! TB Rate among contacts is about 60 timeshigher than the expected in the Italianpopulation! 700*10 -5 vs 10-11*10 -5(ISS, Rome 2008)


Discussion! CT is to be considered a good means for collectingTB cases, especially for an AFB+ index case! Factors involved in the TB infection among contactsare different, depending on age:! 35 years of age! Population risk factor (cohort effect and contact age)prevail on the index case effect


Conclusion! the study results showed a better cost/efficacyperformance when the contact investigation isconducted among:! household contacts and regular contacts inchildren adolescents and young adults withan AFB+ index case, as suggested by WHOand CDC guidelines.

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