Transmission of Mycoba cterium tuberculosis to households of tuberculosis patients: a comprehensive contact tracing study.
BACKGROUND
Tuberculosis (TB) continues to be a major health problem in developing countries. Contact investigation is the most appropriate strategy to interrupt transmission and subsequent development of TB.


METHODS
This cross-sectional study was conducted to assess the impact of contact screening on case-finding by using tuberculin skin test chest radiography. Contacts of smear-positive patients with pulmonary TB (index cases) were diagnosed and registered in our center during 2002 - 2004. Contacts, defined as household members living with index cases for >30 days, were screened by sputum examination, tuberculin skin test, and chest radiography.


RESULTS
Sixty-eight patients with smear-positive pulmonary TB were considered as index cases. A total of 224 close contacts with index cases (an average of 3 contacts for each index case) were detected. Age among contacts ranged from 6 months to 74 years. Eighty-three percent of contacts were Iranians and 17% were Afghans. Abnormal radiographs were seen in 49.6% of contacts. Sixteen point five percent of contacts had a positive tuberculin skin test of >10 mm; 7.6% had a positive sputum smear. The mean +/- SD age of Iranian contacts (29.1 +/- 16.6 years) was significantly (P < 0.001) higher than that of Afghans (18.6 +/- 14.1 years). Cavitary formation, nodular pattern, and infiltration were found to have a strong association with a positive sputum smear for acid fast bacilli (100%, 100%, and 87%, respectively).


CONCLUSIONS
The rate of TB in contacts was higher than other similar studies. Earlier detection and treatment of adults with TB could interrupt transmission and be a step towards eliminating childhood TB. Contact control and source-case investigations should be emphasized for TB control. Novel strategies are needed to maximize the number of contacts who are not only identified and evaluated, but also completely treated.
Khalilzadeh
Soheila
S
National Research Institute of Tuberculosis and Lung Disease, Masih Daneshvari Hospital, Tehran, Iran. skh@nritld.ac.ir
Masjedi
Heidar
H
Hosseini
Mostafa
M
Safavi
Arash
A
Masjedi
Mohammad-Reza
MR
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D016358:Contact Tracing / Q000379:methods*; D003430:Cross-Sectional Studies; D018562:Disease Transmission, Infectious / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007492:Iran / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D013902:Radiography, Thoracic; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000635:transmission*