TB surveillance in Canada / Response from authors
We recently reported on the immigration medical surveillance program for TB in Ontario.1 While we agree with the assertion of the accompanying editorial2 that TB control must be considered in the global context, we do not agree with the apparent suggestion that TB prevention programs among high-risk immigrants in Canada be discontinued.
Two prospective3,4 and one retrospective5 study in Canada suggest that persons referred for medical surveillance for TB are at increased risk for TB. These studies found that 1.5-2.8% of persons referred for medical surveillance were diagnosed with active TB at their first medical evaluation in Canada. In the Netherlands an immigration screening program detected cases earlier, resulting in fewer hospital admissions, shorter duration of symptoms and therefore probably reduced tuberculosis transmission.6 In the face of the increasing prevalence of TB HIV co-infection and multidrug-resistant TB, tolerance for local transmission needs to be close to zero. Serious attempts to reduce transmission as well as to make a timely diagnosis to optimize the health of the affected individual are required. Clearly operational shortcomings, such as referral of low-risk populations, poor notification and lack of appropriate medical follow-up will seriously compromise the effectiveness of any program.’ The task facing TB controllers in Canada is the repair and maintenance of the referral program.
TB among persons migrating to countries that enjoy a higher level of development will continue to dominate the TB control concerns of the receiving countries. It is the obligation of TB control officers in these countries to protect the interests of their population. It is clear from our study that there are major problems with the medical surveillance program in Ontario. Clearly we are missing opportunities to reduce the future burden of TB in Canada. JULY – AUGUST 2002
We strongly believe that evidence-based redesign of the system will better preserve the health of Canadians than dismantling it.
W. Wobeser M. Naus J. Brunton N. Heywood A. Uppaluri
1. Uppaluri A, Naus M, Heywood N, Brunton J, Kerbel D, Wobeser W. Effectiveness of the Immigration Medical Surveillance Program for Tuberculosis in Ontario. Can J Public Health 2002;93(2):88-91.
2. Cowie RL, Field SK, Enarson DA. Tuberculosis in immigrants to Canada: A global problem which requires a global solution (Editorial). Can ]Public Health 2002;93(2):85-87.
3. Orr PH, Manfreda J, Hershfield ES. Tuberculosis surveillance in immigrants to Manitoba. Can Med Associ 1990;14:453-58.
4. Wang JS, Allen EA, Enarson DA, Grzybowski S. Tuberculosis in recent Asian immigrants to British Columbia, Canada: 1982-1985. Tubercle 1991;72(4):277-83.
5. Wobeser W, Yuan L, Naus M, Corey P, Edelson J, Heywood N, Holness L. Expanding the epidemiologic profile – Risk factors for active tuberculosis among persons immigrating to Ontario. CAJ 2000; 163(7):823-30.
6. Verver S, Bwire R, Borgdorff MW. Screening for pulmonary tuberculosis among immigrants: Estimated effect on severity of disease and duration of infectiousness. Int J Tuberc Lung Dis 2001;5(5):419-25.
7. Schwartzman K, Menzies D. Tuberculosis screening of immigrants to low-prevalence countries. A cost-effectiveness analysis. Am J Respir Crit Care Med 2000;161:780-89.
Response from authors
We are grateful to Dr. Wobeser and her colleagues for giving us the opportunity to clarify the opinion we expressed in the editorial concerning tuberculosis in immigrants.1 We certainly did not intend to imply that the screening of immigrants for tuberculosis was without value. The process does serve to identify and treat those with tuberculosis and those who are at high risk for developing tuberculosis on the basis of their x-ray findings.2 We did, however, wish to emphasize that the immigrant screening process fails to identify nearly 90% of immigrants who subsequently develop tuberculosis.3,4 We therefore proposed that additional interventions were necessary if we are to have an impact on tuberculosis in Canada. We thought that the most effective approach was to assist in global initiatives to deal with this disease.
Robert L. Cowie Stephen K. Field Donald A. Enarson
1. Cowie RL, Field SK, Enarson DA. Tuberculosis in immigrants to Canada: A global problem which requires a global solution (Editorial). Can J Public Health 2002;93(2):85-87.
2. Schwartzman K, Menzies D. Tuberculosis screening of immigrants to low-prevalence countries. A cost-effectiveness analysis. Am J Respir Crit Care Med 2000; 161:780-89.
3. Cowie RL, Sharpe JW. Tuberculosis among immigrants: Interval from arrival in Canada to diagnosis. A 5-year study in southern Alberta. Can Med Assoc J 1998;158:599-602.
4. Uppaluri A, Naus M, Heywood N, Brunton J, Kerbel D, Wobeser W. Effectiveness of the Immigration Medical Surveillance Program for Tuberculosis in Ontario. Can J Public Health 2002;93(2):88-91.
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