© 2006 American Thoracic Society
From the Authors:We thank Drs. von Reyn and Horsburgh for their interest in our study on the rate of tuberculosis (TB) attributable to reinfection (1). Their comment that part of the high reinfection rate is due to HIV may be true, but we do not agree that HIV explains all of the effect for two reasons. First, their observation that the proportion of patients with TB coinfected with HIV of 11% represents the lowest rate in sub-Saharan Africa is probably correct. Official voluntary counseling and testing (VCT) figures from the epidemiologic site for 2004 show that 85% of patients with TB were counseled for HIV, 92% accepted testing, and 10% of those tested were HIV positive (V. Azevedo, Department of Health, Cape Town Municipality, South Africa, personal communication). The study took place in a community where the HIV prevalence rate is considerably lower than in other communities in South Africa, and cases enrolled had their first episode of TB between 1993 and 1998, a time when HIV prevalence was even lower than in 2004. We knew the HIV status at the first disease episode of 14 of the 27 patients with a reinfection: 13 of 14 were HIV-negative. We knew the HIV status for 8 of these 13 at the second episode: all were HIV negative. Second, the reinfection disease rate of 0.75/1,000 patient-years (p-yr) that von Reyn and Horsburgh calculate for HIV-negative patients with TB is still 1.5 times the age-adjusted incidence rate that we found for HIV-positive and HIV-negative new patients with TB together (0.51/1,000 p-yr). Von Reyn and Horsburgh speculate that culture-negative cases have a stronger adaptive immune response with reduced susceptibility to disease after reinfection. This may be true, but does not undermine our findings, which are relevant for culture-positive disease. Moreover, the study quoted was one undertaken in a context where the majority of patients were HIV-positive and may not be relevant to a population of mainly HIV-negative patients such as the one that we studied. We agree with the final point that there are currently no methods to measure reinfection in individuals with latent infection only. This means that any protective effect of latent infection for disease after reinfection is at present uncertain.
Stellenbosch University, Cape Town, South Africa and KNCV Tuberculosis Foundation The Hague, The Netherlands
Stellenbosch University, Cape Town, South Africa
KNCV Tuberculosis Foundation, The Hague, The Netherlands and Academic Medical Center, Amsterdam, The Netherlands
International Union Against Tuberculosis and Lung Disease (IUATLD) Paris, France
McGill University Health Center, Montreal, Quebec, Canada FOOTNOTES Conflict of Interest Statement: S.V. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. R.M.W. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. N.B. received £111,150 in 2000, £150,000/year for 2001–2003, and £85,000 in 2004 from the GlaxoSmithKline Action TB Program as research grants for developing and maintaining an epidemiologic field site and for doing a study aimed at identifying surrogate markers for response to treatment in patients with TB. She received £500 in 2003 for speaking at a conference where one session was sponsored by GlaxoSmithKline (GSK). G.D.v.d.S. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. M.W.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. D.A.E. participated in an advisory workshop for GSK concerning Drugs for Diseases of the Developing World, held in England on December 12, 2003. He received no remuneration for this participation. He has been a member of the advisory board of the Aventis Nelson Mandela Project in South Africa since September 2003. He has received no remuneration for this activity. M.A.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. He does have a patent (U.S. 6,291,190), but this is related to BCG vaccines and is unrelated to this manuscript. P.D.v.H. has received a research grant of 1.5 million Rand/year from GSK for searching for surrogate markers for antibiotic response during TB therapy. REFERENCES
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