February 9, 2010
The authors designed a long-term cohort study in Karonga district, rural Malawi, to estimate rates of recurrent tuberculosis due to re-infection and relapse, by HIV status, in a general population.
All TB patients with culture-proven disease in the district were followed up after treatment, with HIV testing offered and all M. tuberculosis isolates fingerprinted using IS6110 RFLP. The researchers compared fingerprints from initial and recurrent disease episodes to distinguish relapse and re-infection: a second episode was considered a relapse if the fingerprint was identical or differed by only one to four bands and was the first occurrence of that pattern in the population. Survival analysis and Poisson regression were used to estimate rates of and risk factors for recurrence, re-infection disease and relapse.
During 1995 to 2003, 584 culture-positive TB episodes were diagnosed and treatment was completed in patients with known HIV status; 53 culture-positive recurrences occurred by May 2005. Paired fingerprints were available for 39 of these. Re-infections accounted for 1/16 recurrences in HIV-negative and 12/23 in HIV-positive patients. Relapse rates were similar in HIV-positive and HIV-negative individuals. Using multiple imputation to allow for missing fingerprint information, the rate of re-infection disease in HIV-positive patients was 2.2/100 person-years and 0.4/100 person-years in HIV-negative individuals.
"HIV increases the rate of recurrent tuberculosis in this setting by increasing the rate of re-infection disease, not relapse," concluded the authors.
01.28.10; Vol. 24; No. 3: P. 417-426; Amelia C. Crampin, J. Nimrod Mwaungulu, Frank D. Mwaungulu, D. Totah Mwafulirwa, Kondwani Munthali, Sian Floyd, Paul E.M. Fine, Judith R. Glynn