Tuberculosis management time: an alternative parameter for measuring the tuberculosis infectious pool.

OBJECTIVE: To demonstrate the application of TB management time as an alternative parameter to estimate the size of the tuberculosis infectious pool in West Gojjam Zone of Amhara Region, Ethiopia. METHODS: In this study, we used the TB management time, i.e. the number of days from start of cough until start of treatment, to determine the infectious period. Patients with sputum smear-positive and smear-negative pulmonary TB, retreatment and an estimated number of undetected cases were included. The infectious pool was then estimated as the annual number of infectious person days in a defined population. RESULTS: The TB management time of presently undiagnosed TB cases and sputum smear-positive patients contributed significantly to the infectious pool with 151,840 and 128,750 infectious person days per year, respectively. The total infectious pool including sputum smear-negative TB cases and retreatment patients in the study area was estimated at 325,410 person days or 15,447 person days per 100,000 population during the study year. CONCLUSION: Recording TB management time may be used to estimate the infectious pool of TB and to monitor programme performance in the community.

Allergic sensitisation in tuberculosis patients at the time of diagnosis and following chemotherapy.

BACKGROUND: It is still a matter of debate whether there is an association between infection with Mycobacterium tuberculosis (M. tuberculosis) and allergy. Previously, we have shown higher levels of specific IgE to different inhalant allergens and total IgE in tuberculosis (TB) patients compared to controls. The objectives of this study were to evaluate a possible change in allergic sensitisation after successful TB treatment and to confirm the finding of our previous study of enhanced allergic sensitisation in TB patients compared to controls in a more controlled setting. Additionally, we wanted to determine the cytokine profile in the same groups and finally to evaluate the association between the presence of Bacillus Calmette-Guérin vaccination (BCG) scar and allergic sensitisation among the controls. METHODS: Sera were analysed for specific IgE to inhalant allergens (Phadiatop) and total IgE by the use of ImmunoCAP 1000 (Pharmacia Diagnostics). Thirteen different cytokines were also analysed in the sera by multiplex bead immunoassay (Luminex 100, Luminex Corporation), and clinical symptoms of allergy and BCG scar were reported in a questionnaire. RESULTS: A reduction in levels of specific and total IgE were observed after successful TB treatment. TB patients also had higher levels of specific and total IgE compared to healthy controls. Both interleukin (IL)-6 and interferon (IFN)gamma were higher in TB patients compared to healthy controls. The levels of IL-6 were reduced after successful TB treatment. The presence of a BCG scar was associated with a reduced risk of developing allergic sensitisation. CONCLUSION: We observed a reduced level of allergic sensitisation after successful TB treatment. TB patients seem to be more allergically sensitised than healthy controls, confirming our previous finding. Furthermore, we observed an inverse association between allergic sensitisation and visible BCG scar, which adds additional support to the hygiene hypothesis.

Can treatment delay be utilized as a key variable for monitoring the pool of infectious tuberculosis in a population?

BACKGROUND: A major goal of tuberculosis control programs is to stop community transmission of Mycobacterium tuberculosis. However, this can not be rapidly accomplished because, in endemic areas, most of the population is already infected, serving as a reservoir that continuously contributes to the pool of infectious cases. Tuberculin surveys are the main tools used to monitor the infectious pool, but there are serious methodological constraints, and they require resources and expertise that are often unavailable. There is an urgent need for alternative means to monitor the epidemic at the local level. METHODOLOGY: We investigated whether a systematic registration of treatment delay in the tuberculosis program records of the Amhara Region of Ethiopia could be utilized to estimate the infectious pool of tuberculosis. RESULTS: The study showed that the total number of infectious days and hence an estimate of the infectious pool could be calculated by recording the treatment delay for new TB cases, retreatment cases and failures, and by estimating the number of undiagnosed cases. Of these categories, treatment delay among new smear-positive tuberculosis cases contributes the greatest number of infectious days. CONCLUSIONS: A local tuberculosis program can use a systematic recording of treatment delay as a quantifiable variable to monitor the infectious pool, and can also serve as a key indicator of program performance.