The previous study was from Canada where late presentation of tuberculosis may have been rare and thus the proportion of cases with a heavy bacillary load that was demonstrable by microssopy contributed only 60 per cent of all culture-confirmed tuberculosis. In settings where accessibility to diagnostic services (distance, costs, etc) is more difficult, it is conceivable that the bacillary load of patients at diagnosis is larger and thus the relative additional contribution of culture-only positive tuberculosis is smaller and /or the culture technique is less sensitive than in the former setting
This appears to have been the case in this outpatient clinic in Harare, where culture contributed a very small proportion of cases in the diagnosis of pulmonary tuberculosis and interestingly rather independent of whether the patient was HIV infected or not.
