Our study examined trends in extrapulmonary tuberculosis in the UK and investigated the factors associated with recent changes highlighting this to clinicians.1 Jolobe summarises reports from the USA and anecdotal media coverage of patients in whom the diagnosis of pulmonary tuberculosis was delayed due to the perception of low risk in native-born patients who subsequently presented with advanced pulmonary disease. We have previously reported delayed diagnosis in these groups in the UK.2 As pulmonary tuberculosis is the infectious form of the disease with significant consequences of delayed diagnosis on the control effort and possible adverse clinical outcomes, we agree that the index of suspicion in patients with signs and symptoms suggestive of pulmonary tuberculosis should remain high.

This, however, raises an important clinical conundrum about uncommon illnesses. Among UK-born white adults aged 15–45 years, only 299 of 375 cases were reported with pulmonary tuberculosis. The number of cases in this subgroup of the population has remained relatively stable. A significant proportion of these will be individuals with other risk factors for tuberculosis such as homelessness and drug use or identified as contacts of a case of infectious tuberculosis. If every person with, for example, a cough lasting 3 weeks is investigated for tuberculosis, this will result in significant unnecessary investigation, especially in primary care. With <9000 cases in a population of 60 million, the majority of whom are resident in urban areas,3 the average general practitioner in a rural area in the UK may not see a single case of tuberculosis in several years.

Nevertheless, given the consequence of pulmonary tuberculosis to the individual and society, it is appropriate for clinicians and general practitioners to ensure that tuberculosis is among the differential diagnoses in patients with relevant symptoms and signs and to investigate for tuberculosis fairly promptly. Every attempt should be made to obtain a microbiological diagnosis. As Jolobe points out, it is also true that patients with smear-negative culture-positive tuberculosis can transmit infection, although less so than those who have a positive smear from direct sputum examination.4 Exclusive extrapulmonary tuberculosis is, however, not infectious and the suggestion to the contrary is erroneous.

In view of the current rise in the incidence of tuberculosis, without high case detection and the adequate treatment of cases, tuberculosis may not remain an uncommon illness in the UK. Vigilance for both pulmonary and extrapulmonary tuberculosis is required.