London TB study shows women and white males diagnosed later than others

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Caucasian men and women of all ethnicities in London are being diagnosed later than other Londoners for tuberculosis (TB) of the lung, leading to the risk of poorer clinical outcome and further spread of the disease, according a study in the April 26th issue of the British Medical Journal (BMJ).

Researchers from the Infectious Disease Epidemiology Unit at the London School of Hygiene and Tropical Medicine analysed data from 853 patients in London with a positive pulmonary sputum test for mycobacterium tuberculosis (M.Tb) between 1998 and 2000, and found that the median delay between the onset of symptoms and treatment for TB was 49 days (range 14-103).

In multivariate analysis, sex and ethnic group were significantly associated with delay in treatment. Although Caucasian (white) patients accounted for more than 30% of total TB cases, 62% had their diagnosis delayed longer than the median 49 days. Those who were identified as being black, from the Indian continent, or of other non-white ethnicity were more likely to be diagnosed faster than caucasians (adjusted odds ratio 0.52, 0.64, 0.73 and 1, respectively; p = 0.03)

Glossary

multivariate analysis

An extension of multivariable analysis that is used to model two or more outcomes at the same time.

odds ratio (OR)

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 

pulmonary

Affecting the lungs.

 

immune system

The body's mechanisms for fighting infections and eradicating dysfunctional cells.

epidemiology

The study of the causes of a disease, its distribution within a population, and measures for control and prevention. Epidemiology focuses on groups rather than individuals.

Women accounted for 40% of total TB cases identified, and yet 57% received a delayed diagnosis compared with the median. Compared with men, women were 1.46 times more likely to have their diagnosis delayed (p

The authors suggest that the differences may happen due to health care worker bias. However, they admit that they did not take into account the relative contribution of those infected with TB in presenting late.

The authors also note that they did not look at the differences between those patients with both HIV and TB and those with TB only. People with HIV are at greater risk of developing primary TB when first exposed to the bacteria, and the weakening of the immune system makes them much more likely to develop reactivation TB. Active TB can cause a large increase in HIV viral load, which usually decreases again once the TB is properly treated.

According to figures from the UK’s Communicable Disease Surveillance Centre, there were 40.3 TB cases per 100,000 in London, compared with the national average of 12.9 TB cases per 100,000. “TB is rising at an alarming rate in London, and if it is not diagnosed quickly, patients can develop more severe illness or transmit the disease to other people,” said Dr. Rodger.

The authors conclude that recent TB awareness campaigns that have targeted ethnic minority groups be expanded to include the general population.

Further information on this website

Tuberculosis - factsheet

Tuberculosis - overview

References

Rodger A et al. Delay in the diagnosis of pulmonary tuberculosis, London, 1998-2000: analysis of surveillance data. BMJ 326: 909-910, 2003.