Oral steroids raise risk of TB five-fold

Patients on oral glucocorticoids are five times as likely as other patients to develop TB, according to an analysis of UK data.

GPs should update their procedure for prescribing the drugs to include more detailed assessment of patients' TB risks, the researchers suggested.

They used the General Practice Research Database to perform a case-control study. This included 497 patients receiving six months of treatment for a first-time diagnosis of TB each matched with up to four controls.

Patients currently taking glucocorticoids were found to have a five-fold increased risk of developing TB compared to those not exposed to the drugs, once BMI, smoking and pulmonary disease were taken into account.

Patients who had not taken the drugs in the past six months were still up to four times more likely to develop TB, even if they had only had one prescription.

All levels of glucocorticoid use were associated with extra TB risk.

The American Thoracic Society advises a maximum daily dosage of 15mg of prednisone or equivalent as part of its TB risk control guidelines. But patients receiving a dose under this threshold were still nearly three times as likely to develop TB as those not on the drugs.

Glucocorticoids have a variety of depressive effects on the cellular immune response. As well as reducing numbers of circulating monocytes and inhibiting their movement, they hamper T-cell activation.

Lead researcher Dr Susan Jick, of Boston University School of Medicine, said that, although it had been suspected that glucocorticoids could increase TB risk, this was the first firm evidence.

'There were only anecdotal reports of an effect. We used what is probably the best database for drug safety in the world to find out if it did exist,' she said.

'These drugs are used for a wide range of conditions such as asthma, colitis and lupus.

'It seems sensible that if you are going to be putting people on these drugs then you should be aware of their other risk factors, and the levels of TB incidence in their neighbourhood.'

Diabetes and a BMI below 20 were also identified as risk factors for TB. Diabetes raised TB risk almost four-fold and a low BMI was associated with a three-fold increase. Smoking and a history of pulmonary disease also raised the risk.

Arthritis and Rheumatism, 2006; 55:19-26

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