Background: In the fight against the global tuberculosis epidemic, it is essential to ensure that patients adhere to the treatment prescribed. As the treatment is given for a minimum of 6 months it is common for patients not to take their drugs regularly. Strategies are therefore needed to assess adherence to treatment. One established method is to examine the patient's urine for the presence of drug metabolites. A rapid point-of-care test would overcome some of the drawbacks associated with currently available methods.
Method: A rapid, safe point-of-care test for isoniazid metabolites (IsoScreen, Surescreen Diagnostics Limited, Derby, UK) has been developed and used to help assess adherence to treatment in a busy clinic for tuberculosis patients in South London.
Results: Urine samples were examined from 191 patients receiving isoniazid, usually in combination with rifampicin and other anti-tuberculous drugs. Isoscreen was positive in 93.2% of patients, suggesting that 6.8% might be poorly adhering to treatment. By contrast, examining the same urine samples for evidence of rifampicin ingestion gave positive results in only 43.5%, due to the fact that this test is only positive for a few hours after drug ingestion.
Conclusion: IsoScreen has been shown to provide a rapid and safe point-of-care test, which contributes to the detection of non-adherence in patients with tuberculosis.