They reviewed 18 studies analysing the effectiveness of the six most commonly used C. difficile testing kits available
in the UK.
They found the percentage of ‘false positives’ ranged from 3% to 45%, depending on the test used, and the number of cases missed ranged from 5% to 24%.
As a result, the researchers said that all patients suspected of carrying the infection should have stool samples tested twice to avoid misdiagnosis, rather than the current norm of only one test.
Lead study author Timothy Planche, consultant in medical microbiology at St George’s Healthcare NHS Trust in London, said: ‘A false negative result could mean that infected patients don’t get the right treatment and could pass the infection on to others.
‘Conversely, patients receiving a false positive result may receive inappropriate treatment and be placed in wards along with infected patients, putting them at risk of contracting the infection,’ he said.
But Rose Gallagher, RCN infection control adviser, said management of patients suspected of having the infection should not change. ‘If a patient has diarrhoea and there is a suspicion of infection, they should be isolated and barrier nursing precautions implemented,’ she said.
‘False positive results are not unusual but a patient’s medical treatment is determined by their clinical symptoms. If they are not symptomatic, the patient will not be subjected to clinical treatment,’ she added.
A spokesperson for the Health Protection Agency said it was assessing C. difficile testing kits to see which provided the most reliable results. The results will be available early next year.
The study is published online in The Lancet Infectious Diseases.