C diff cases 'missed by testing'

12 April 2012

Tests for the Clostridium difficile infection are missing up to 20% of cases and falsely diagnosing thousands of others, researchers have said.

A study by St George's, University of London, and St George's Healthcare NHS Trust found that the six most commonly used tests for the hospital bug gave inaccurate results in a number of cases.

As a result of the findings, researchers have recommended that patients are subjected to two-stage testing in order to avoid misdiagnosis.

The study, which will be published on The Lancet's Infectious Diseases website and in the December issue of the medical journal, reviewed 18 studies of the effectiveness of the current tests.

Scientists found that as many as 20% of positive results for C diff may be false - meaning that around 11,000 patients may have been falsely diagnosed with the infection in the last year. Tests were also found to be missing up to 20% of real C diff cases, leading to infected patients not receiving the right treatment and potentially passing the infection on to others.

C diff is a hospital-acquired infection which can lead to diarrhoea and severe inflammation of the bowel and can be fatal. Patients on antibiotics and the elderly are most at risk, with over 80% of those infected with C diff being over 65.

Currently, patients across the NHS are diagnosed with a single test, based on the level of a toxin produced by the bacteria in stool samples, but St George's Hospital has been piloting a two-stage testing process over the past six months.

Researchers said the first test in this two-stage process would be a quick test to weed out negative results. Patients who tested positive in the first test would then be given a second test in order to identify any false-positive results.

Dr Timothy Planche, lead author of the study and consultant in medical microbiology at St George's Healthcare NHS Trust, 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."

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