CODIFI2: Randomised controlled trial of swab versus tissue sampling for infected diabetic foot ulcers

Project Description

Up to 1 in 4 people with diabetes will develop a foot ulcer related to their diabetes. Some ulcers become infected with bacterial, leading to pain, redness and delayed ulcer healing. If infection spreads it damages skin and bone in the foot and this can require surgery to remove infected tissues. Doctors, nurses and podiatrists are vigilant for any signs of infection and act quickly to clear the ulcer of infection, including prescribing antibiotics to fight the infection.

When infection is suspected the nurse or podiatrist will collect a specimen from the wound to send to a laboratory to identify the bacteria causing the infection. There are two ways to collect a wound sample: collecting would fluid using a cotton swan (wound swab), or taking a small piece of wound tissue (tissue sample). Swabs are easier and this method is used the most. Many experts and practice guidelines recommend tissue sampling as it is better as collecting harmful bacteria. Previous studies have found tissue samples collect more bacterial than swabs, but also that swabs are less painful. Now that we know tissue samples collect more bacteria, we want to test whether this information helps clinicians make better decisions about which antibiotics to use. We will also see whether this helps clinicians better match the antibiotics to the infection, and so cure the infection and help the ulcer heal more quickly.

To make a fair comparison of swab versus tissue sampling we will recruit 730 people with diabetic foot ulcer infection. The nurse or podiatrist will obtain a wound specimen by swab or tissue sample, as allocated by a computer. The doctors, nurses and podiatrists will decide on all aspects of each patients care, such as dressings, off-loading and any medications. We will follow these patients and collect information on their treatment, the ulcer infection, and the size of the ulcer (until the ulcer heals or 1-2 years later). All samples will be sent to the local laboratory to be frown and tested to see what antibiotics will work. We won’t include people with severe infection, anyone unable to consent or those with very old ulcers (more than 2 years). We will follow-up patients at 4 weeks & at 6 months to see if their ulcer is reducing in size: and visit patients when their ulcer has healed. We will collect information on the ulcer, their overall health, and the treatments and care they have had for their foot ulcer, using a postal questionnaire and from hospital notes.

We will take a 2nd wound sample to test for bacteria using genetic “fingerprinting” techniques that look for bacteria DNA. This will tell us whether these tests find more bacteria that growing them in the laboratory, and if so, would this potentially change antibiotic treatment. The microbiology reports obtained from the molecular techniques will be used to discuss with clinicians in interview how they would use the detailed information and whether they would replace traditional techniques with the modern methods, or prefer to use both. The information obtained from the molecular techniques will be investigated to see if it helps us predict ulcer healing better than the factors we already know are important (e.g. large ulcers take longer to heal than small ulcers).

During CODIFI2 we will also study the impact of the letters asking people to complete postal surveys on completion rates.