Guidance from NICE on stopping antibiotic prophylaxis before invasive procedures in patients at risk has not resulted in an increase in cases of infective endocarditis.

In March 2008, NICE released new guidance on the role of antibiotic prophylaxis in the prevention of infective endocarditis. This caused quite a stir as it proposed a radical shift in clinical practice by suggesting that such prophylaxis, before dental and other invasive procedures, should be stopped. Furthermore, it was not based on any new evidence. It had been accepted practice to recommend antibiotic prophylaxis before potentially bacteraemic procedures for patients with underlying cardiac conditions which could result in turbulent blood flow such as valve disease and congenital defects.

Despite the initial furore this guidance has generally been adopted and a recent study in the BMJ set out to investigate its impact. The authors stated aim was to quantify the change in prescribing of antibiotic prophylaxis before invasive dental procedures for those at risk of infective endocarditis, and any concurrent change in the incidence of infective endocarditis following the introduction of the NICE guidance.

The authors examined the monthly number of prescriptions, in England, for antibiotic prophylaxis consisting of a single 3 g oral dose of amoxicillin or a single 600 mg oral dose of clindamycin, between January 2004 and April 2010.

They looked at all cases admitted to hospital in England with a primary or secondary discharge diagnosis of acute or subacute infective endocarditis from January 2000 until April 2010. Figures for the monthly number of cases of infective endocarditis, infective endocarditis related deaths in hospital, or cases of infective endocarditis with a possible oral origin for streptococci were also obtained.

The results showed that following the introduction of the NICE guidance there was a highly significant 78.6% reduction (p<0.001) in the prescribing of antibiotic prophylaxis, from a mean of 10,277 prescriptions per month to 2,292. They also found that despite a general upward trend in the number of cases of infective endocarditis before the guidance that there was no significant change in this trend after the guidance was introduced (p=0.61).

The authors therefore concluded that despite a huge reduction in the prescribing of antibiotic prophylaxis that there had been no large increase in the incidence of cases of, or deaths from, infective endocarditis in the two years following publication of the guidance.

This would seem to support NICE and silence the critics, of which I was one, but it should be remembered that we must continue to monitor the situation as trends may appear over time.

There is also a need for robust trials to determine if prophylaxis protects those patients considered to be at particularly high risk such as those with: a previous history of infective endocarditis; prosthetic cardiac valves; a cardiac transplant and valve disease and certain congenital defects.

Dr Peter Savill

• Thornhill MH, Dayer MJ, Forde JM et al. Impact of the NICE guideline recommending cessation of antibiotic prophylaxis for prevention of infective endocarditis: before and after study. BMJ 2011;342:d2392