Screening for asymptomatic bacteriuria before total joint arthroplasty

Association not causation

Asymptomatic bacteriuria is associated with an increased risk of both superficial wound infection7 and deep infection after arthroplasty.8 Because a causal link is biologically possible (either through haematogenous spread or direct contamination of the wound), standard orthopaedic practice for arthroplasty patients has included routine preoperative screening for asymptomatic bacteriuria, followed by treatment with oral antibiotics for those who screen positive.

Over the past decade, several prospective studies have investigated the link between asymptomatic bacteriuria and prosthetic joint infection.9 10 11 12 13 However, there remains a lack of good evidence that treating asymptomatic bacteriuria reduces the risk of subsequent prosthetic joint infection. Published studies are all small, with insufficient power to generate convincing results. A trial comparing screening and treatment of asymptomatic bacteriuria with no treatment would require at least 50 000 patients in each arm to detect a difference in infection risk of 0.15% and is therefore, in practice, impossible.14 Bigger and better observational research is still possible, however, and should be a priority.

Sousa and colleagues performed a multivariate analysis adjusting for known risk factors for infection and showed that asymptomatic bacteriuria was associated with a roughly threefold increase in the risk of prosthetic joint infection in patients having hip and knee arthroplasty.8 Of note, the pathogens isolated as a cause of deep prosthetic joint infection are generally different from those detected in the urine of asymptomatic patients preoperatively.15 This suggests that asymptomatic bacteriuria is not a direct cause of prosthetic joint infection. It may instead be an indicator of reduced immune function and increased susceptibility to infection.

Although urine testing is relatively inexpensive, the aggregate costs along with treatment of patients with positive results are substantial. Treating a patient for a urinary tract infection, including urine culture and a primary care appointment, costs about £37 (€45; $50) in the NHS.16 With over 160 000 hip and knee replacements performed annually in the UK, the cost of treating asymptomatic bacteriuria is high. Given the lack of supporting evidence, it is increasingly difficult to justify this practice within cash limited health systems such as the NHS. Indeed, a 2013 international consensus statement from experts in orthopaedic infection stated that routine preoperative urine screening was no longer warranted for patients having elective arthroplasty unless they had a history of, or current symptoms of, urinary tract infection.17

Every precaution must be taken to minimise the potentially devastating effects of prosthetic joint infection. Patients with asymptomatic bacteriuria have an increased risk of infection, but current evidence does not support routine antibiotic treatment before arthroplasty. The practice may contribute to antibiotic resistance, exposes patients to avoidable risk of side effects, and should arguably be abandoned until we have more convincing evidence that it improves outcomes.