To the Editor: While agreeing that sensible utilisation of pathology tests in emergency departments (EDs) is important, we are concerned that the article by Stuart et al1 might be misinterpreted to justify wholesale reductions in important diagnostic microbiological tests, particularly blood cultures. Stuart and colleagues imply they could safely reduce the number of blood cultures by 80%.1 Other local data have suggested a minority of blood cultures in the ED influence patient management.2

Confirmation of aetiology will be denied for patients by "rationalisation" of blood cultures in EDs. Although most pathogens are susceptible to broad-spectrum anti-microbial agents, widespread empiric prescribing of such agents in an era of increasing antimicrobial resistance is unwise.

A recent Australian study evaluating blood cultures found that a third of patients with positive blood culture results were not clinically suspected to be bacteraemic.3 Furthermore, the Journal recently reported the emergence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA),4 and increasing resistance in Streptococcus pneumoniae.5 Missing MRSA or multidrug-resistant pneumococcal bacteraemia will result in adverse patient outcomes. What about missed cases of meningococcal disease, or typhoid fever, with their associated public health costs? Paradoxically, amid emerging antimicrobial resistance, we may become less aware of the problem. Furthermore, what about the infection control costs required to control the resultant outbreaks of multidrug-resistant organisms?

Empiric broad-spectrum antibiotic prescribing, driven by failure to undertake important microbiological investigations, is bad medicine:

• It teaches everyone to guess the microbiological diagnosis, and, if you do not test, who can prove you wrong? Perhaps only when the patient presents to the tertiary referral hospital with therapeutic failure and evolving multisystem organ failure.

• It logically extrapolates to all patients getting vancomycin plus meropenem to ensure covering MRSA and resistant gram-negative bacilli.

• It inevitably drives resistance, which is increasing rapidly.

• It has never been subject to rigorous scientific scrutiny with cost-effectiveness studies.

Moreover, the study by Stuart et al1 provides no data on readmission rates, lengths of stay, adverse events and rates of missed or incorrect diagnoses; the ED setting studied has limited generalisability; and United States guidelines, which may be inappropriate in the Australian healthcare context, were used to develop the diagnostic testing protocol.

Might not reducing the ordering of some microbiological tests cause "spiralling therapeutic empiricism"? Might not the overall healthcare budget growth accelerate because of increased prescribing of expensive broad-spectrum antimicrobials?