Promoting Diagnostic Stewardship

Ensuring clinically relevant microbiology results

September 5, 2019

Our duty of care is to do no harm

Contributed by:

Dr. Shobhana Kulkarni (Click for bio)

Case

Consider the following scenario and how it can lead to patient harm:

An 80-year-old afebrile, hemodynamically stable woman is seen in the emergency department for acute onset confusion. She has not been eating or drinking well for the last few weeks. On examination, she is dehydrated. She has a long-term indwelling catheter in situ and her urine is cloudy and foul smelling.

The physician sends a urine specimen for culture to rule out infection.

The relevant clinical information (symptoms, signs and risk factors for requesting the test) is not provided on the microbiology requisition. Culture grows 10⁸ cfu/L mixed growth of Escherichia coli and Enterococcus faecalis and susceptibilities are reported. The patient, who has since improved following rehydration, is started on antimicrobials to treat the positive culture result.

Background

This case demonstrates the low threshold that clinicians have for requesting urine culture, which is often inappropriate, especially in the elderly with non-specific signs or symptoms. Requests for culture from body sites that are commonly colonized with commensal bacteria have a high likelihood of false positive results and, in this case are due to colonization of the catheter or asymptomatic bacteriuria. Physicians often act by prescribing antimicrobials, potentially leading to patient harm from unnecessary drug adverse effects (including diarrhea due to Clostridioides difficile), which can increase rates of antimicrobial resistance. It is an unwise use of finite and valuable health care resources.

Misuse of laboratory tests is a common problem, which needs a multi-pronged approach to solve. Providing education and easy-to-use tools for physicians and other health care workers is important. A yet unexplored approach is to require ordering physicians to provide sufficient clinical information to the laboratory physician. This ensures the lab physician may appropriately process the specimen and interpret the results, so providing a clinically relevant result. This is not only about reducing unnecessary tests but would be equally advantageous for tests that are appropriately ordered.

The College of Physicians & Surgeons of Alberta considers sending a specimen to the laboratory physician to be a consultation. Therefore, an ordering physician is required to provide the clinical information on the requisition.

Diagnostic stewardship, i.e., the process of laboratories providing clinically relevant (patient-centered) results, is increasingly recognized as a vital part of antimicrobial stewardship.¹ However, this is possible only if the laboratory physician is provided with the relevant clinical information; analogous to a cardiologist interpreting an electrocardiogram or a radiologist interpreting a chest X-ray. Regrettably, compliance with provision of relevant clinical information on microbiology requisitions is poor.

Back to the case: The preferred outcome

Despite this patient’s change in mental status and the cloudy, foul urine, a urinary tract infection is excluded as a cause due to the absence of localizing urinary symptoms, fever or sepsis. Dehydration is the likely cause for her non-specific changes and urine culture was not indicated. Rehydration and close observation would be best practice.²

Urine culture would be indicated only if there was no improvement after 24 hours with no other evident cause or if she developed localizing urinary symptoms, fever or sepsis. In this event, urinalysis should also be ordered. Absence of pyuria by dipstick and microscopy would make UTI very unlikely, even with a positive culture.

If urine culture was ordered anyway, ideally the clinician would have provided the relevant clinical information on the requisition including: Confused. Dehydrated. Long-term indwelling catheter in situ. Urine is cloudy and offensive.

Provided with this information the laboratory would have reported the result as follows:

Clinically relevant result: 10⁸ cfu/L E.coli, 10⁸ cfu/L E.faecalis. Susceptibilities provided.
Please note: Unless there is a clinical diagnosis of UTI (e.g., dysuria, frequency or non-localizing symptoms/signs, e.g., fever, sepsis with no other cause), this result most often represents asymptomatic bacteriuria (ASB). Antibiotics are not indicated for ASB except during pregnancy or prior to any urological procedure likely to cause mucosal bleeding. Changes in mental status or character of urine without localizing urinary symptoms are not diagnostic of infection.

Upon reading this report, presumably the clinician would have then not started antibiotics.

A change in practice is needed

If we are to provide better patient care and safety, promote good antimicrobial stewardship and use our finite health care resources wisely through appropriate test utilization, clinicians need to promote diagnostic stewardship by providing relevant clinical information every time a test is ordered. This will ensure the goals supported by Choosing Wisely Canada² and the Canadian Medical Protective Association are achieved.

Bottom line

• Order tests only if the result will change patient management.
• Use available resources to aid best practice, including consulting the microbiologist on call, laboratory guide to services and expert guidelines.
• Provide the relevant clinical information (symptoms, signs and risk factors prompting the request) on the test requisition so the result is clinically relevant and patient-centered. This information can also be documented in the patient’s chart as a record of why the test was ordered.
• Collect and transport specimens correctly since the quality of the specimen received in the laboratory will influence the accuracy of the result.
• Correlate the result with the patient’s clinical state and start appropriate antimicrobials only if clinically indicated.
• Read laboratory comments, if present, since they aid result interpretation.

References

1. 1. Morgan DJ, Malani P, Diekema DJ. Diagnostic Stewardship—Leveraging the Laboratory to Improve Antimicrobial Use. JAMA. 2017;318(7):607-608
   2. www.choosingwiselycanada.org