Results reporting in microbiology: What’s needed, what’s not?

Create PDF

Ann Griswold, PhD

After the patient specimens have been collected and the tests have been performed, after the legwork is complete and the results are in hand, reporting clinical microbiology findings should in theory be the easy part—the final step before an effective treatment plan is formed. But as any seasoned clinical microbiologist knows, that couldn’t be further from the truth.

“There has always been an age-old challenge in what results the microbiology laboratory should report,” says David W. Craft, PhD D(ABMM), microbiology medical director at the Milton S. Hershey Medical Center and an associate professor of pathology at Pennsylvania State College of Medicine. “Unlike other departments in the clinical laboratory—hematology and chemistry, for example—we produce a lot of positive results that shouldn’t be acted on.”

How test results are reported—and whether microbiology reports include commensal organisms or other information that may or may not be clinically significant—can have dramatic consequences for patient care. A test report can muddle the conversation about appropriate treatments, or it can save a patient’s life. And with the advent of new, high-throughput technologies, results that were difficult to report in the past have become even more challenging.

“We now have new methods coming along that produce a lot more information, and not just more information but different types of information,” Dr. Craft says. In years past, microbiology tests simply detected how many and which bacteria were present. Now they do that and more. “We have new technologies like MALDI TOF, which give us chemical libraries, and sequencing, which gives us sequencing databases, and all of that comes with information requests, and again, questions about clinical significance.”

Here, four seasoned microbiologists share their perspectives on clinical test reporting strategies: what results are appropriate to report, how best to report them, and how laboratory test reporting strategies can promote the best possible patient care outcomes.

When it comes to microbiology test result reporting, says Dr. Craft, islands of consensus exist, but between these islands is a great sea of variability.

“There are well-described and defined protocols for the historical problem: dealing with growing commensal organisms that perhaps aren’t of clinical significance,” he says. Plenty of references exist, such as the Clinical Microbiology Procedures Handbook and diagnostic textbooks. But while organisms may be worked up similarly from laboratory to laboratory, he notes, there are clear differences in how organisms are worked up for certain patient populations. Adding to that concern, none of the new high-throughput technologies are well described or standardized with respect to clinical test result reporting.

This can give rise to apparent discrepancies when patients are transferred from one hospital to another. “We might get a patient here at Hershey Medical Center who was worked up in a local community hospital and perhaps referred here because of a complicated case,” says Dr. Craft. “In looking at the microbiology data from the previous hospital, I might see things that seem to be in conflict with how I do my lab work.” The previous laboratory, for example, might have grown an organism that it assumed was clinically insignificant and, as a result, it might have foregone antibiotic susceptibility testing. “I might, on the other hand, say, ‘No, I think that is clinically significant.’ I might do a full identification, confirm what the organism is, and do testing for susceptibility predictions so that the patient can get on the right therapy.”

Neither laboratory is technically wrong, Dr. Craft says. “Each of us made different decisions based on what we thought the clinical staff would need to do.” In most cases, these discrepancies reflect differing perspectives or approaches; rarely do they reflect error.

Dr. Craft

In the heat of the moment, however, it’s sometimes difficult to appreciate such differences. A few years ago, Dr. Craft’s laboratory received a Saturday morning call from an out-of-state clinician who requested urine culture results for a patient who had visited the ER while on vacation. “The laboratorian reported the results as greater than 100,000 CFUs of coagulase-negative staphylococci, to which the clinician responded, ‘Thank you. Have you done the susceptibility testing on that yet?’ Our laboratory folks correctly said, ‘We don’t routinely perform susceptibilities on coagulase-negative staphylococci in the urine.’ The clinician responded, ‘Well, that’s not how we practice medicine in this state. In our hospital, technicians don’t tell MDs what to do. We tell the technicians what to do.’”

The laboratorian, Dr. Craft’s senior technician at the time, asked if the clinician wanted to speak with the laboratory director, who could be contacted easily on weekends. The clinician did not. The senior technician agreed to run the susceptibility testing, told the clinician the results would be available the next day, and asked for the best phone number to call.

There are two lessons to this story, Dr. Craft notes. The first is that some test results are simply not significant, and it’s not always obvious to non-microbiologists what is and isn’t relevant. “This is a result we routinely don’t put a lot of clinical significance into, and our medical staff here agrees. I would not grow this organism from someone’s urine and assume they had a bladder or kidney infection. We would assume it was skin contamination, and therefore we wouldn’t do a workup and we wouldn’t do susceptibility testing.” That doesn’t rule out special circumstances. “If urology or infectious disease called about a complicated patient, and they really wanted the susceptibility testing, I’m happy to do it,” he notes. “But my standard algorithm is, we won’t do that unless requested.”

The second lesson is that antagonistic relationships between clinical staff and laboratory staff reflect an important divide in the laboratory community. “How aggressive should we be in thinking for the physicians, and making comments in our reports that may drive therapy?” Dr. Craft asks. The balance between providing therapeutic guidance and remaining strictly interpretive is a difficult one. Should laboratories make sure clinicians understand the microbiology and assume they know how to treat difficult organisms? Or should laboratories assume that clinicians may not know how to treat some of the more difficult or rare organisms, and report based on those assumptions?

The answer is far from straightforward and steeped in controversy. When Dr. Craft posted an informal survey on the American Society for Microbiology’s listserve, he received about 40 responses, divided almost equally between those who felt that interpretive comments were warranted but therapeutic suggestions were solely the clinician’s responsibility, and those who felt that clinical microbiologists are more informed than clinicians about the therapeutic implications of certain microbiology test results and therefore obligated to make recommendations.

“At either end of the spectrum, there’s some polarization,” Dr. Craft says. “It’s really interesting, and it suggests to me that our clinical microbiology directors have fallen into a number of different categories in terms of where they think we should be.”
Susan Sharp, PhD, D(ABMM), FAAM, says microbiologists shouldn’t expect clinicians to be experts in clinical microbiology, nor should they be afraid to share their knowledge with clinicians so clinicians can use it to help care for their patients.