Clinical Laboratory Strategies: August 11, 2011
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Implementing POC Creatinine Testing in Radiology

Improved Operational Efficiencies Outweigh Incremental Costs
By Genna Rollins

The need to rapidly assess patients’ kidney function before they undergo radiologic procedures with contrast agents is leading an increasing number of hospitals to implement point-of-care (POC) creatinine tests. Although this method intuitively makes sense, little has been published about its impact on clinical operations or patient disposition. Now, researchers at Massachusetts General Hospital (MGH) in Boston have studied this question, and their findings are examined in this issue of Strategies.

Patients with impaired renal function are at risk for contrast-induced nephropathy and nephrogenic systemic fibrosis when they undergo computed tomography (CT) or magnetic resonance imaging (MRI) with contrast agents. Therefore, it is important to identify them before either procedure, by measuring serum creatinine and calculating estimated glomerular filtration rate (eGFR). However, some patients arrive for CT or MRI without having recent creatinine results or eGFR available in their medical records. As a consequence, a growing number of hospitals have implemented POC creatinine testing in their radiology departments, but few studies have examined how this testing method affects clinical operations or patient disposition. Researchers at MGH recently implemented POC creatinine testing and analyzed both its impact on the radiology department and its overall cost-effectiveness (Clinica Chimica Acta doi:10.1016/j.cca.2011.05.006).

“In general, point-of-care instruments don’t perform as well as those in the central lab. They cost more, and can be more difficult to manage from a regulatory perspective. So the key is if you’re going to implement point-of-care testing, you need to do some kind of ongoing assessment of whether it’s producing the desired effect. Otherwise you can run up a monstrous bill and accomplish nothing,” observed senior author Kent Lewandrowski, MD, associate chief of pathology and director of laboratory medicine at MGH and associate professor of pathology at Harvard Medical School. “Hospitals are very constrained for resources, so for people looking to implement new technologies, it’s important to demonstrate that an effect was produced that justifies all that cost and effort.”

Lewandrowski, who also oversees POC testing at MGH, led the effort to implement POC creatinine in the hospital’s radiology department, which operates six centers and performs monthly nearly 6,000 CT scans with contrast, and about 2,400 MRIs with contrast. “As director of our point-of-care testing program, I’m always looking for ways to implement point-of-care in ways that help improve patient care, the efficiency of care, or that help the hospital manage capacity,” he said. “With radiology, there’s a clear-cut case, with a technology—the creatinine test—and a need. If a patient shows up without a recent creatinine value in their chart, the radiologist has two choices. He or she can either cancel the procedure, then send the patient to have a creatinine test and reschedule the procedure, or do the procedure without contrast, which will provide less information than originally intended. This is all for the want of a simple creatinine on the spot.”

James Nichols, PhD, DABCC, FACB, who was not involved in the study, agreed that the fallout from not having creatinine results available at the time of CT or MRI procedures has prompted many hospitals to implement, or consider implementing, the test as POC. “Hospitals trying to compete in these economic times want to streamline procedures, have the most effective processes, and satisfy patients. So when you have to cancel a procedure because of missing creatinine results you’re not only delaying the procedure, but the rooms are sitting idle, you’re not getting reimbursement, and you’re greatly inconveniencing patients. No one’s going to be happy with such an ineffective practice, so you have to look at the overall effect of integrating that result into the decision-making process.” Nichols is professor of pathology at Tufts University School of Medicine and medical director of clinical chemistry at Baystate Health in Springfield, Mass.

The researchers found that during the 7-month study period, 5.3% of patients—an average of 441 per month—presented for scans without a recent creatinine result or eGFR values. Prior to the POC creatinine implementation, all of these scans either would have been canceled or performed without contrast. An audit of 1 month of eGFR values after implementation of POC creatinine testing showed that 25.8% were abnormal. Of these, 73.7% went on to have scans performed with contrast, and 26.3% without contrast. Of note, 77.8% of patients with an abnormal eGFR had a corresponding creatinine value that was within normal limits (0.6–1.5 mg/dL).

The researchers calculated that each POC creatinine test cost $10.06 versus $5.32 for creatinine testing performed in the central lab, an incremental cost of $4.74 for each POC creatinine test, or $28,154 annually. The authors were unable to completely document expenses associated with CTs or MRIs that initially would have been cancelled because recent creatinine results were not available, such as idle equipment, lost reimbursement, and time involved in rescheduling scans. However, they suggest that “it seems reasonable to assume [these costs] greatly exceed the $4.74 incremental cost of the [POC] test,” thereby making the incremental cost of the POC test “modest” in comparison to improved efficiency and more timely patient care.

Lewandrowski and Nichols agreed that another important aspect of implementing POC creatinine testing is attending to and educating clinicians about analytic differences between POC and central lab analysis for this analyte. MGH implemented an enzymatic POC creatinine test and validated it against a colorimetric Jaffe method used in the central lab, and found the POC test had a slight negative bias for values >2 mg/dL. In contrast, Nichols’s lab observed a slightly positive bias when it validated the same POC method against an enzymatic lab-based method. “If you look in the literature, you can flip a coin. Some are showing high biases, and others are showing low biases. The issue is, they don’t all read the same,” Nichols explained.

He recently wrote about POC creatinine analytical issues for the National Academy of Clinical Biochemistry’s blog. Some POC creatinine tests don’t fully meet recent National Kidney Disease Education Program recommendations, including reporting serum creatinine values as mg/dL to two decimal places. This can lead to some imprecision in eGFR values, but should not discourage hospitals that have other compelling reasons to implement the method from doing so, according to Nichols. “You just have to be aware that it may not give you as good precision as if you calculated eGFR off a lab method. In essence the two will be very close, but if a patient’s eGFR is right around the cutoff, you could have some variability that could push the patient above or below. That’s where the clinician has to make a clinical judgment,” he explained. “As long the physician understands that these methods have variability and doesn’t take the cutoffs as absolutes, there is a place for this type of testing in radiology.”

Nichols also advised that labs need to see that point-of-care and central lab creatinine tests results are distinguished from each other in electronic health records. “You don’t want to see all the creatinines in the same row in the electronic medical record. You want to keep point-of-care and lab-based results separate, because they are different methods and have unique interferences and nuances, like one reporting results to one decimal place and the other reading to two decimal places,” said Nichols.

Lewandrowski agreed that labs need to be aware of these issues, and consider them in the context of any potential benefits of POC testing. “There’s always pushback on point-of-care testing because of the costs associated with it and issues around managing it, but you have to compare it with the alternative,” he said. “With most point-of-care you have to make judgment calls about whether the gains are justified against the potential downsides. In the case of creatinine, they clearly are.”

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Implementing POC Creatinine Testing in Radiology