A-397 Creatinine Chaos: When Numbers Fail, Imaging Freezes

Abstract

Background: As chronic disease rates rise, intravenous (IV) contrast usage for diagnostic imaging is increasing steadily. While IV procedures are largely safe, patients at risk of contrast-induced neuropathy (CIN) due to predisposing factors like renal disease, albuminuria, diabetes, or nephrotic medications need pre-IV renal assessments. Widely used frontline point-of-care creatinine (POC) screening tests can yield ambiguous results, leading to retests, delays, patient distress, and healthcare burdens. This case study illustrates the consequences of unexpected elevation in initial POC creatinine (Cr) result on IV contrast plans, and examines how a holistic, patient-centric approach can alleviate renal concerns and enable timely imaging procedures Case Presentation: A diabetic, hypertensive, and chronic kidney diseased Caucasian male, aged 61, presented for a scheduled intravenous contrast-enhanced computed tomography scan. His initial POC-based Cr result of 1.20 mg/dL narrowly exceeded the reference interval (RI) (0.67 - 1.17 mg/dL). Given the patient’s pre-existing conditions, this increment raised the patient’s anxiety and laboratory-based Cr test was performed to reassure his renal function. The new result was found to be 0.95 mg/dL (RI: 0.72 -1.25 mg/dL), which fell within the normal RI. The 0.25 mg/dL (20.8%) disparity between Cr tests, which delayed the IV procedure, led the clinician to request a thorough laboratory investigation to assess the clinical significance of these fluctuations. Diagnostic Challenge: This case is notable for its distinctive presentation. Despite the patient*s underlying conditions, his Cr levels remained within normal range over the past 12 years, with only slight decrease observed on occasion. The recent pre-IV contrast renal assessment marked the first unexpected rise in Cr levels, making it an interesting case for in-depth analysis. Our examination of Cr results and its curvilinear relationship with kidney function limited the relevance of using population-based reference intervals (PBRI) in this patient. Results/Investigation and Outcome: Subject-based reference intervals (SBRI) were calculated using the index of individuality (IOI) and relative change value (RCV). The laboratory-based Cr assay showed an IOI of 0.271 and RCV of 17.3%, while the POC device yielded an IOI of 0.49 and RCV of 31.4%. The resulting SBRI ranges were 0.67-0.95 mg/dL for the laboratory method and 0.56-1.07 mg/dL for the POC assay. The latest lab-based Cr result (0.95 mg/dL) was within the SBRI range, while the POC result (1.2 mg/dL) exceeded the upper limit by 12%. Although the 20.8% discrepancy between methods exceeded the 15% total allowable error (TAE), the absolute difference of 0.25 mg/dL remained within the 0.3 mg/dL regulatory guideline. Conclusions/Clinical Implications: This case underscores the challenges of unexpected overestimation of POC Cr results, which can lead to patient distress and procedural delays during pre-IV contrast renal assessments. By incorporating patient-centric estimates such as IOI, RCV, SBRI, and TAE, we foster evidence-based, individualized decision-making. In addition to serving as a valuable educational resource for clinical fellows, trainees, and professionals on the application of patient-centered metrics in clinical decision, our approach offers a structured pathway to refine and expedite IV contrast eligibility workflows.