Reimbursement Policies for Carotid Duplex Ultrasound that are Based on International Classification of Diseases Codes May Discourage Testing in High-Yield Groups

Abstract

Background: To curb increasing volumes of diagnostic imaging and costs, reimbursement for carotid duplex ultrasound (CDU) is dependent on "appropriate" indications as documented by International Classification of Diseases (ICD) codes entered by ordering physicians. Historically, asymptomatic indications for CDU yield lower rates of abnormal results than symptomatic indications, and consensus documents agree that most asymptomatic indications for CDU are inappropriate. In our vascular laboratory, we perceived an increased rate of incorrect or inappropriate ICD codes. We therefore sought to determine if ICD codes were useful in predicting the frequency of abnormal CDU. We hypothesized that asymptomatic or nonspecific ICD codes would yield a lower rate of abnormal CDU than symptomatic codes, validating efforts to limit reimbursement in asymptomatic, low-yield groups.

Material and methods: We reviewed all outpatient CDU done in 2011 at our institution. ICD codes were recorded, and each medical record was then reviewed by a vascular surgeon to determine if the assigned ICD code appropriately reflected the clinical scenario. CDU findings categorized as abnormal (>50% stenosis) or normal (<50% stenosis) were recorded. Each individual ICD code and group 1 (asymptomatic), group 2 (nonhemispheric symptoms), group 3 (hemispheric symptoms), group 4 (preoperative cardiovascular examination), and group 5 (nonspecific) ICD codes were analyzed for correlation with CDU results.

Results: Nine hundred ninety-four patients had 74 primary ICD codes listed as indications for CDU. Of assigned ICD codes, 17.4% were deemed inaccurate. Overall, 14.8% of CDU were abnormal. Of the 13 highest frequency ICD codes, only 433.10, an asymptomatic code, was associated with abnormal CDU. Four symptomatic codes were associated with normal CDU; none of the other high frequency codes were associated with CDU result. Patients in group 1 (asymptomatic) were significantly more likely to have an abnormal CDU compared to each of the other groups (P < 0.001, P < 0.001, P = 0.020, P = 0.002) and to all other groups combined (P < 0.001).

Conclusions: Asymptomatic indications by ICD codes yielded higher rates of abnormal CDU than symptomatic indications. This finding is inconsistent with clinical experience and historical data, and we suggest that inaccurate coding may play a role. Limiting reimbursement for CDU in low-yield groups is reasonable. However, reimbursement policies based on ICD coding, for example, limiting payment for asymptomatic ICD codes, may impede use of CDU in high-yield patient groups.