Use of CT (computed tomography) in a Medicare population

Research objective:

Rising use of CT has led to much concern recently regarding the radiation risks to patients due to the cumulative exposure. Our study objective is to measure the extent to which patients get multiple CTs in a two-year period, and to investigate the factors that influence the probability of having multiple images.

Data and Methods :

Using the Medicare 5% Limited Dataset for 2003-2004, we analyze claims for CT utilization, overall and by medical condition to measure the number of CTs performed on the same patient during the two year period. For each patient, we will identify characteristics of (a) treating physicians, (b) county of residence, (c) place of service, and (d) patient. For each condition, logistic regression analysis will be used to measure the effect of each variable of interest on the odds of having multiple CTs.

Principal findings:

Preliminary analysis on patients with respiratory illnesses in the Medicare 2004 data show that overall, 28% of patients have 2 or more CTs and a little over 10% have 3 or more CT during the year. The percent of patients with 3 or more CT is slightly higher in the inpatient setting (12.5%) than in offices (10%), hospital outpatient departments (9.8%), and emergency rooms (4%). But as many as 18% of patients in the emergency room for respiratory illnesses have more than one CT.

On claims for these patients, 23% have more than 1 chest CT, and 6% of patients had 3 or more. Claims for lower respiratory disease, pleurisy/pneumothorax, and COPD were more likely to result in multiple CTs than other respiratory diagnoses. There is little variation by age, race, and gender on percent of patients with multiple CTs.

Conclusions:

Preliminary findings point to the existence of patients who may be at elevated risks of radiation effects from CT imaging. We expect that analysis will reveal which characteristics most influence the odds of a patient having multiple CTs for a condition.

Implications for policy, delivery, and practice:

The results of this study will help policy makers and health care providers to 1) identify conditions and situations if any, where more exploration may be needed to evaluate if the use of multiple CT images is consistent with best practices, and (2) identify specific groups of providers and patients, who may need education on the potential risks of radiation when considering having a CT.