A unified framework for evaluating the risk of re-identification of text de-identification tools.

OBJECTIVES: It has become regular practice to de-identify unstructured medical text for use in research using automatic methods, the goal of which is to remove patient identifying information to minimize re-identification risk. The metrics commonly used to determine if these systems are performing well do not accurately reflect the risk of a patient being re-identified. We therefore developed a framework for measuring the risk of re-identification associated with textual data releases. METHODS: We apply the proposed evaluation framework to a data set from the University of Michigan Medical School. Our risk assessment results are then compared with those that would be obtained using a typical contemporary micro-average evaluation of recall in order to illustrate the difference between the proposed evaluation framework and the current baseline method. RESULTS: We demonstrate how this framework compares against common measures of the re-identification risk associated with an automated text de-identification process. For the probability of re-identification using our evaluation framework we obtained a mean value for direct identifiers of 0.0074 and a mean value for quasi-identifiers of 0.0022. The 95% confidence interval for these estimates were below the relevant thresholds. The threshold for direct identifier risk was based on previously used approaches in the literature. The threshold for quasi-identifiers was determined based on the context of the data release following commonly used de-identification criteria for structured data. DISCUSSION: Our framework attempts to correct for poorly distributed evaluation corpora, accounts for the data release context, and avoids the often optimistic assumptions that are made using the more traditional evaluation approach. It therefore provides a more realistic estimate of the true probability of re-identification. CONCLUSIONS: This framework should be used as a basis for computing re-identification risk in order to more realistically evaluate future text de-identification tools.

Persistent right aortic arch with an aberrant left subclavian artery, Kommerell's diverticulum and bicarotid trunk in a 3-year-old cat.

CASE SUMMARY: A 3-year-old male, neutered, domestic shorthair cat with a history of chronic regurgitation since being obtained as a kitten was presented for weight loss and regurgitation of all ingested food. The cat was in poor body condition and had a firm swelling in the ventral neck at the time of presentation. Thoracic radiographs showed severe dilation of the entire cervical and cranial intrathoracic esophagus to the level of the heart base. Computed tomographic angiography (CTA) showed a persistent right aortic arch with an aberrant left subclavian artery and severe dilation of the cervical and intrathoracic esophagus cranial to the heart base. CTA also showed a bicarotid trunk and Kommerell's diverticulum to be present, which are rare vascular structures in the cat. Esophagoscopy showed esophageal dilation and multiple compact trichobezoars obstructing the esophagus. Removal of the obstructing trichobezoars resulted in resolution of clinical signs, and the cat was able to drink water and eat a canned food slurry without regurgitation. Surgical correction was not pursued. RELEVANCE AND NOVEL INFORMATION: Vascular ring anomaly (VRA) should be considered in all cats with a history of regurgitation, regardless of their age at the time of presentation. CTA is a valuable diagnostic imaging procedure that allows differentiation of a VRA from other causes of esophageal obstruction and provides information about the VRA that can be used to determine amenability to surgical correction.

Secure surveillance of antimicrobial resistant organism colonization or infection in Ontario long term care homes.

BACKGROUND: There is stigma attached to the identification of residents carrying antimicrobial resistant organisms (ARO) in long term care homes, yet there is a need to collect data about their prevalence for public health surveillance and intervention purposes. OBJECTIVE: We conducted a point prevalence study to assess ARO rates in long term care homes in Ontario using a secure data collection system. METHODS: All long term care homes in the province were asked to provide colonization or infection counts for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and extended-spectrum beta-lactamase (ESBL) as recorded in their electronic medical records, and the number of current residents. Data was collected online during the October-November 2011 period using a Paillier cryptosystem that allows computation on encrypted data. RESULTS: A provably secure data collection system was implemented. Overall, 82% of the homes in the province responded. MRSA was the most frequent ARO identified at 3 cases per 100 residents, followed by ESBL at 0.83 per 100 residents, and VRE at 0.56 per 100 residents. The microbiological findings and their distribution were consistent with available provincial laboratory data reporting test results for AROs in hospitals. CONCLUSIONS: We describe an ARO point prevalence study which demonstrated the feasibility of collecting data from long term care homes securely across the province and providing strong privacy and confidentiality assurances, while obtaining high response rates.