Privacy preserving linkage using multiple match-keys.

INTRODUCTION: Available and practical methods for privacy preserving linkage have shortcomings: methods utilising anonymous linkage codes provide limited accuracy while methods based on Bloom filters have proven vulnerable to frequency-based attacks. OBJECTIVES: In this paper, we present and evaluate a novel protocol that aims to meld both the accuracy of the Bloom filter method with the privacy achievable through the anonymous linkage code methodology. METHODS: The protocol involves creating multiple match-keys for each record, with the composition of each match-key depending on attributes of the underlying datasets being compared. The protocol was evaluated through de-duplication of four administrative datasets and two synthetic datasets; the 'answers' outlining which records belonged to the same individual were known for each dataset. The results were compared against results achieved with un-encoded linkage and other privacy preserving techniques on the same datasets. RESULTS: The multiple match-key protocol presented here achieved high quality across all datasets, performing better than record-level Bloom filters and the SLK, but worse than field-level Bloom filters. CONCLUSION: The presented method provides high linkage quality while avoiding the frequency based attacks that have been demonstrated against the Bloom filter approach. The method appears promising for real world use.

Evaluation of approximate comparison methods on Bloom filters for probabilistic linkage.

INTRODUCTION: The need for increased privacy protection in data linkage has driven the development of privacy-preserving record linkage (PPRL) techniques. A popular technique using Bloom filters with cryptographic analyses, modifications, and hashing variations to optimise privacy has been the focus of much research in this area. With few applications of Bloom filters within a probabilistic framework, there is limited information on whether approximate matches between Bloom filtered fields can improve linkage quality. OBJECTIVES: In this study, we evaluate the effectiveness of three approximate comparison methods for Bloom filters within the context of the Fellegi-Sunter model of recording linkage: Sørensen-Dice coefficient, Jaccard similarity and Hamming distance. METHODS: Using synthetic datasets with introduced errors to simulate datasets with a range of data quality and a large real-world administrative health dataset, the research estimated partial weight curves for converting similarity scores (for each approximate comparison method) to partial weights at both field and dataset level. Deduplication linkages were run on each dataset using these partial weight curves. This was to compare the resulting quality of the approximate comparison techniques with linkages using simple cut-off similarity values and only exact matching. RESULTS: Linkages using approximate comparisons produced significantly better quality results than those using exact comparisons only. Field level partial weight curves for a specific dataset produced the best quality results. The Sørensen-Dice coefficient and Jaccard similarity produced the most consistent results across a spectrum of synthetic and real-world datasets. CONCLUSION: The use of Bloom filter similarity comparisons for probabilistic record linkage can produce linkage quality results which are comparable to Jaro-Winkler string similarities with unencrypted linkages. Probabilistic linkages using Bloom filters benefit significantly from the use of similarity comparisons, with partial weight curves producing the best results, even when not optimised for that particular dataset.

Cervical paragangliomas: single centre experience with 44 cases.

Paragangliomas (PGL) are rare lesions of the neuroendocrine system; in the neck, they usually affect the carotid glomus (carotid body tumours-CBT). This retrospective analysis reports our experience in management of these lesions in patients treated by surgical resection. Between 2000 and 2014, 33 patients were surgically treated at our institution, obtaining a series of 44 cervical PGLs. Tumour characteristics, family history, diagnostic procedures, surgical treatment, short- and long-term outcomes were reviewed. A female prevalence was found (76% of cases). Familial cases occurred in 9 patients (20%); 6 presented with bilateral lesions and 1 had multiple paragangliomas. Lymph node metastasis was not found in any patient. All lesions were classified into three groups according to the latero-lateral diameter. Complete resection of the PGL was performed in all patients. Mortality was null; transitory cranial nerve deficit occurred in 20% of cases with permanent palsy in 6.7%. No perioperative stroke/TIA were observed. Surgical resection of PGL should be considered as the only therapeutic option because it can ensure complete removal of the disease. Patients with bilateral lesions and positive family history should be referred for genetic analysis. Preoperative planning of the surgical procedure by integrated diagnostic imaging and a full mastery of vascular surgery techniques are mandatory to minimise the risk of the most common postoperative complications. Long-term follow-up is recommended, particularly in patients with familial disease or sporadic lesions treated in an advanced stage.

Urokinase and AT-III concentrate treatment in inferior vena cava thrombosis associated with nephrotic syndrome.

A patient with an inferior vena cava thrombosis in nephrotic syndrome was treated with heparin, AT-III concentrates and urokinase. After a few days on treatment he showed a complete resolution of the thrombosis. We suggest that this therapeutic combination may be a good approach to the treatment of thrombosis in nephrotic syndrome.

Syphilitic aneurysm of the abdominal aorta.

A case of syphilitic aneurysm of the abdominal aorta is described. This unusual finding may be misdiagnosed as "inflammatory" abdominal aortic aneurysm, another condition associated with an intense periaortic inflammatory reaction. The authors discuss the differential diagnostic problems and the surgical technique advisable in these cases.

A linkage study of Western Australian drink driving arrests and road crash records.

Records of drivers in all reported road crashes occurring in Western Australia between 1987 and 1995 were linked with records of all drink driving arrests in the same period. About 7% of all drink driving arrests occurred because of a road crash. Differences were observed between these drink-driving crashes and other types of road crashes. Drink driving crashes tended to be more severe than those not involving alcohol. Serious crashes (involving fatalities or hospitalisations) accounted for 20% of alcohol-related crashes, but only 6% of all crashes reported over the study period. From another perspective, crash-related drink-driving arrests were more likely than routine enforcement arrests to involve younger (18-35 years) and older (65 years and over) drink drivers. Routine enforcement arrests, on the other hand, were likely to involve a greater proportion of Aboriginal drivers.

Novice drink drivers, recidivism and crash involvement.

A group of drink drivers with no prior arrest for drink driving was selected from drink driving arrest records originating in Western Australia between 1987 and 1995. These drink-driving records were linked to road crash records for the same period. The analysis of these combined records focussed on the sequence of driving events (i.e., arrests, crashes and arrests resulting from crashes) and the present article explores the relationship in time between known drink driving incidents and crash involvement. Using multi-variate survival analysis, it was found that if a driver's first drink driving offence resulted from a road crash, especially if this occurred at a younger age, he/she was significantly more likely to drink, drive and crash again.

The construction of a road injury database.

In order to effectively examine possible causes and determinants of road trauma, reliable information on the participants, circumstances, and resultant injuries and deaths must be available. Characteristics of participants (persons and vehicles) and the circumstances of road accidents are routinely collected by police and road authorities, whereas details of the injuries and medical care provided to casualties are collected by hospital and ambulance services. A road injury database, linking data collected by the Health, Police, and Main Roads Departments of the Government of Western Australia with records of the St. John Ambulance Association and the Death Register, has been established. This paper describes the procedures used to link the various sources of data and discusses the design, construction, and quality of the resultant relational database.

Digestive and nutritional consequences of pancreatic resections. The classical vs the pylorus-sparing procedure.

Digestive and nutritional alterations are a common occurrence after pancreatic resections. The authors report the results of a multiparametric evaluation performed in a group of 26 patients submitted to total or cephalic pancreatectomy. Patients were divided into two groups according to the surgical procedure; group A (n = 13) included gastroresected patients and group B (n = 13) included those submitted to pylorus-sparing pancreatic resection. Subclinical digestive and absorptive impairment has been found in 61.5% of group A patients; the nutritional status was clinically poor in four cases from the same group. Digestive alterations have also been found in 69.2% of group B cases, but nutritional status was always satisfactory in the whole group. The more positive results obtained with the pylorus-sparing technique encourage wider adoption of this procedure.

Duodenal malignant somatostatinoma.

The authors report a case of hormonally silent duodenal somatostatinoma. The main clinical features, the natural history and the currently available therapies of these rare neoplasms are described on the basis of this case and of the scientific literature. Although the antiblastic therapies are still debated, the patient showed a surprising outcome following chemotherapy.

Carcinoma of the pancreas: a personal experience with 100 cases.

One hundred patients with pancreatic cancer were evaluated between March 1981 and December 1989. This study showed that 61 were not candidates for definitive surgery because of nonoperability (28 patients) or nonresectability (33 patients). An additional 25 patients had cancers that were unresectable because of metastases (13 patients) or local spread of disease (12 patients) discovered at laparotomy. Fourteen patients had resectable cancers. Ten were treated by total pancreatectomy, three by distal pancreatectomy and one by pancreatoduodenectomy (Whipple). There were two operative mortalities. The median patient survival time was 20.5 months. Two patients survived 5 years. Five patients are alive at 3, 14, 18, and 47 months. Palliative surgical procedures performed in 18 patients included 10 biliary bypasses, 9 gastrojejunostomies, and 6 T-tube placements. This was associated with an operative mortality rate of 11%. The median survival time was 5 months. Other palliative measures included endoscopic placement of biliary and pancreatic stents (47 patients, 2.7% mortality rate), endoluminal radiation therapy, interstitial radiation therapy and external beam radiation therapy. The median survival time of patients so treated was 4.5 months.