Privacy-preserving record linkage across disparate institutions and datasets to enable a learning health system: The national COVID cohort collaborative (N3C) experience

Introduction

Research driven by real-world clinical data is increasingly vital to enabling learning health systems, but integrating such data from across disparate health systems is challenging. As part of the NCATS National COVID Cohort Collaborative (N3C), the N3C Data Enclave was established as a centralized repository of deidentified and harmonized COVID-19 patient data from institutions across the US. However, making this data most useful for research requires linking it with information such as mortality data, images, and viral variants. The objective of this project was to establish privacy-preserving record linkage (PPRL) methods to ensure that patient-level EHR data remains secure and private when governance-approved linkages with other datasets occur.

Methods

Separate agreements and approval processes govern N3C data contribution and data access. The Linkage Honest Broker (LHB), an independent neutral party (the Regenstrief Institute), ensures data linkages are robust and secure by adding an extra layer of separation between protected health information and clinical data. The LHB's PPRL methods (including algorithms, processes, and governance) match patient records using "deidentified tokens," which are hashed combinations of identifier fields that define a match across data repositories without using patients' clear-text identifiers.

Results

These methods enable three linkage functions: Deduplication, Linking Multiple Datasets, and Cohort Discovery. To date, two external repositories have been cross-linked. As of March 1, 2023, 43 sites have signed the LHB Agreement; 35 sites have sent tokens generated for 9 528 998 patients. In this initial cohort, the LHB identified 135 037 matches and 68 596 duplicates.

Conclusion

This large-scale linkage study using deidentified datasets of varying characteristics established secure methods for protecting the privacy of N3C patient data when linked for research purposes. This technology has potential for use with registries for other diseases and conditions.

Prevalence and prognosis of electrocardiographic left ventricular hypertrophy, ST segment depression and negative T-wave; the Copenhagen City Heart Study

AIMS

To evaluate the prevalence and the independent prognosis of electrocardiographic left ventricular hypertrophy by voltage only, ST depression and negative T wave, isolated negative T wave and left ventricular hypertrophy plus ST depression and negative T wave for cardiac morbidity and mortality, without known ischaemic heart disease at baseline.

METHODS AND RESULTS

Follow-up data from the Copenhagen City Heart Study were used. Subjects were 5243 men and 6391 women, age range 25-74 years. End-points were (1) myocardial infarction, (2) ischaemic heart disease and (3) cardiovascular disease mortality. Relative risk was age- and sex-adjusted, and multivariately adjusted for known cardiovascular risk factors. During 7 years follow-up, left ventricular hypertrophy plus ST depression and negative T wave had an age-adjusted relative risk of 3.78 (95% confidence interval 2.29-6.25) for myocardial infarction, 4.27 (2.95-6.16) for ischaemic heart disease and 3.75 (2.41-5.85) for cardiovascular disease. A negative T wave, ST depression and negative T wave changes, and left ventricular hypertrophy with negative T wave also carry independent prognostic information for myocardial infarction, ischaemic heart disease and cardiovascular disease.

CONCLUSIONS

Electrocardiographic left ventricular hypertrophy with ST depression and negative T wave changes are the electrocardiographic abnormalities with the greatest prognostic information for future cardiac events. Electrocardiographic negative T waves, ST depression and negative T wave abnormalities and left ventricular hypertrophy with negative T waves, also have prognostic information.

[Measurement of the wound cavity area by means of PC based planimetry. The method and observer variations]

A method for wound area measurement is presented. A wound cavity was cut in a chine of pork. A thin PVC plastic film was applied closely to the entire wound cavity surface and a line was drawn close to the cutaneous border with a marker pen. The film was then placed on a system of coordinates and coordinates were determined and entered into a PC-programme which calculated the area. No significant intra-or inter-observer variation appeared on analyses of variance between five observers each of whom performed three consecutive measurements (p > 0.2). Thus, employment of the method for clinical purposes seems feasible.

[Sucralfate versus placebo in the treatment of abdominal wound abscesses]

Twenty-seven patients were divided at random into two groups following abscess formation and complete reopening of the abdominal wound in a prospective double blind investigation to study the effect of topical sucralfate on the wound healing rate in secondary abdominal wounds. Fifteen patients were treated with sucralfate powder and 11 patients with placebo while one patient was excluded. The two groups were comparable as regards age, sex and factors predisposing to abscess formation. In the sucralfate group the median healing rate was 2.8 cm2/24 hours as compared with 2.4 cm2/24 hours in the placebo group (p = 0.92, Mann-Whitney test). From this investigation, it is concluded that topical application of sucralfate powder does not appear to increase the rate of healing in secondary abdominal wounds after incision of a wound abscess.

Biosynthesis of the neural cell adhesion molecule: characterization of polypeptide C

The biosynthesis of the neural cell adhesion molecule (N-CAM) was studied in primary cultures of rat cerebral glial cells, cerebellar granule neurons, and skeletal muscle cells. The three cell types produced different N-CAM polypeptide patterns. Glial cells synthesized a 135,000 Mr polypeptide B and a 115,000 Mr polypeptide C, whereas neurons expressed a 200,000 Mr polypeptide A as well as polypeptide B. Skeletal muscle cells produced polypeptide B. The polypeptides synthesized by the three cell types were immunochemically identical. The membrane association of polypeptide C was investigated with methods that distinguish peripheral and integral membrane proteins. Polypeptide C was found to be a peripheral membrane protein, whereas polypeptides A and B were integral membrane proteins with cytoplasmic domains of approximately 50,000 and approximately 25,000 Mr, respectively. The affinity of the membrane binding of polypeptide C increased during postnatal development. The posttranslational modifications of polypeptide C were investigated in glial cell cultures, and it was found to be N-linked glycosylated and sulfated.