Identifying Ontario geographic regions to assess adults who present to hospital with laboratory-defined conditions: a descriptive study

Abstract

Background: In 2007, an electronic repository called the Ontario Laboratories Information System (OLIS) was introduced to allow health care providers timely access to laboratory test results. Since not all laboratories began submitting their data to OLIS simultaneously, we sought to create a date-dependent table of geographic regions (forward sortation areas [FSAs]) from which people would likely present to a hospital linked to OLIS. Methods: In this descriptive study, we used administrative data to capture adults in Ontario who presented to the emergency department for any reason from 2007 to 2017. To assess changes over time, we classified all emergency department visits into fiscal quarters. The primary outcome measure was the proportion of people in a given FSA presenting to an emergency department at an OLIS-linked hospital (v. a hospital not linked to OLIS). To be included in the catchment area, at least 90% of all emergency department visits in a given quarter from a given FSA must have occurred at an OLIS-linked hospital. Results: By Dec. 31, 2017, 323 (61.4%) of 526 Ontario FSAs were in the catchment area (a population of about 8.5 million). There were no differences in selected demographic characteristics or comorbidities between people residing within the catchment area of OLIS-linked hospitals and those residing in the catchment area of unlinked hospitals on Dec. 31, 2017. We used the FSA information to construct a date-dependent table of geographic areas likely to have hospital laboratory data available in OLIS for future studies. Interpretation: We identified relevant Ontario geographic regions from which people would likely present to a hospital linked to OLIS. These geographic regions constitute a catchment area that may be used in future studies to capture adults who present to an OLIS-linked hospital with laboratory-defined conditions such as acute kidney injury, hyperkalemia and hyponatremia.

Use of sodium–glucose cotransporter-2 inhibitors and risk of acute kidney injury in older adults with diabetes: a population-based cohort study

“…Study participants were assigned to geographic hospital catchment areas with corresponding linked laboratory data, using previously published methods. 29 We included only Ontarians who resided within these catchment areas to ensure accurate ascertainment of outcomes, as not all hospital-based laboratories started contributing to Ontario Laboratories Information System (OLIS) at the same time and, to date, not all are contributing.…”

“…To ascertain outcomes accurately for participants in our cohort, we ensured that participants resided within areas serviced by OLIS, so that they would receive serum creatinine tests in hospitals captured in our data source. 29 In terms of accuracy and completeness, OLIS values for serum creatinine levels are preferable compared with diagnostic codes, and once a hospital begins contributing to OLIS, the database should have complete capture of all test results. For baseline serum creatinine measurement, we selected an outpatient value (measured by outpatient community or hospital laboratories) within the past year that was closest to their index date.…”

Diabetes after pregnancy: a study protocol for the derivation and validation of a risk prediction model for 5-year risk of diabetes following pregnancy

“…Since the OGCT is offered to all pregnant women and screening rates are high in Canada [ 49 ], missing data in this variable should predominantly relate to whether the attending site was contributing submissions to OLIS. Given that evidence suggests no differences in characteristics of people attending OLIS contributing and non-contributing sites [ 50 ], it may be reasonable to assume that these data are missing completely at random, in which case multiple imputation is an appropriate missing data handling approach [ 41 ]. However, exploratory analyses will be undertaken to determine whether OGCT values can be reasonably imputed using available data.…”

Trends in basal insulin prescribing in older adults with chronic kidney disease in Ontario, Canada: A population‐based analysis from 2010 to 2020

“…creatinine and HbA1c) for provincial laboratories within the OLIS catchment area. 21 A list of our coding definitions is included in Table S2.…”