In Ontario, 33,788 OFCs were performed during the study period. There were 24,423 OFCs (72.24%) performed in community clinics and 9384 (27.76%) performed in hospital (Additional file 1: Table S1). Hospital OFCs were generally performed by younger physicians (average 41.0 ± 8.0 y) than those performed in community (47.2 ± 10.4y) (p < 0.00001). They were also more frequently performed by female physicians (42%) compared to those performed in community setting (34%) (OR = 1.43, p < 0.0005).

In Québec, 20,716 OFCs were billed during the study period, all of which were performed in hospital where currently there is no billing code available for office-based challenges. Physician demographics were not available. About 51% of OFCs were billed under the hybrid remuneration plan involving a baseline salary and partial fee-for-service whereas the rest were billed using traditional fee-for-service plan. For Québec hospitals, 61% of OFCs were performed in children younger than 15 years old, compared to 72% in Ontario hospitals and 59% in Ontario community clinics. In the pediatric population, 58%, 59% and 57% were performed in male patients in Québec hospitals, Ontario hospitals and Ontario clinics, respectively, compared to 38%, 38% and 29% in the adult population (Fig. 1). In both provinces, there was a steady increase in the number of OFCs performed annually (Fig. 1). Over the 5-year period studied, the number of OFCs increased by 92% and 85% in Ontario clinics and Québec hospitals, respectively. Whereas for Ontario hospitals, the number of OFCs almost tripled at a 194% increase. In both Québec and Ontario, there was large variability in the total number of OFCs performed by each physician individually, with the majority of OFCs being performed by less than a quarter of allergists (Fig. 1).

Oral Food Challenges in Québec and Ontario between 2013 and 2017. A, D and G present the number of oral food challenges (OFCs) performed in male (blue) vs female patients (red) according to age groups, in Québec hospitals, Ontario hospitals and Ontario clinics during the study period. B, E and H indicate the number of OFC performed for each year. C, F and I present the average number of OFCs performed per year by physicians in the two provinces. Each portion of the pie charts indicates the proportion of physicians with the various productivity. Physicians who performed an average of less than 1 OFC per year were excluded

Heat Map demonstrating number of total OFCs conducted annually per 100,000 residents in Ontario and Québec

In Ontario, approximately 50% of all OFCs were performed in 3 LHINs: Waterloo Wellington at 17.89%, Toronto Central at 17.09% and Central at 11.49%, respectively. However, the most densely populated LHINs were Hamilton Niagara, Central East and Champlain. In Québec, the majority of OFCs were performed in Montréal totalling 52.95% of the province’s OFCs (Fig 2, Tables 1 and 2).

The geographical difference was even more striking when considering the rate of OFCs performed per 100,000 residents, annually (Additional file 1: Table S2 and S3). In Ontario, Waterloo-Wellington LHIN had a rate of 156 OFCs per 100,000 residents per year—well above Toronto Central and Erie St. Clair’s annual rates at 89 and 84 OFCs per 100,000 residents, respectively (Fig. 3). When looking at the number of practicing allergists per LHIN, Hamilton Niagara, Toronto Central and Central LHINs had the most allergists at 19, 18, 18 allergists each, respectively (Fig. 4). Across Ontario, the average number of OFCs conducted annually per 100,000 residents was 49 challenges. Similarly, the average number of OFCs performed annually per 100,000 residents in Québec across all the administrative regions was 50, with 110 OFCs performed annually per 100,000 residents in Montreal, followed by 70.6 and 69.9 OFCs in Laval and Capitale-Nationale, respectively (Fig. 3). When looking at the number of Allergists per Administrative Region in Québec–Montreal, Capitale-Nationale and Montérégie had the most allergists at 37, 10 and 7 each, respectively (Fig. 4).

Heat Map demonstrating number of clinic and hospital-based OFCs conducted annually per 100,000 residents in Ontario

Heat map demonstrating the number of Allergists practicing per LHIN in Ontario and per Administrative Region in Québec

For both Québec and Ontario, the rate of OFCs was strongly correlated with the number of allergists having hospital privileges in the corresponding administrative regions and LHINs (R2 = 0.98). There were a few administrative regions with no allergists who had OFCs performed by specialists who had hospital privileges such as pediatricians (Fig. 5).

Correlation between number of allergists with hospital privileges and number of OFC performed in an administrative region for the provinces of Québec and Ontario