Adjust-Unlikely pulmonary embolism testing using telephone recruitment: a pilot study to assess the feasibility of evaluating its safety and efficiency.

Background: Studies on pulmonary embolism (PE) rule-out strategies traditionally recruited patients in the ED. This method is increasingly impractical given excessive pressures experienced in EDs. Attempting to reach patients after leaving the ED may be more feasible. The aim of this study was to assess the feasibility of recruiting and following patients for an ED PE testing study by telephone.

Methods: This was a prospective pilot study conducted in one ED and one urgent care centre in Ontario, Canada. Adult patients tested for PE using Adjust-Unlikely (a simple decision rule combining Gestalt with age-adjusted D-dimer) were called for consent after leaving the ED. Patients were followed for 90 days by medical record review plus telephone, text or email to identify subsequent venous thromboembolism testing. Venous thromboembolism events were independently adjudicated. Feasibility outcomes were recruitment rate, missed eligible rate and follow-up rate. Progression criteria were a recruitment rate of at least five participants per site, per week, a missed eligible rate of no more than two patients per site, per week, and a follow-up rate of at least 90% of enrolled patients.

Results: 684 patients were tested for PE between 24 March and 10 June 2023. A total of 210 patients were excluded. From 474 eligible patients, 200 were recruited. Median age was 58 years, 72.2% were female, and 3.5% were diagnosed with PE on index visit. Median recruitment rate was 7 participants per site, per week (first-third quartile (Q1-Q3), 4-14) and median missed eligible rate was 6 patients per site, per week (Q1-Q3, 3-8). After 90 days, 2 participants withdrew and 191/198 (96.5%, 95% CI 92.9, 98.3%) were contacted in follow-up. 143/198 (72.2%, 95% CI 65.6, 78.0%) participants did not require pulmonary imaging because PE was excluded by Adjust-Unlikely. 1/143 (0.7%, 95% CI 0.1, 3.9%) of these participants was diagnosed with PE in the segmental pulmonary arteries during follow-up.

Conclusions: Telephone recruitment did not meet predefined feasibility thresholds as the missed eligible rate was high. However, the recruitment rate was higher than in previous studies, and there was minimal loss to follow-up.