External validation of the InShape II study algorithm for exclusion of chronic thromboembolic pulmonary hypertension in patients with pulmonary thromboembolism.

Background And Aim: The most severe long-term complication of pulmonary embolism (PE) is chronic thromboembolic pulmonary hypertension (CTEPH), and its early diagnosis often requires numerous diagnostic tests. The InShape II study proposes an early screening algorithm that aims to reduce the number of echocardiographic studies. The objective of our study is to validate this algorithm in our patient cohort.

Materials And Methods: We retrospectively analyzed patients admitted to Hospital Rey Juan Carlos between November 2017 and February 2020, who were diagnosed with PE based on computed tomography angiography (CTA). Patients were followed for at least one year, and clinical, laboratory, and complementary test data were collected at three months and one year. The InShape II algorithm was applied to these patients to validate its results.

Results: During the study period, 236 patients were diagnosed with PE, of which 137 were excluded. The algorithm was validated in 99 patients. Applying the InShape II score, 19 echocardiograms would have been performed (three of them with intermediate-high probability of CTEPH), while 80 echocardiograms would have been avoided (two of them with intermediate-high probability). This yielded a sensitivity of 60% and a specificity of 83% for the score, with an area under the curve (AUC) of 0.715 (95% CI: 0.472-0.958).

Conclusions: Our results support the notion that the InShape II algorithm could be a useful tool for initial screening of CTEPH in low-incidence settings, as it would avoid unnecessary echocardiograms that do not provide additional value.