ESPE Abstracts

Introduction: Congenital hyperinsulinism (CHI) is a rare but severe condition causing persistent hypoglycaemia. Approximately 30-40% of patients require surgical treatment. Extent of surgery depends on the histological form of the disease: subtotal pancreatectomy is done in diffuse CHI, whereas pancreatic resection is recommended in focal CHI.¹⁸F-DOPA PET scan is a gold-standard imaging technique that helps in differential diagnosis of diffuse and focal forms with the use of special calculated parameter – pancreatic index (PI). Despite its advantages, the test has its obstacles and may result in misdiagnosis. Other new imaging techniques are unavailable in the majority of countries and require further investigation. Thus, the objective of our study is to improve diagnostic accuracy of the¹⁸F-DOPA PET.

Materials and methods: We analyzed¹⁸F-DOPA PET data in consecutive CHI patients with confirmed histological forms over a 4-year period. All but one children carry pathogenic variants in ABCC8/KCNJ11 genes. Dynamic¹⁸F-DOPA PET scans were done on “Discovery 710” scanner (General Electric). PI was calculated in pancreatic head, body, and tail 10-20, 30-40, 40-50, and 50-60 minutes after¹⁸F-DOPA injection. We plotted a ROC curve for pancreatic indexes to obtain optimal cut-off for differential diagnosis.

Results: The study included 19 patients with diffuse CHI and 14 patients with focal CHI. We discovered that commonly accepted PI cut-off of 1.5 for focal CHI lacks diagnostic accuracy (85%, CI: 67-94%) and has broad confidence interval for specificity (100%, CI: 66-100%). Our findings suggest that more accurate cut-off for focal form is 1.31 registered 30-40 minutes after¹⁸F-DOPA injection: diagnostic accuracy 91% (CI: 74-98%) and specificity 100% (CI: 81-100%). Further research revealed the highest accuracy can be achieved by a combination of the latter cut-off and visual evaluation performed by experienced radiologist: diagnostic accuracy 97% (CI: 82-100%) and specificity 95% (CI: 74-100%). For example,¹⁸F-DOPA PET scan in one of the patients with diffuse CHI showed PI of 1.47 that generally implies focal CHI. This situation could have resulted in unsuccessful pancreatic resection. However, based on our findings PI calculated 30-40 minutes after the injection was 1.11 that indicated diffuse form of the disease (as it is lower than proposed cut-off 1.31). Eventually, the patient underwent successful subtotal pancreatectomy.

Conclusion: ¹⁸F-DOPA PET plays a crucial role in the diagnosis of the histological form of CHI. Reassessment of ¹⁸F-DOPA PET cut-offs may preclude misdiagnosis and tailor surgical treatment.