Background: Clonal mast cell disease (CMD) is an underlying aggravating condition in wasp venom allergy (WVA) which requires a different treatment strategy. CMD is increasingly recognized in patients with normal basal serum tryptase (bsT). However, methods to identify at risk patients have not yet been assessed in large cohorts of WVA patients with normal bsT. Methods: This retrospective study evaluated the reliability of the REMA score in detecting CMD in a cohort of grade IV WVA patients with normal bsT and assessed the added value of other clinical parameters, KIT D816V mutation analysis in peripheral blood (PB) and the diagnosis of hereditary alpha tryptasemia (HAT). All patients had a conclusive bone marrow evaluation that demonstrated or excluded underlying CMD.Results: In total 35 CMD and 96 non-CMD patients were included. REMA score had a sensitivity of 72% (95% CI 56%-88%) and specificity of 79% (95% CI 70%-87%) in this cohort. Loss of consciousness during systemic reaction and bsT between 6.3 and 11.4 ng/ml were additional parameters independently associated with CMD.Sensitivity of KIT in PB was relatively low, 56% (95% CI 36%-75%), but had added value as screening method in patients with a low REMA score due to 100% specificity. Conclusion:The REMA score is a relatively reliable method to detect patients at risk of CMD among WVA patients with normal bsT. KIT mutation analysis in PB could serve as additional screening method in patients with low REMA scores. K E Y W O R D Sinsect venom, KIT D816V analysis in peripheral blood, mastocytosis, REMA score, tryptaseThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Objectives To determine the proportions of abdominal US examinations during on-call hours that are negative and that contain an incidentaloma, and to explore temporal changes and determinants. Methods This study included 1615 US examinations that were done during on-call hours at a tertiary care center between 2005 and 2017. Results The total proportion of negative US examinations was 49.2% (795/1615). The total proportion of US examinations with an incidentaloma was 8.0% (130/1615). There were no significant temporal changes in either one of these proportions. The likelihood of a negative US examination was significantly higher when requested by anesthesiology [odds ratio (OR) 2.609, P = 0.011], or when the indication for US was focused on gallbladder and biliary ducts (OR 1.556, P = 0.007), transplant (OR 2.371, P = 0.005), trauma (OR 3.274, P < 0.001), or urolithiasis/postrenal obstruction (OR 3.366, P < 0.001). In contrast, US examinations were significantly less likely to be negative when requested by urology (OR 0.423, P = 0.014), or when the indication for US was acute oncology (OR 0.207, P = 0.045) or appendicitis (OR 0.260, P < 0.001). The likelihood of an incidentaloma on US was significantly higher in older patients (OR 1.020 per year of age increase, P < 0.001) or when the liver was evaluated with US (OR 3.522, P < 0.001). Discussion Nearly 50% of abdominal US examinations during on-call hours are negative, and 8% reveal an incidentaloma. Requesting specialty and indication for US affect the likelihood of a negative examination, and higher patient age and liver evaluations increase the chance of detecting an incidentaloma in this setting. These data may potentially be used to improve clinical reasoning and restrain overutilization of imaging.