TY - JOUR T1 - BET 1: Everything in graduation: arterial/end-tidal CO<sub>2</sub> gradient and the diagnosis of pulmonary embolism JF - Emergency Medicine Journal JO - Emerg Med J SP - 361 LP - 363 DO - 10.1136/emermed-2021-211738.2 VL - 38 IS - 7 AU - John O'Rourke AU - Bethany MacDonald Y1 - 2021/07/01 UR - http://emj.bmj.com/content/38/7/361.abstract N2 - A short cut review was carried out to establish the diagnostic characteristics of alveolar dead space fraction (AVDSf) in the diagnosis of pulmonary embolism (PE). This is calculated from the arterial and end-tidal CO2. Three papers were selected to answer the clinical question. The author, study type, relevant outcomes, results and weaknesses are tabulated. It is concluded that there is good evidence to support the use of AVDSf within a clinical prediction model to exclude a PE in patients when there is a low pretest probability. However, the specificity is not sufficient to support it as a ‘rule in’ test. ER -