Bleeding risk with antiplatelet use during thoracentesis: systematic review with confounder matrix

<bold>Background:</bold> While thoracentesis is considered a low bleeding risk procedure, many patients with pleural effusion have cardiovascular comorbidities indicating antiplatelet use. Several recent guidelines on pleural procedures make no mention of antiplatelets. Ethical concerns preclude the conduct of randomized trials to address this question. <bold>Objective:</bold> This study aimed to determine the safety of antiplatelet use in terms of bleeding risk among adults undergoing thoracentesis. <bold>Methods:</bold> A systematic review of non-randomized studies of interventions was conducted to estimate the effect of current antiplatelet use on bleeding risk in adults undergoing thoracentesis. A causal directed acyclic graph was constructed by pulmonary medicine content experts and a methodologist to assess confounder control for the primary outcome of any bleeding event. Electronic databases (PubMed, Cochrane Library and CINAHL) were queried using text words and subject headings for observational studies until 15 February 2024. Characteristics and outcome data were extracted from eligible studies. The Newcastle-Ottawa Scale was used to assess study quality. Random-effects meta-analyses using the generic inverse variance method were performed using Review Manager 5.4. <bold>Results:</bold> Seven cohort studies (n = 2,380) with moderate risk of bias were included. Most involved patients receiving clopidogrel in the exposure group. None adequately adjusted for confounders. Pooled analysis from 3 studies showed that bleeding events were increased with antiplatelet use (OR 2.68, 95% CI 1.05-6.79, I2 = 0%). <bold>Conclusion:</bold> Very low certainty evidence suggests that bleeding risk is increased with antiplatelet use when performing thoracentesis.