Effectiveness of expiratory technique and induced sputum in obtaining good quality sputum from patients acutely hospitalized with suspected lower respiratory tract infection: a statistical analysis plan for a randomized controlled trial

BACKGROUND: Targeted antimicrobial treatment is essential to avoid unnecessary use of broad-spectrum antibiotics and antimicrobial resistance. Targeted treatment relies on a precise microbiological diagnosis — in pneumonia, this poses a challenge as the usefulness of Gram stains and cultures is highly dependent on the quality of the sputum sample. This study aims to examine adverse effects and quality of sputum samples obtained by expiratory techniques (forced expiratory technique and sputum induction) compared with tracheal suction. The hypothesis is that expiratory techniques are non-inferior to tracheal suction in obtaining samples from the lower respiratory tract. This statistical analysis plan (SAP) describes the study design, method, and data analysis of the trial to increase transparency, avoid reporting bias or data-driven analysis and increase the study’s reproducibility. METHOD: The design is a pragmatic, non-inferiority, parallel-arm randomized controlled trial including 280 patients admitted with suspected lower respiratory infection to two emergency departments. Patients are randomized to a usual care group, where sputum samples are collected by tracheal suction or to an intervention group where sputum samples are collected by forced expiratory technique and sputum induction. The statistical analysis will follow an intention-to-treat protocol. This SAP is developed and submitted before the end of recruitment, database closure, and statistical analyses. DISCUSSION: The results of this study will provide valuable knowledge to clinical practice by comparing adverse effects and sputum sample quality associated with different sample methods. TRIAL REGISTRATION: Clinicaltrials.gov, NCT04595526. Submitted on October 19, 2020 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-021-05639-1.