Background: Workplace bullying has been measured in many studies to investigate mental health issues. None uses online computerized adaptive testing (CAT) with cutting points to report bully prevalence at workplace. Objective: To develop an online CAT to examine person being bullied and verify whether item response theory-based CAT can be applied online for nurses to measure exposure to workplace bullying. Methods: A total of 963 nurses were recruited and responded to the 22-item Negative Acts Questionnaire-Revised (NAQ-R). All non-adaptive testing (NAT) items were calibrated with the Rasch rating scale model. Three scenarios (i.e., NAT, CAT, and the randomly selected method to NAT) were manipulated to compare their response efficiency and precision by comparing (i) item length for answering questions, person measure, (ii) correlation coefficients, (iii) paired t tests, and (iv) estimated standard errors (SE) between CAT and the random to its counterpart of NAT. Results: The NAQ-R is a unidimensional construct that can be applied for nurses to measure exposure to workplace bullying on CAT. CAT required fewer items (=8.9) than NAT (=22, an efficient gain of 60% = 1-8.9/22). Nursing measures derived from both tests (CAT and the random to NAT) were highly correlated (r = 0.93 and 0.96) and their measurement precisions were not statistically different (the percentage of significant count number less than 5%) as expected, but CAT earns smaller person measure SE than the random scenario. The prevalence rate for nurses was 1.5% (= 15/963) when cutting points set at -0.7 and 0.7 logits. Conclusion: The CAT-based NAQ-R reduces respondents' burden without compromising measurement precision and increases endorsement efficiency. The online CAT is recommended for assessing nurses using the criteria at -0.7 and 0.7 (or <30 and <60 in summed score) to identify bully grade as one of the three levels (high, moderate, and low). The bullied nurse can get help from a psychiatrist or a mental health expert at an earlier stage.
