A-220 Preanalytical factors contributing to indeterminate QuantiFERON-TB Gold Plus results: a showcase of data-driven root cause analysis

Abstract Background Targeted testing for tuberculosis (TB) is recommended for individuals at increased risk of TB exposure and progression to active TB. Interferon-gamma release assays (IGRA), such as QuantiFERON-TB Gold Plus (QFT-Plus), are widely used for TB screening due to their advantages over traditional skin tests. However, minimizing preanalytical factors that lead to inaccurate results is crucial for TB blood tests to avoid unnecessary testing and potential delay in patient care. Analytical and preanalytical factors, along with patient conditions, can cause indeterminate QFT-Plus results. Studies have shown varying rates of indeterminate results across different patient populations, with higher rates in immunocompromised patients or those on immunosuppressive medications. Common preanalytical errors include under or overfilling tubes, tube mix-ups, and deviations in storage or incubation times, all of which can lead to inaccurate QFT-Plus test results. This study showcases a root cause analysis (RCA) process that identifies preanalytical errors causing increased indeterminate results on QFT-Plus test performed in a safety net hospital laboratory. Methods The QFT-Plus assay involves testing blood in four tubes (Nil, mitogen, TB1, TB2) pre-coated with specific TB antigens, generating qualitative results (positive, negative or indeterminate) based on the numeric values obtained from each tube. The laboratory noticed an increased rate of indeterminate results on specimens collected from a remote site. Despite communication on proper specimen collection and handling, the issue persisted, prompting a root cause analysis (RCA) and development of corrective action. In order to identify the likely source of error, data on monthly indeterminate rates from three patient groups (occupational screening, all patients tested, the remote site of interest) were analyzed. Trends and discrepancies were assessed, and individual collectors* performance was further evaluated. Results Initial analysis of six months of data revealed indeterminate rates of 5-13% for all patients tested, 2-5% for occupational screening population, and 1-5% for the remote site (except for 10% in the last month). Consistent rates in other patient groups suggested instrument performance was not the issue. Based on the patient population and up trending on indeterminate rate for the remote site on the last month’s data, it was determined that preanalytical factors were likely the causes. Further analysis showed reduced indeterminate rates for most collectors after initial communication of proper protocols, except one with inconsistent performance and a 38% indeterminate rate at one point. Direct observation identified occasional practices of specimen pouring-over among tubes to avoid under or overfilling. Re-education led to significant indeterminate rate reduction. Additionally, the study highlighted the importance of continuous monitoring and training to ensure accurate results. Conclusion The preanalytical phase is a challenging area for error detection and correction, as preanalytical errors often occur outside the laboratory. This study demonstrated a data-driven RCA that identified and resolved preanalytical errors led to inaccurate QFT-Plus results, preventing unnecessary retesting and delays in patient care. Furthermore, the data will help establish metrics for ongoing monitoring of preanalytical factors impacting test results. Continuous education and adherence to proper specimen handling protocols are essential to ensure accurate TB screening and improve patient outcomes.