Successful and safe implementation of a trinary interpretation and reporting strategy for V/Q lung scintigraphy

Objectives For the past three decades, V/Q scan interpretation was categorized using probability assessments that were not well received or understood by all referring physicians. In a recent publication, we combined normal, very low and low probability interpretations yielding a FN rate on follow-up of only 1.2% vs. 1.1% for CTPA in ER patients. Therefore, we changed to a new trinary interpretative strategy (no PE, PE present and non-diagnostic scans). In this series, we analyze the outcomes of the trinary system.

Methods We retrospectively identified all patients who underwent V/Q scans for 1-year (probability interpretation: 9/18/08-3/17/09; trinary interpretation: 3/18/09-9/17/09). A clear chest x-ray was generally used to triage the patients. Medical record follow-up for negative V/Qs was performed to determine if DVT or PE developed within 3-months after baseline evaluation (false negative-FN).

Results Standard probability interpretations (n=796) reported 45 (5.7%) high, 33 (4.1%) intermediate, and 718 (90.2%) low, very low or normal probabilities. New trinary interpretation (n= 654) resulted in 63 (9.6%) positive, 569 (87%) negative and 22 (3.4%) non-diagnostic scans. FN rate for 3-month follow-up utilizing standard interpretation was 1.25% (9/718, 8 DVT and 1 PE) compared to 1.58% (9/569, 5 DVT and 4 PE) utilizing the trinary interpretation system (p=0.7).

Conclusions A simplified trinary interpretation strategy for V/Q lung scintigraphy provides outcomes similar to standard probability assessments. This system facilitates clearer communication with referring physicians and can be safely implemented