Post-test probability for pulmonary embolism after ventilation-perfusion scan assessed by nuclear medicine physicians

Objective: The objective of this prospective study was to compare assessments of pre- and post- ventilation- perfusion ( V/ Q) scan probabilities for pulmonary embolism ( PE) by the nuclear medicine physician and the referring physician. Materials and Methods: Seventy- nine patients ( 41 females, 38 males, mean age 49 years) referred for V/ Q scans over a period of 6 months and suspected of PE were included in the study. The pre- test likelihood was determined independently by a consultant nuclear physician and a referring physician prior to the V/ Q scan. The scan was performed according to a standard protocol using 8 view technetium- 99m diethylenetriamine pentaacetic acid aerosol ventilation study followed by a technetium- 99m macroaggregated albumin perfusion study. The scan was interpreted according to prospective investigation of pulmonary embolism diagnosis criteria. The post- scan probability was calculated. The probability of PE was quoted as low, intermediate and high. Agreement or disagreement in assessing the pre- and post- scan probability was classified according to the degree of difference ( no difference: 0; minor difference: 1, and major difference: 2 grades). Results: The agreement between the nuclear medicine and referring physicians on clinical probability of PE was moderate ( 63%) before the scan and good ( 90%) after the scan. The disagreement in assessing the clinical probability between the referring physician and the nuclear medicine physician was predominantly minor. Only 5 and 1% of the disagreement was major in pre- scan and post- scan probabilities, respectively. Conclusion: The data show that nuclear medicine physicians can use the assessment of pre- scan clinical likelihood to determine the post- scan probability of PE. Copyright (C) 2005 S. Karger AG, Basel.