The 'anatomic shunt test' in clinical practice; contemporary description of test and in-service evaluation.

The 100% oxygen shunt test for detecting right-to-left anatomical shunting was originally described 70 years ago. However, its clinical value is not yet established. We conducted an audit in 80 patients undergoing the test between 1996 and 2012 in a tertiary referral centre. A significant difference (p=0.02) existed between the median shunt percentages where anatomical shunting was identified (10.2%) and absent (5.0%). The area under the curve for a ROC plot was 0.70. A shunt percentage of 8.3 had a sensitivity of 80% and specificity of 75% for detection of an anatomic shunt. We conclude the test is satisfactory for the first-line investigation for anatomic shunting.