The scratch test for identifying the lower liver edge is at least as accurate as percussion and is significantly more...

Clinical examination of the liver requires experience to achieve accuracy. The scratch test is a simple technique to identify the lower liver edge and enhance liver palpation, and may be easier for trainees.

We aimed to evaluate the accuracy of the scratch test compared to percussion at different levels of medical training.

Eight examiners, from trainee intern to consultant level, were randomised to scratch or percussion testing, followed by liver palpation, on 50 subjects. Later, each examiner performed the alternative test on each subject. Confidence with each test was rated 0-3 (unsuccessful-very confident). Ultrasound scan (US) was performed as a reference for liver location.

Ultrasound revealed 33/50 (66%) of livers extended below the right costal margin in the midclavicular line during quiet respiration (range 0.5-16cm). Of these, 33, 87% and 76% were identified within 2cm of the US location using scratch and percussion tests, respectively (p>0.05) for all examiners, but with significantly greater accuracy for the scratch test in young trainees (91% v 75%; p=0.016). Ability to palpate the liver was not different following either test. The training effect was assessed by comparing the accuracy results of the first 25 with the last 25 examined subjects, revealing a significant increase in accuracy with percussion from 71% to 85% (p=0.038) compared to no change with the scratch test (88% and 86%). Examiner confidence in the test result was significantly higher using the scratch test versus percussion, average confidence scores being 2.2 versus 1.8 (p<0.001), with a greater difference in the young trainee group at 2.4 versus 1.7 (p<0.001).

The scratch test was at least as accurate as percussion overall in identifying the lower liver edge and significantly more accurate for the young trainees. The scratch test requires less training and in addition, all examiners and especially the young trainees were significantly more confident in their findings using the scratch test.