PRONE INSTABILITY TEST (PIT) FOR RADIOLOGICAL LUMBAR "INSTABILITY": Fritz et al. (2005) have evaluated the PIT regarding its validity and reliability in comparison with the "gold standard" of radiological lumbar "instability" and found a good reliability of 0.69 (kappa), but a low sensitivity of 61% and a low specificity of 57% (calculated). Be aware thought that radiological findings often don't correlate well with clinical findings. So while this test is not validated for radiological lumbar "