To the Editor.
—Deyo et al1 report on the importance of history and physical examination findings in the assessment of patients with back pain. They are to be commended for emphasizing the limitations of expensive imaging studies in these patients and for identifying those historical and examination features that should be most helpful to the clinician. Their efforts to define a new pair of operating characteristics for test performance deserve scrutiny, however.The authors define "SpPin" as an acronym to remind the clinician that "when specificity is extremely high, a positive test result rules in the target disorder." But the authors' own data demonstrate that one can have a very high test specificity without a high positive predictive value. Consider, for example, the authors' data regarding use of fever as a test for spinal infection. Prevalence is defined as 0.01%, sensitivity is 0.83 for spinal epidural abscess, and specificity
Kelleher M. Back Pain: The History and Physical Examination. JAMA. 1993;269(3):355. doi:10.1001/jama.1993.03500030052020