The sensitivity and specificity of pain response to activity and position in categorizing patients with low back pain

The purposes of this study were to develop screening tests for four low back pain (LBP) diagnoses based on patient reports concerning the severity of pain in various positions and during activities and then to examine the accuracy of these tests in assigning subjects to one of four LBP diagnostic categories. The accuracy of screening tests is determined by calculating sensitivity and specificity and is well established in epidemiology.

One hundred six consecutive patients who either were being treated for LBP for the first time or had not received medical care for LBP at the participating clinics within the 12 months prior to the study were recruited.

Subjects completed a Pain Response to Activity and Position Questionnaire at the time of their initial clinic visit. The diagnosis of LBP was obtained from the medical record after at least 1 month of follow-up and the completion of diagnostic testing. Data analysis yielded symptom clusters that were used to produce screening tests for each of the four categories of LBP.

Sensitivity, specificity, and positive and negative predictive power of the screening tests were (1) benign back disease: .57,.71,.40, and .82, (2) disk disease: .65,.49,.35, and .77, (3) spinal stenosis: .52, .74, .36, and .85, and (4) disk disease with spinal stenosis: .81, .54, .24, and .94.

Although more than half of the subjects with a particular LBP diagnosis tested positive for that diagnosis, approximately two thirds of the subjects who tested positive for each of the diagnoses actually had another diagnosis. Negative tests may be more useful in that between 77% and 94% of the subjects without the diagnosis tested negative. Although patient reports of LBP response to position and activity are not sufficient for diagnosis, they may be useful in ruling out a particular diagnosis.