A unidimensional pain/disability measure for low-back pain syndromes.

A new measure is presented, suitable for documenting severity and response to treatment in chronic low-back pain syndromes. It is self-administered and combines two pain and seven mobility items. These were selected from pre-existing validated instruments on the basis of their sensitivity to change after treatment. Their Italian validated translation was adopted. The measure was administered to 32 chronic low-back pain Italian patients, all refractory to previous conservative treatments. In most cases they presented with herniation or protrusion of 1-3 lumbar discs. Patients were treated with 3-6 sessions of autotraction over a 5- to 15-day period. Scores on the scale were recorded at admission, discharge and follow-up, 1-3 months after treatment. At discharge and at follow-up, patients were asked if, overall, they felt improved, the same or worse. At follow-up, 20 patients out of 32 reported overall improvement. Scalometric properties of the measure were tested using Rasch analysis. For admission and follow-up, items followed a consistent hierarchical relationship along a unidimensional pain/disability variable, which is being called back illness. The items were not redundant, in that they spread well along a wide range of difficulty/severity. The hierarchy matched well with the expected expression of the conditions of the patients. A study was conducted on 34 chronic back pain patients, showing satisfactory test-retest reliability. Depending on the various items, Cohen's unweighted K ranged from 0.27 to 0.78, with ten of the 11 items above the 0.45 level of acceptability, while intraclass correlation coefficients ranged from 0.42 to 0.89. At follow-up, changes in BACKILL of plus 15% or more, with respect to admission, were consistent with patients' reports of improvement in 19 out of 20 cases. Changes in BACKILL of less than 15% were consistent with patients reports of being the same or worse in 11 out of 12 cases.