Tr. Jenkinson et al., DEFINING SPINAL MOBILITY IN ANKYLOSING-SPONDYLITIS (AS) - THE BATH ASMETROLOGY INDEX, Journal of rheumatology, 21(9), 1994, pp. 1694-1698
Objective. To determine the most appropriate clinical measurements for
the assessment of ankylosing spondylitis (AS) and to develop the new
metrology index.Methods. One hundred and ninety-three individuals with
AS were studied. The patients reflected the entire spectrum of cases
of AS. Metrology was performed on 327 occasions. First the metrology (
20 measurements) of 43 patients was analyzed. From this, 5 simple clin
ical measurements were defined which most accurately reflect axial sta
tus: cervical rotation, tragus to wall distance, lateral flexion, modi
fied Schober's, and intermalleolar distance. These measurements were a
ssessed for reliability, speed and both inter and intraobserver variab
ility in another 40 patients. Results. Analysis of the first group of
43 patients and a subsequent group of 54 patients, using the 5 measure
ments that constitute this new Bath AS Metrology Index (BASMI), demons
trated that they accurately and reliably mirror the 20 clinical measur
ements assessed previously (r = 0.92, p <0.001). In a new group of 40
patients the measurements were demonstrated to be accurate and reprodu
cible for both intraobserver variability (r = 0.99, p <0.001) and inte
robserver variability (r = 0.97, p <0.001). In a further 56 patients,
admitted for inpatient therapy, an improvement in the BASMI from 3.34
(SD 2.71) to 2.16 (SD 2.42) was noted over a period of 3 weeks (regard
less of disease severity) which indicates a sensitivity to change (X(2
) = 6.55, P <0.01). The mean improvement over baseline was about 30%.
Conclusion. Five clinical measurements provide a composite index (BASM
I) and define disease status in AS. The BASMI is quick (7 min), reprod
ucible and sensitive to change across the disease spectrum.