To develop and evaluate a modification of the Larsen scoring method aimed at a clear definition of the different grades and a better correlation of the numerical scale with the amount of joint destruction.
While the original method described by Larsen is based on a comparison with standard reference films the modification defines the different grades semiquantitatively by the amount of destruction of the joint surface: grade II is a destruction (erosion) of the joint surface of up to 25%, in grade III it is 26-50%, in grade IV 51-75% and in grade V over 75%. Grade I is characterized by soft tissue swelling and in addition subchondral osteoporosis and remains unchanged compared with the original method. 32 joints of the hands, wrists and forefeet are counted summing up to a total score of 0-160. Examples for different joints are given.
Standard ap-x-rays of hands, wrists and forefeet of 24 patients with early erosive rheumatoid arthritis at baseline (T0) and after 36 months (T1) were graded by two investigators (G.H. and R.R.). The difference of the scoring between both observers (inter-observer-difference) was related to the difference between the two timepoints (T0 and T1) in the same patient (intra-patient-difference) by means of a hierarchical analysis of variance (ANOVA). The intra-patient variance (from T0 to T1) was 259.3, which is 8 times greater than the inter-observer-variance of 32.1. The square root of intra-patient-standard deviation (16.1) and inter-observer-standard deviation (5.7) is 2.8. These data show that the progression between T0 and T1 is real. The method was easily applicable to patients in a 2-year-DMARD-trial with x-rays at baseline after 6, 12 and 24 months, showing a slowing of radiologic progression after month 6 under treatment with parenteral gold and methotrexate.
The modification of Larsen's scoring method is a reliable measure to assess radiologic progression in patients with RA. Possibilities for further improvement are discussed.