Bone marrow fibrosis: histomorphometric analysis and interobserver reproducibility of a simple optical method of...

A histomorphometric analysis of the length of reticulin fibres per area of haemopoietic bone marrow was performed on 59 trephine iliac crest biopsies. The values obtained were found to correlate with the degree of fibrosis as determined by a simple optical method based on the degree of microscopic magnification required for recognition of the presence of reticulin fibres. The mean length of fibre (microns/10,000 micron2) for the three degrees of fibrosis defined by the optical method were: 241.8 +/- 16.6 for grade I, 713 +/- 85.6 for grade II, and 1827.9 +/- 230.4 for grade III (P < 0.001). In a series of 67 biopsies, the overall interobserver agreement of the optical method was found to be good (Spearman's r = 0.99; P < 0.001) and there was good individual agreement for each of the three degrees of fibrosis (improved kappa test). There was a small amount of overlap between the extreme values of adjacent optical degrees. These results suggest that the optical method described here can be recommended as a practical technique for the routine evaluation of myelofibrosis.