Assessment of observer variation in measuring the Radiographic Vertebral Index in patients with multiple myeloma.
The Radiographic Vertebral Index (RVI) was assessed as a possible outcome measure for bone disease in myeloma by evaluating within and between reader reproducibility. Four readers (2 radiologists and 2 clinical hematologists) independently scored, on two separate occasions, the RVI on 40 radiographs from patients with myeloma. Each vertebra from third thoracic (T3) to fifth lumbar (L5) received a score of "1" if normal, "2" if biconcave and "4" if crushed or fractured. RVI global scores, therefore, could vary from a minimum of 15, for no damage, to a potential maximum of 60 in which all vertebrae are collapsed. Agreement was determined for each vertebra using crude percentage agreement and the kappa statistic (which corrects for chance-expected agreement) for categorical data, and for global score using analysis of variance and calculating intra-class correlation. With increasing mean abnormality score on individual vertebrae there was a corresponding increase in kappa and reduction in crude percentage agreement. Within readers, the mean percentage agreement across all vertebrae varied from 85.6 to 90.3% and the observed differences just reach statistical significance (p = 0.048). Mean kappa values ranged from 0.48 to 0.63 and were similar across readers. Differences in intra-reader agreement were not related to subspecialty. When between reader percentage agreement and kappa scores were assessed for radiologists and non-radiologist clinicians, no difference could be detected. Agreement with respect to intra-reader mean global RVI scores was excellent as illustrated by the intra-class correlation coefficient which varied from 0.89 to 0.94. The mean intra-class correlation for radiologists was 0.92, compared with 0.91 for non-radiologists.(ABSTRACT TRUNCATED AT 250 WORDS)
Browman
G P
GP
Ontario Cancer Foundation, Hamilton Regional Centre, Hamilton Civic Hospital, Ontario, Canada.
Markman
S
S
Thompson
G
G
Minuk
T
T
Chirawatkul
A
A
Roberts
R S
RS
D000704:Analysis of Variance; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D009101:Multiple Myeloma / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D013131:Spine / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging