Inter-and intrarater agreement of Computed Tomographic brain calcification scoring in Primary Familial Brain Calcification.

Background and purpose: The Total Calcification Score (TCS) is a visual rating scale to measure Primary Familial Brain Calcification (PFBC) related calcification severity on Computed Tomography (CT). We investigated the inter-and intrarater agreement of a modified TCS.

Materials and methods: Patients aged ≥18 years with PFBC or Fahr's syndrome who visited the outpatient clinic of a Dutch academic hospital were included. The TCS was modified, for example by adding hippocampal calcification, and ranged from 0 to 95 points. Fifteen raters evaluated all CTs, of whom three evaluated the CTs twice. Their Entrustable Professional Activity (EPA) level ranged from II (medical student) to V (neuroradiologist). Agreement was assessed using the intraclass correlation coefficient (ICC) for the total score. Kendall's W and weighted Cohen's Kappa were used to determine the inter- and intrarater agreement for individual locations, respectively.

Results: Forty patients were included (mean age 60 years, 53% female). The median modified TCS was 34 (range 4-76). For all EPA levels, the interrater agreement of the modified TCS was excellent (ICC=0.97 (95% CI 0.95-0.98)). Kendall's W's were good to excellent for commonly affected locations, but poor to moderate for less commonly affected locations for raters with lower levels of expertise. The intrarater agreement of the modified TCS was excellent. Kappa's of most locations were substantial to almost perfect.

Conclusions: The modified TCS can be used with excellent reproducibility of the overall amount of brain calcifications and with limited training, although for some individual calcification locations more expertise is needed.

Abbreviations: CI, Confidence Interval; CT, Computed Tomography; EPA, Entrustable Professional Activity; IBGC, Idiopathic Basal Ganglia Calcification; ICC, Intraclass Correlation Coefficient; IQR, Interquartile Range; PFBC, Primary Familial Brain Calcification; SD, Standard Deviation, TCS, Total Calcification Score; UMCU, University Medical Center Utrecht.