Agreement of liver iron quantification measurements with low Tc-SQUID biosusceptometers in Oakland, Torino and Hamburg

.Accurate measurement of liver storage iron is important for the management of iron overload from regular red blood cell transfusion therapy. In clinical trials testing iron chelator efficacy in iron overloaded patients, with different centers involved, it is mandatory to standardize the procedures of liver iron concentration (LIC) measurements.The agreement (precision and bias) of the SQUID biosusceptometer in Oakland/USA (CHO) and Torino/Italy (TOR) was evaluated in comparison to the validated System in Hamburg/Germany (UKE). In a blinded round-robin test, liver iron concentrations were quantified within 1 month by the 3 SQUID biosusceptometer systems, in 20 patients with thalassemia, sickle cell disease or CDA type-1 and in 10 normal subjects.Mean LIC values were determined from 5 vertical scans at each of two, different positions. Prediction of LIC at CHO and TOR in comparison with UKE was excellent, with coefficients of determination between sites of R2 = 0.97, resulting in inter-site standard deviations of 276 and 315 μg/g liver, respectively. A significant proportional underestimation of 27% was noted for the TOR system. A systematically lower skin–liver distance of 1.0 mm at the TOR site could only account for 10% of the underestimated LIC. Intra-site precision was within an acceptable range for repeated measurements in the majority of iron overloaded subjects.